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CL4.9

EDI
Arctic changes – processes and feedbacks in climate, ocean and cryosphere

The Arctic Realm is changing rapidly and the fate of the cryosphere, including Arctic sea ice, glaciers and ice caps, is a source of concern. Whereas sea ice variations impact the radiative energy budget, thus playing a role in Arctic amplification, the Greenland Ice Sheet retreat contributes to global sea level rise. Moreover, through various processes linking the atmosphere, ice and ocean, the change in the Arctic realm may modify the atmospheric and ocean circulation at regional to global scales, the freshwater budget of the ocean and deep-water formation as well as the marine and terrestrial ecosystems, including productivity. The processes and feedbacks involved operate on all time scales and it require a range of types of information to understand the processes, drivers and feedbacks involved in Arctic changes, as well as the land-ocean-cryosphere interaction. In this session, we invite contributions from a range of disciplines and across time scales, including observational (satellite and instrumental) data, historical data, geological archives and proxy data, model simulations and forecasts, for the past, present and future climate. The common denominator of these studies will be their focus on a better understanding of mechanisms and feedbacks on short to long time scales that drive Arctic and subarctic changes and their impact on climate, ocean and environmental conditions, at regional to global scales, including possible links to weather and climate outside the Arctic.

Co-organized by CR7/OS1
Convener: Marit-Solveig Seidenkrantz | Co-conveners: Anne de Vernal, Michal Kucera, Henrieka DetlefECSECS, Katrine Elnegaard HansenECSECS
Presentations
| Thu, 26 May, 15:10–18:30 (CEST)
 
Room F2

Thu, 26 May, 15:10–16:40

Chairpersons: Marit-Solveig Seidenkrantz, Anne de Vernal, Katrine Elnegaard Hansen

15:10–15:11
Welcome to this session

15:11–15:17
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EGU22-619
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On-site presentation
Claude Hillaire-Marcel et al.

The revised late Pleistocene chronostratigraphy of the Arctic Ocean based on the pre-2000 magnetostratigraphic interpretation and chronological information from the decay of U-series daughter isotopes in sediments leads to reassigning "warm" vs "cold" climatostratigraphic intervals to distinct interglacial, interstadial, or stadial stages and shows a realistic linkage with high latitude insolation parameters and the global sea-level history. "Warm" episodes then match intervals with summer season insolation and sea-level elevation peaking above those of the early Holocene. Whereas the whole summer season insolation governs heat fluxes towards the Arctic Ocean, in relation with the North Atlantic Water inflow, sea level plays a complementary role as it governs the submergence of the Arctic Ocean shelves and the development of “sea-ice factories”. Sea level also controls the flux of warm and low-salinity Pacific water through the shallow Bering Strait, thus the heat budget of the Western Arctic and the salinity budget of the whole Arctic Ocean. The combination of both parameters indicates that climate conditions during recent interglacials were of distinct amplitude and timing vs those at lower latitudes. From MIS 10 to MIS 1, five short "warm" intervals (MIS 1, 3, 5e, 7, 9) were characterized by sea-ice rafting deposition of smectite and detrital carbonate-rich sediments with 230Th-excesses along major drifting sea-ice routes TransPolar Drift; Beaufort Gyre). These layers alternate with coarser layers linked to sporadic and short-duration, Circum-Arctic glacier surges, deposited during stadials. In contradistinction, the MIS 14 to MIS 10 interval have experienced a thick ice-cover (perennial ice or ice shelf) during long periods, including MIS 11 and possibly MIS 13. These interglacials depict relatively a low summer season insolation in contrast with that of other interglacials. Another feature merging from this revision is the shortness of the intervals with seasonally open sea-ice conditions. Often recorded by a few cm-thick sedimentary layers, these intervals are in phase with the mean summer season insolation (not the June solstice peak) and may have lasted a few ka at most, based on the example of the Holocene. Feedbacks from the Arctic Ocean towards climate/ocean conditions at lower latitudes include i) the effect of its sea-ice on albedo and latitudinal pressure gradients, and ii) the impact of its freshwater export on the Atlantic Meridional Overturning Circulation (AMOC). Due to its specific response to insolation and sea-level changes, the Arctic Ocean may have thus triggered out of phase climate and AMOC fluctuations during interglacials at lower latitudes, but it has globally remained a sediment-starved glacial ocean throughout most of the Brunhes epoch.

How to cite: Hillaire-Marcel, C., de Vernal, A., and Crucifix, M.: The revised Quaternary climatostratigraphy of the Arctic Ocean: linkages with insolation and sea-level changes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-619, https://doi.org/10.5194/egusphere-egu22-619, 2022.

15:17–15:23
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EGU22-219
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ECS
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Virtual presentation
Ellie Broadman et al.

Arctic Alaska lies at a climatological crossroads between the Arctic and North Pacific Oceans. The modern hydroclimate of the region is responding to rapidly diminishing sea ice driven in part by changes in heat flux from the North Pacific. Paleoclimate reconstructions have improved our knowledge of Alaska’s hydroclimate, but no studies have examined Holocene sea ice, moisture, and ocean-atmosphere circulation in Arctic Alaska, limiting our understanding of the relationship between these phenomena in the past. We present a sedimentary diatom assemblage and diatom isotope dataset from Schrader Pond, located ~80 km from the Arctic Ocean. We interpret these new datasets alongside synthesized regional records of Holocene hydroclimate, and sea ice reduction scenarios modeled by HadCM3. The paleo data synthesis and model simulations suggest the early and middle Holocene in Arctic Alaska were characterized by less sea ice, a greater contribution of isotopically-heavy Arctic-derived moisture, and wetter climate. In the late Holocene, sea ice expanded and regional climate became drier. This climatic transition is coincident with a documented shift in North Pacific circulation involving the Aleutian Low (AL) at ~4 ka, suggesting a Holocene teleconnection between the North Pacific and Arctic. The HadCM3 simulations reveal that reduced sea ice leads to a strengthened AL shifted west, potentially increasing transport of warm North Pacific water to the Arctic through the Bering Strait. Our findings demonstrate the interconnectedness of the Arctic and North Pacific on multi-millennial timescales and are consistent with future projections of less sea ice and more precipitation in Arctic Alaska.

How to cite: Broadman, E., Kaufman, D., Henderson, A., Malmierca-Vallet, I., Leng, M., and Lacey, J.: Coupled impacts of sea ice variability and North Pacific atmospheric circulation on Holocene hydroclimate in Arctic Alaska, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-219, https://doi.org/10.5194/egusphere-egu22-219, 2022.

15:23–15:29
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EGU22-2057
Anne de Vernal et al.

The shallow (~ 50 m deep) Bering Strait, which is the unique gateway linking the Pacific Ocean to the Arctic Ocean, deserves special attention as sea-level changes modify considerably the exchanges between the two oceans. Under high sea level, poleward heat transfer and freshwater fluxes from the Pacific impact the Arctic freshwater budget and sea ice distribution. Furthermore, sea level determines the status of the Arctic shelves, submerged or not, which plays a role in sea-ice production, as well as in the latent heat from Atlantic waters flowing northward through Fram Strait and the Barents Sea. Hence, high sea levels result in the connection of the Arctic basin with the Pacific, which modifies the Arctic freshwater and heat budgets and leads to the submergence of shelves, thus the potential development of sea-ice factories. The impacts of sea-level on the Arctic Ocean and subarctic seas are not easily reconstructed from sedimentary records, but radiocarbon-based chronologies and proxy-data covering the present interglacial provide useful information. For example, micropaleontological and geochemical records from the Chukchi Sea show progressive warming in surface water accompanying the increase of Pacific flux during the Holocene, until sea-level reached its present-day limit at ~ 4 ka BP. This contrasts with a trend towards perennial sea-ice cover in the southeastern Arctic and with changes at the eastern gateway of the Fram Strait, where cooling is recorded from early to late Holocene. Hence, we hypothesize that increased freshwater inflow from the Pacific into the Arctic together with enhanced sea-ice formation rates, both linked to sea-level rise, may have played a role in the general cooling trend culminating during the late Holocene.

How to cite: de Vernal, A., Hillaire-Marcel, C., Song, T., Liu, Y., and Falardeau, J.: Sea level and the Bering Strait gateway as determinant parameters in the ocean dynamics as illustrated from pan-Arctic Holocene records, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2057, https://doi.org/10.5194/egusphere-egu22-2057, 2022.

15:29–15:35
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EGU22-8403
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ECS
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Virtual presentation
Emmanuel Okuma et al.

The Lancaster Sound is currently one of the pathways for Arctic water and ice entering Baffin Bay. However, this gateway was blocked by the coalescing Laurentide and Innuitian Ice Sheets during the Last Glacial Maximum and only opened during the early Holocene after the various ice sheets had retreated (Dyke et al., 2002; Dalton et al., 2020). Core GeoB22336-4 is a well radiocarbon-dated sediment record from the Lancaster Sound Trough Mouth. Sedimentological and geochemical (elemental and mineralogical) properties of this core revealed four major units: (i) the deglacial unit (~14.5 – 9.7 ka BP) with a dense, foraminifera-free, gravel-rich diamict (>14.0 ka BP) that captures proximal ice-margin conditions, probably deposited under an extended thick ice-shelf environment, overlain by rapidly deposited gravel-bearing sandy-silty mud with intercalated turbidite layers reflecting strong input of ice-rafted material and mass wasting, likely resulting from the fast landward retreat of bordering ice sheets in response to regional warming; (ii) the early Holocene unit (~9.7 – 8 ka BP) characterized by a drop in sedimentation rate and the absence of ice-rafted material and reduction in detrital carbonates, suggesting a switch from tide-water to predominately land-terminating glaciers during glacial retreat; (iii) the unit deposited contemporaneously with the regional Holocene Optimum (~8 – 5.9 ka BP; Ledu et al., 2010; Jennings et al., 2011; St-Onge & St-Onge 2014) consists of rapidly deposited rather fine-grained sediments (up to 52 cm ka-1) possibly related to enhanced meltwater- and/or sea-ice-driven sediment input; and (iv) the neoglacial unit (<5.9 ka BP) with reduced sedimentation rates, a sediment provenance switch from calcite-dominated to dolomite-dominated detrital carbonates, and an increased organic matter flux to the seafloor, which led to a four-fold increase in bioturbation. This diverse sedimentary record reflects the complex ice-ocean-atmosphere interactions controlling the sedimentary dynamics and sediment provenance in northwestern Baffin Bay from the last deglaciation through the Holocene. It sheds light on the complex interaction between sediments delivered by local meltwater sources, mass wasting, iceberg and sea ice-rafting, the opening of the Arctic gateways through Lancaster Sound and Nares Strait, and the influence of warm Atlantic Water (AW). In addition, the Arctic Oscillation (AO) possibly governs surface waters and primary production in northern Baffin Bay including the development and extension of the North Water Polynya (NOW).

How to cite: Okuma, E., Titschack, J., Weiser, J., Kienast, M., Vogt, C., and Hebbeln, D.: Deglacial to Holocene changes in sediment characteristics and provenance in core GeoB22336-4 from Lancaster Sound Trough Mouth: Implications for environmental conditions in northwestern Baffin Bay, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8403, https://doi.org/10.5194/egusphere-egu22-8403, 2022.

15:35–15:41
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EGU22-11174
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ECS
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On-site presentation
Johanna Hingst et al.

The retreat of the Laurentide and Innuitian Ice Sheets in the Canadian Arctic Archipelago (CAA) during the late Quaternary led to the opening of Arctic gateways and the inflow of low salinity Arctic waters into Baffin Bay. Studies on marine sediments focusing on the timing and deglaciation pattern of Canadian Archipelago straits mainly concentrated on the Holocene. Here we present two marine radiogenic isotope records from the mouth of Lancaster Sound (GeoB22336-4) and from Barrow Strait (PS72/287) that cover the last ~14.5 ka BP, thus encompass the earlier deglaciation stage. The radiogenic isotope composition (Nd, Sr, Pb) of the detrital sediment fraction serves as provenance tracer and provides information on changing position of the ice margin and oceanographic conditions. Data from both sediment cores show contributions from highly variable source areas during deglaciation in response to the dynamics of the glacier termini involved. However, a strong influence of detrital carbonates, likely eroded from carbonate outcrops of the CAA and northern Baffin Island, by retreating ice, constitutes a dominant feature. Later, the post-glacial deposits recorded more uniform radiogenic isotope signatures until the mid/late Holocene transition, indicating relatively stable environmental conditions. In addition to local sources, isotope compositions in Lancaster Sound illustrate an increasing influence of sediments from Barrow Strait and thus the setting of oceanographic conditions enabling sediment transport from the central CAA towards the NW Baffin Bay. According to these observations and based on a preliminary age model, complete deglaciation with subsequent flushing of major channels is assumed to have occurred at approximately 10 ka BP. During the late Holocene, slightly changing Sr, Pb, and Nd isotope signatures in both cores probably indicate renewed regional ice advances in response to the neoglacial cooling.

How to cite: Hingst, J., Hillaire-Marcel, C., Lucassen, F., Okuma, E., and Kasemann, S.: Late Quaternary deglaciation pattern of Lancaster Sound and Barrow Strait traced by radiogenic isotope records in marine sediments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11174, https://doi.org/10.5194/egusphere-egu22-11174, 2022.

15:41–15:47
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EGU22-4935
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ECS
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On-site presentation
Defang You et al.

The last glacial termination is an unstable transition state characterized by abrupt climate changes, while the related physical mechanisms are still not fully understood. Here, we present well-dated high-resolution sedimentary records from the eastern Labrador Sea representing the last 23 ka. Based on our biomarker records, there was seasonal to permanent sea ice cover before 11.7 ka BP. During 11.7 to 8.2 ka BP, ice-free conditions were interrupted by several sea ice expansions, while no sea ice after 8.2 ka BP. Besides Heinrich Event 1, four prominent cold events have been identified during 14 ka to 8.2 ka BP. These abrupt events are marked by increases in sea ice, decreases in sea surface temperature, and weak deep current intensity. We propose that these events were mainly triggered by collapses of the Laurentide Ice Sheet and/or Greenland Ice Sheet, resulting in icebergs/meltwater in pulses into the Labrador Sea. This caused surface freshening, which potentially promoted the stratification of surface water, prevented the northward inflow of Atlantic Water, and limited deep water production in the Nordic Seas, consequently disrupting the climate.

How to cite: You, D., Stein, R., and Fahl, K.: Abrupt climate changes caused by meltwater pulses in the Labrador Sea during the last glacial termination, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4935, https://doi.org/10.5194/egusphere-egu22-4935, 2022.

15:47–15:53
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EGU22-5289
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ECS
Joanna Davies et al.

It is unequivocal that the climate is changing; marine terminating glaciers in Northeast Greenland (NEG) have experienced rapid speedup and retreat in recent decades as a result. The Zachariae Isstrøm (ZI) began accelerating in 2000, resulting in the total collapse of its floating ice tongue. This has been partly attributed to basal melting caused by the warming of Atlantic Water (AW). Unfortunately, our understanding of the interaction between these entities is somewhat limited by the length of instrumental records. Examining proxies preserved in marine sediment cores provides an alternative method to understand these changes on longer timescales.

Here we apply a multi-proxy approach (XRF, benthic foraminifera, stable isotopes, grain size, CT scans) to marine sediment core DA17-NG-ST08-092G, collected from the NEG continental shelf, 90km east of the ZI terminus. Our results indicate that the site was free of grounded ice at least as early as 12.5 ka cal BP, and most likely before 13.4 ka cal BP. The inflow of AW onto the continental shelf may have played a role in the seemingly early deglaciation at this site. Between 13.4 and 11.2 ka cal BP the site was overlain by a floating ice tongue, most likely the ZI, with AW and PW flowing beneath. Following this, the ZI briefly retreated westwards (11.2-10.8 ka cal BP) before it re-advanced (10.8-9.6 ka cal BP); there was a strong influx of AW throughout these periods. Between 9.6 and 7.9 ka cal BP the ZI retreated westwards again, before a drastic shift in ocean circulation occurred at 7.9 ka cal BP. At this time, there was a sharp decline in AW corresponding to an increase in PW flowing beneath perennial sea ice. In the final part of the record, AW returns and there was likely a breakup of the perennial sea ice.

How to cite: Davies, J., Møller Mathiasen, A., Kristiansen, K., Elnegaard Hansen, K., Wacker, L., Kristian Olsen Alstrup, A., Lajord Munk, O., Pearce, C., and Seidenkrantz, M.-S.: Linkages between ocean circulation and the Zachariae Isstrøm in the Early Holocene, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5289, https://doi.org/10.5194/egusphere-egu22-5289, 2022.

15:53–15:59
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EGU22-9431
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ECS
Tuomas Junna et al.

The NE Greenland shelf, together with the Fram Strait, form the main sea ice and cold-water transport pathway between the Arctic Ocean and the Nordic seas. As such, these regions play a part in the Atlantic meridional overturning cell that is driven by the thermohaline convection taking place in subpolar and Polar regions. The ocean circulation, freshwater export and sea ice extent are heavily influenced by the interplay of oceanography, climate, glacial landforms and bathymetry.

Over the outer NE Greenland shelf, a layer of low salinity, cold Polar Water overlies a body of Atlantic Water (AW) that is either recirculated directly across the Fram Strait or further in the Arctic Ocean from where it returns as colder, modified Arctic-Atlantic Water. The relative contributions of these two types of AW recirculation bear significant implications to the deep-water formation and thus, the global ocean circulation, but little is known about the change in AW source over time and how it affects the local environmental settings.

This study aims to describe the paleoceanographic development of the outer Norske Trough using a multi-proxy approach to sediment gravity core DA17-NG-ST12-135G.  The core was taken on the NorthGreen17 Expedition from the outmost location in an east-west transect of cores along the trough. When combined with the other cores, it can be used to reconstruct the  oceanic forcing on the northeastern Greenland Ice Sheet  and its deglaciation history along the Norske Trough. The data used includes AMS 14C dating, sedimentary description, grain size analysis, µ-XRF core scanning and benthic foraminifera analysis. The preliminary results suggest intermittent early AW water influence and high seasonal productivity just east of the Northeast Greenland Ice Stream grounding line during the early deglaciation. AW influence on the outer NE Greenland Shelf is relatively constant after the deglaciation, but changes in productivity and current strengths are captured by the data.

How to cite: Junna, T., Pearce, C., Hansen, K., Davies, J., Quirós, A., and Seidenkrantz, M.-S.: Late Glacial paleoceanography in the outer Norske Trough, NE Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9431, https://doi.org/10.5194/egusphere-egu22-9431, 2022.

15:59–16:05
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EGU22-4347
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ECS
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Virtual presentation
Adrián López-Quirós et al.

The Greenland Ice Sheet (GIS), the second largest ice sheet on Earth, has experienced a dramatic ice mass reduction during the last decades, coincident with global warming and an increase in atmospheric CO2. About 16% of the GIS is currently drained via marine terminating glaciers, mostly through the Northeast Greenland Ice Stream (NEGIS; with ~12%). Two cross-shelf troughs (Norske and Westwind troughs) served as drainage pathways of the NEGIS. According to numerical ice-sheet models, a whole meltdown of the GIS may cause a global sea−level rise of >7 m, causing permanent damage to the environment and countless economic impacts on our coastal society. In order to better understand the processes driving these present changes, studies of the development of glaciers/glacial troughs and ice sheets in response to past climate changes are required for testing numerical models that seek to predict ice-sheet response to anthropogenic climate change.

In this study, high-resolution INNOMAR sediment subbottom profiler data combined to multi-proxy analyses of gravity core DA17-NG-ST10-117G, obtained from Norske Trough during the NorthGreen17 expedition, are investigated. Multi-proxy data derived from the sediment gravity core include 14C-derived ages, descriptions of sedimentary units, compositional variability of ice-rafted debris, and continuous logging of magnetic susceptibility and micro-XRF core scanning. In Norske Trough, submarine glacial landforms indicate that ice sheet retreat to the outer middle shelf after the Last Glacial Maximum (LGM) was stepwise, with phases of grounding line stabilization, while ice sheet retreat from the middle shelf to the coastline during deglaciation was fast. Sedimentological evidence at our recorded coring site captures the transition from sub–ice stream (subglacial) environments to proximal (proglacial)/distal glaciomarine conditions during the LGM to Holocene recession. In addition, preliminary foraminifera analysis indicates warmer recirculating Atlantic Water on the middle Norske Trough immediately on deglaciation, suggesting that oceanic forcing very likely played a significant role during the retreat of the ice margin. This presentation will include a comprehensive comparison of the spatio-temporal sedimentation patterns across the Norske Trough.

How to cite: López-Quirós, A., Andresen, K. J., Davies, J., Junna, T., Nielsen, T., Pearce, C., and Seidenkrantz, M.-S.: Retreat of the Northeast Greenland ice stream during the last glacial termination - a case study from Norske Trough, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4347, https://doi.org/10.5194/egusphere-egu22-4347, 2022.

16:05–16:11
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EGU22-11646
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ECS
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On-site presentation
Rebecca McPherson et al.

During the last two decades, rising ocean temperatures have significantly contributed to accelerated mass loss of the Greenland Ice Sheet. The melting of the ice sheet is now the single largest contributor to global mean sea level rise. Warming subsurface Atlantic Intermediate Water (AIW) found on the wide continental shelf of Northeast Greenland and in the fjords interacts with marine-terminating glaciers, which until recently were considered stable, and causes their rapid melting and retreat. The main source of these waters is the westward recirculation of subducted Atlantic Water (AW) in Fram Strait, which has shown a warming of up to 1°C over the past few decades.

The variability of the AIW on the Northeast Greenland (NEG) shelf is investigated using historical hydrographic observations and high-resolution numerical simulations with the Finite-Element-Sea ice-Model (FESOM2). There is excellent agreement of both the mean and long-term distribution of AIW on the shelf between the model and observations. The two main circulation regimes of AW in Fram Strait are also well-replicated by the numerical simulations.

The dominant variability of the AIW temperature occurs at interannual timescales. A shelf-wide process drives this variability of AIW temperatures. EOF analysis shows that over 81% of the variance of maximum AIW temperatures is explained by the first mode, which features a monopol-like pattern across the whole NEG shelf. There is a strong co-variability between the maximum AIW temperature and the volume transport of AIW towards the glaciers, which moves through the deep trough system as a bottom intensified jet and recirculates on the shelf. A connection between the AIW temperatures on the shelf and the AW boundary current along the shelf edge suggests the East Greenland Current influences AIW properties. An increase in strength of the current corresponds to greater AIW volume transport through the trough system, and also warmer AIW and AW temperatures on both the shelf and off the continental slope. This suggests that the drivers of variability of AIW temperatures on the NEG shelf may be found further offshore, with a connection to AW circulation in Fram Strait.

How to cite: McPherson, R., Wekerle, C., and Kanzow, T.: Variability of Atlantic Water on shelf of Northeast Greenland: Patterns and Drivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11646, https://doi.org/10.5194/egusphere-egu22-11646, 2022.

16:11–16:17
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EGU22-8979
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ECS
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On-site presentation
Simin Gao et al.

Source-specific highly branched isoprenoids (HBIs) have been recently served as a binary or semi-quantitative biomarker to indicate the sea ice extent in the past. Since the light intensity controlled by overlying snow cover and sea ice thickness has a significant impact on the productivity of photoautotrophic organisms and environmental water is the sole source of the hydrogen for the biosynthesis of these organisms, the hydrogen isotope ratio (2H/1H) of HBIs holds the potential to reveal more characteristics of sea ice. In this study, based on the observation of natural settings underneath sea ice, diatom Pleurosigma intermedium were grown at irradiances from 20 to 300 μmol m-2 s-1 in laboratory conditions and harvested from exponential phase and stationary phase respectively to investigate the effect of light and growth phase on hydrogen isotope fractionation in HBIs. Gas chromatography-mass spectrometry (GC-MS) screening showed that a triene (C25:3) and a tetraene (C25:4) C25 HBI alkene were detected in all samples from varying irradiances. A remarkable decline of the ratio of C25:3/C25:4 from higher to lower irradiances was observed. However, there was no significant change in the concentration of C14 (myristic), C16:1 (palmitoleic) and C16 (palmitic) fatty acids with varying light intensity. In addition, terpenoids such as phytol, squalene and range of sterols were also be identified. Published studies on phytol, fatty acid and sterol from Thalassiosira pseudonana and alkenones from Emiliania huxleyi have shown dramatic changes in hydrogen isotope fractionation and concluded that the source of nicotinamide adenine dinucleotide phosphate (NADPH) and the operation of acetogenic pathway, plastidic methylerythritol phosphate (MEP) and/or cytosolic mevalonic acid (MVA) of lipids are the key factors controlling 2H/1H fractionation. The integration of molecular distribution of HBIs, fatty acids and terpenoids in Pleurosigma intermedium together with our ongoing work on their 2H/1H and 13C/12C compositions will lead to a better understanding of diatom metabolism and biochemistry under different light conditions. This knowledge will be instrumental to a more robust interpretation of stable isotope data from environmental samples and thus will contribute to further developing HBI biomarkers as a tool for estimating not only the absence/presence of sea ice but also the ice type, thickness, and snow cover.

How to cite: Gao, S., Zhao, Y., Zhou, Y., Smik, L., Belt, S., Mock, T., and Pedentchouk, N.: The effect of irradiance on lipids of highly branched isoprenoids (HBIs) producing diatom culture of Pleurosigma intermedium: towards stable isotope proxies for the paleo sea-ice reconstructions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8979, https://doi.org/10.5194/egusphere-egu22-8979, 2022.

16:17–16:23
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EGU22-1648
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Highlight
Nanna Bjørnholt Karlsson et al.

The Greenland ice sheet outputs freshwater into the Greenlandic fjords in the form of icebergs and liquid meltwater. This freshwater flux affects the fjords’ water circulation and ecosystems. In recent decades, the mass loss from the ice sheet has increased causing an increasing volume of liquid and solid freshwater to enter the fjords and ocean around Greenland. The total volume of freshwater is currently challenging to determine on a fjord-basin scale due to disparate products that are difficult to compare and combine into a cohesive product. This entails that the effect of the glacially derived freshwater on fjord circulation and ecosystem is not well constrained.

Here, we present a new glacier-basin scale product that combines three existing products into a shared temporal and spatial framework. We use publicly available datasets of solid ice discharge (icebergs), surface meltwater run-off, and basal melt to present a cohesive overview of the influx of freshwater to the Greenlandic fjords. We then quantify the different dominant term for each glacier. The dataset will be freely available and will be of use to, for example, oceanographic and marine biological research activities.

This work was supported by PROMICE (Programme for Monitoring the Greenland Ice Sheet, GEUS) and ESA Polar+ 4D Greenland.

How to cite: Karlsson, N. B., Mankoff, K. D., Solgaard, A. M., Larsen, S. H., Fausto, R. S., and Sørensen, L. S.: Monthly-resolved Freshwater Flux from the Greenland Ice Sheet on a Glacier-Basin Scale, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1648, https://doi.org/10.5194/egusphere-egu22-1648, 2022.

16:23–16:29
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EGU22-8791
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ECS
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Virtual presentation
Ben Kopec et al.

As the Arctic warms, one of the fundamental changes has been the freshening of Arctic ocean waters, impacting ocean circulation and marine ecosystems, among many other critical changes. This increase in freshwater is largely the result of increased precipitation and runoff as part of an amplified Arctic water cycle and increased influx of glacial meltwater from around the Arctic, particularly from the Greenland Ice Sheet. Tracing the sources and extent of this freshwater is critical to understanding future changes to the Arctic seas. One way of delineating these water masses is through measuring its isotopic composition (δ18O and δD), where the freshwater varies significantly from older and other ocean water sources.

In order to identify these freshwater influxes, we conducted in-situ measurements aboard the USCGC Healy that transited the Chukchi and Beaufort Seas, the Northwest Passage, and performed numerous transects across Baffin Bay and the Labrador Sea, including detailed examinations of several key fjords and coastal regions of Greenland, during autumn of 2021. Over the length of this 45 day expedition, we continuously measured the isotopic composition (δ18O and δD) of surface seawater allowing us to fingerprint these sources of freshwater and assess the spatial extent of their influence. We also collected discrete samples from over 100 CTD casts, primarily in Baffin Bay, to identify how freshwater is distributed in the ocean water column. Through these measurements, we identified numerous freshwater influxes, including anomalously high proportions of freshwater in sections of the Beaufort Sea north of Alaska and in Uummannaq Fjord along the west Greenland coast. These isotopic measurements also allow for the disentangling of different freshwater sources (i.e., precipitation or glacial meltwater). Additionally, we find that the freshwater pulses along the west coast of Greenland corresponded with relatively high levels of chlorophyll and fluorescence, suggesting a possible link between this increase in biologic productivity and an increase in the proportion of freshwater.

How to cite: Kopec, B., Klein, E., Pedron, S., Bailey, H., Causey, D., Hubbard, A., Marttila, H., Noor, K., and Welker, J.: Seawater isotopic measurements (δ18O and δD) reveal significant freshwater influxes into the Arctic seas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8791, https://doi.org/10.5194/egusphere-egu22-8791, 2022.

16:29–16:35
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EGU22-9645
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On-site presentation
Fabrice Jégou et al.

Climate warming with permafrost thaw will modify lateral carbon export, from terrestrial to aquatic ecosystems with a potential huge impact on the Arctic rivers, draining organic-rich soils and in fine into the Arctic Ocean. The majority of annual DOC fluxes by Arctic rivers are transported during the snowmelt break-up period, which makes field measurements of DOC difficult. Passive spatial remote sensing is a very relevant tool to increase the spatial and temporal coverage of these observed values.

In the framework of the French CNES DOC-Rivers project we proposed to apply the approach consisting in analyzing satellite imageries to evaluate DOC concentrations in the 6 great Arctic Rivers: Lena, Ob’, Yenisey, Yukon, MacKenzie, Kolyma. The algorithm, first, establishes a multi-linear relationship between ground-based chromatic dissolved organic matter (CDOM) observations and specific satellite color bands to construct a complete satellite CDOM database. Another linear regression is used afterward with in-situ data from the Arctic Great Rivers Observatory (ArcticGRO) initiative to correlate CDOM and DOC observations. Using this second linear regression, we can predict the DOC content from the previous construct satellite CDOM database. River discharge measurements from the ArcticGRO database also enable to estimate the evolution of DOC export to the Arctic Ocean from satellite data.

We applied this approach to high-resolution satellite data issued from Sentinel 2 (A 2015-2022, B 2017-2022) and Landsat 8 (2013-2022) to create a multi-instrumental synergy. This new database provides an unprecedented source of information for understanding DOC dynamics of in Arctic rivers and assessing its transfer from large catchments to the Arctic Ocean. This database provides information on the variability of DOC during the whole ice-free season and serve to locate areas with higher concentrations and fluxes during the 2013-2021 period. We plan to complement our database on future period with data from new satellite missions (Landsat 9, Sentinel 2C), on the present time with data from on-going missions (Sentinel 3, MODIS) and on past period with data from low resolution observations as Landsat 5 and Landsat 7. This extension of the database over a longer period of time will furnish insight in response to climate warming.

How to cite: Jégou, F., Jallais, G., Salmon, E., Guenet, B., Herrault, P.-A., Gogo, S., Gandois, L., Guimbaud, C., Laggoun-Defarge, F., Moulard, N., Teisserenc, R., and Moquet, J.-S.: Variability of dissolved organic carbon (DOC) in the 6 largest Arctic rivers estimated using high resolution Sentinel-2 and Landsat-8 imageries over the 2013-2021 period., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9645, https://doi.org/10.5194/egusphere-egu22-9645, 2022.

16:35–16:40
Discussion

Thu, 26 May, 17:00–18:30

Chairpersons: Anne de Vernal, Michal Kucera, Henrieka Detlef

17:00–17:06
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EGU22-300
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ECS
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Virtual presentation
Anastasiia Zemlianskova et al.

Significant changes are observed in the water exchange system of the North-Eastern Eurasia which still is the remote and poorly studied region of the cryosphere. Aufeis which are well recognized from the space may serve as the indicators of such changes. Aufeis are the ice sheets formed in permafrost environment due to the layer-by-layer freezing of discharged underground or surface water, their size may reach tenths of square kilometers. The primary goal of this study is to assess the changes in the dynamics of the characteristics (area and volume) of the giant Anmangynda aufeis based on historical and modern observational data. It is located in the zone of mountainous continuous permafrost of the Magadan region of Russia and was extensively studied in 1962-1992.

We combined and analyzed the data of historical materials (1962-1992) with recent data from Landsat and Sentinel images (2000-2020) and our own ground-based observations on the perennial and annual dynamics of aufeis area (2020-2021). Aufeis volume was measured in 1962-1992 and in 2020-2021, but for the period of 2000-2019 the values were estimated based on the regional formula developed by [Sokolov, Sarkysyan, 1981].

Maximum area of aufeis reached 6.6 km2 (about 1.6% of the basin area) in 1967. According to the data of 1969 its volume may grow up to 15.7 million m3. The greatest amplitude of fluctuations in the size of the aufeis (up to 30% of the average long-term value) was observed in the period up to 1976, then it did not exceed 10-15%. The smallest sizes of aufeis were 4.1 km2 and 5.3 million m3 in 1974, 4.3 km2 and 6.4 million m3 in 1990. Thus, over the thirty-year period of observations, the volume of aufeis has halved.

In the recent period, according to satellite data, these values reached the maximum of 5.8 km2 and 12.4 million m3 (2002). The lowest values were 2 times lower than the historical ones (1.9 km2 and 3.6 million m3, 2014). Now, to study the dynamics of aufeis area and volume, the authors have been using UAV shooting. The thickness of the ice is determined by measuring the height of the surface at different periods of the aufeis development. In 2021, the maximum ice thickness reached 4.4 m, and the historical maximum was 8 m.

The intra-annual dynamics of aufeis has also changed. Now the aufeis gets melted completely by August-September, and in the earlier periods the part of the ice sheet (about 4% of its maximum area) remained and was included in the formation of aufeis for the next year.

According to natural and climatic conditions, the river basin in which the Anmangynda aufeis is formed is representative for the mountainous landscapes of the North-Eastern Eurasia. Comprehensive interdisciplinary observations at this site are important to characterize the impact of climate change on natural processes in this region.

The study was carried out with the support of RFBR (19-55-80028, 20-05-00666), Russian Geographical Society (project 07/2021-I (continue)) and St. Petersburg State University (project 75295776).

How to cite: Zemlianskova, A., Alexeev, V., Makarieva, O., Nesterova, N., Shikhov, A., and Ostashov, A.: Temporal dynamics of the giant Anmangynda aufeis characteristics in changing climate, 1962-2021 (North-Eastern Eurasia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-300, https://doi.org/10.5194/egusphere-egu22-300, 2022.

17:06–17:12
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EGU22-10999
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ECS
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Virtual presentation
Ji-Eun Kim et al.

A merged biomass burning aerosol (BBA) emission dataset of satellite observations with fire proxies and fire models has been used in the Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations. Although this utilizes best estimates of fire emissions based on available observations, it results in inconsistency in interannual variability of BBA forcing in CMIP6 between the period of satellite-based fire emissions (1997-2014) and the periods before and after. Using the Community Earth System Model version 2 Large Ensemble (CESM2-LE) simulations, we identify rectified multiyear mean climate responses to interannually varying BBA emissions. The comparison of 50 ensemble members forced by high BBA variability with 50 members by low BBA variability over a limited time domain provides a unique opportunity to identify a forced climate response to interannual fluctuations of fire emissions with high fidelity. While mean aerosol emissions are nearly conserved between the two sets of ensembles, there is detectable warming in northern high latitudes with regionally distinct seasonal changes in response to variable emissions. We find that the multiyear warming occurs in concert with a net loss of soil ice and moisture in addition to a loss of Arctic sea ice. Our results suggest that the magnitude of interannual variability of aerosol emissions can act as climate forcing over multiple years through nonlinear interactions with the cryosphere and soil processes.

How to cite: Kim, J.-E., Yamaguchi, R., Rodgers, K., Timmermann, A., Lee, S.-S., Stein, K., Danabasoglu, G., Lamarque, J.-F., Fasullo, J., Deser, C., Simpson, I., Rosenbloom, N., Edwards, J., Kay, J., and Steuker, M.: Rectified multiyear warming in high latitudes by interannually varying biomass burning emissions in CESM2 Large Ensemble simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10999, https://doi.org/10.5194/egusphere-egu22-10999, 2022.

17:12–17:18
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EGU22-3499
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ECS
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On-site presentation
Carolyne Pickler et al.

Since the end of the 20th century, Greenland has been the largest contributor to sea level rise.  As temperatures continue to increase, this tendency is projected to continue.  This has resulted in numerous studies which evaluate present and future conditions of the Greenland Ice Sheet, many of which use general circulation models (GCMs). The majority of these focus on sea level rise and/or surface mass balance. While some analyses of atmospheric processes have been undertaken, these have typically been over a larger scale (Arctic or Greenland).  This has led to a lack of regional studies of atmospheric processes and how they are represented in GCMs, particularly over northeast Greenland, an area of increased interest in both its glaciology and atmosphere.

To address this, 67 CMIP6 GCM realizations were subject to the Pickler and Mölg (2021) model selection procedure to determine the most suitable realization over northeast Greenland.  The historical simulation of these realizations were evaluated for: (i) their ability to capture the space-time climatic anomalies over 1979-2014 with respect to ERA5 reanalysis data and (ii) their ability to simulate the mean climatic state of northeast Greenland with respect to four automated weather stations over 2009-2020.  MPI-ESM1-2-HR r6i1p1f1 was found to rank highest and ACCESS-ESM1-5 r10i1p1f1 lowest.

The 67 realizations were then evaluated on their ability to capture two important processes influencing the region: the North Atlantic Oscillation (NAO) and the Greenland blocking (GBI).  All realizations were able to simulate the NAO during boreal winter, while all failed to capture the GBI during boreal summer.  Furthermore, the ability of the top and bottom ranked realizations to simulate precipitation, katabatic winds, sea ice, and warm-air events were examined. This analysis reveals key differences between the representation of regional climates within the GCMs, which highlights the need for a rigorous selection procedure prior to estimating future changes.

How to cite: Pickler, C., Turton, J., Mölg, T., and McCrystall, M.: The representation of atmospheric processes in northeast Greenland in CMIP6 models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3499, https://doi.org/10.5194/egusphere-egu22-3499, 2022.

17:18–17:24
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EGU22-6260
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ECS
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Virtual presentation
Thomas Ballinger et al.

The northwest Atlantic Arctic has been recently characterized by rapid environmental change. Examples in the last two-to-three decades include: accelerated retreat of eastern Canadian Arctic glaciers, melt over high-elevation and latitude areas of the Greenland Ice Sheet (GrIS), and shifts in Baffin Bay ice phenology. Many of these glaciological changes and associated extreme events are linked to atmospheric circulation anomalies over the North Atlantic and surrounding areas, including the frequent, intense, and/or persistent presence of Greenland blocking anticyclones. These mid-tropospheric (i.e., 500 hPa) high-pressure cells are often accompanied by invigorated temperature and moisture advection and cloud radiative processes that are known to provoke widespread melt of the region’s cryosphere, even during periods when melt tends to be uncommon. Blocking characteristics are often associated with melt processes, but how these processes and related air-sea exchanges feedback on this type of upper-level atmospheric pattern largely remain uncertain. Evaluating these processes and their uncertainties is especially relevant in the cold season, when upward surface fluxes persist along the ice edge and through thin sea ice cover. Such system-level interactions deserve attention for their multi-scalar effects on the local climate and cryosphere and impacts on the polar jet stream that influences North American and European weather regimes.

This study focuses on the autumn season (September-December) to evaluate interactions involving Baffin Bay’s ice cover and its turbulent and radiative fluxes, and regional atmospheric circulation and winds. Focus is directed on this season as net surface fluxes climatologically tend to intensify from one month to the next and have increased roughly in tandem with the strength and motion characteristics of the overlying circulation described by the Greenland Blocking Index (GBI), and Greenland Streamfunction Index (GSI), respectively. Using flux data from ERA5 reanalysis and the Atmospheric Infrared Sounder (AIRS), we utilize bi-and-multivariate techniques to examine how individual and collective surface flux terms relate to the autumn GBI/GSI variability and trends since 1979. We then take a process-scale view, and investigate such interactions between the Baffin Bay boundary conditions, associated surface fluxes, and the GBI/GSI patterns in months where extremes occur in the ice cover and GBI/GSI independently as well as in tandem for applicable cases. We further aim to model the interaction between autumn Baffin ice-ocean surface fluxes and upper-level patterns using CAM6 Prescribed SST AMIP Ensembles and wind-nudging CESM experiments to isolate the role of Baffin environmental change on the large-scale atmospheric circulation and vice versa.

How to cite: Ballinger, T., Topal, D., Ding, Q., Li, Z., Boisvert, L., Hanna, E., and Vihma, T.: Baffin Bay surface flux perspectives on autumn Greenland blocking, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6260, https://doi.org/10.5194/egusphere-egu22-6260, 2022.

17:24–17:30
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EGU22-7438
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Highlight
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Virtual presentation
Stephen Outten and Camille Li

Over a decade ago, researchers noticed that as the Arctic warmed rapidly, there was an apparent cooling over large areas of central Eurasia in the wintertime. Many theories were put forward suggesting that changes in wintertime sea-ice were linked to this observed cooling through some hereto unknown teleconnection. Numerous studies based on observations, reanalyses, and a vast array of modelling experiments have been undertaken to resolve this question. The ongoing debate regarding Arctic to mid-latitude teleconnections over the Eurasian sector has divided the scientific community, as highlighted by the work of Cohen et al. [2020], primarily between those in favour of sea-ice having a key role in giving rise to the cooling, and those who believe the cooling is primarily the result of internal atmospheric variability. While Eurasian cooling itself has mostly ended, the debate continues due to a desire to better understand the teleconnections underlying Northern Hemisphere climate variability.

Here we discuss a new synthesis study into Eurasian cooling, undertaken by an extensive team at the Bjerknes Centre over the past two years. The work breaks down the debate into a simple structure, examining first the findings of the observational-based studies and the modelling-based studies separately. In evaluating this body of literature, we attempt to avoid categorizing studies based on the researchers’ interpretations of their findings, and focus where possible on only the facts of what their analyses and simulations show. This has allowed us to reconcile some of the apparently conflicting results in the literature. To be clear, we do not present a new mechanistic understanding of the processes underlying Eurasian cooling. However, laying out the existing research in an objective and structured manner has allowed us to propose a new framework within which to view the problem, wherein we clarify the distinct roles of internal variability and an external (sea-ice driven) forcing of Eurasian cooling.

How to cite: Outten, S. and Li, C.: Eurasian wintertime cooling: New perspectives from an updated synthesis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7438, https://doi.org/10.5194/egusphere-egu22-7438, 2022.

17:30–17:36
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EGU22-5951
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Highlight
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On-site presentation
Aurel Perşoiu and Monica Ionita

Several recent cold winters in North America and Western Europe has drawn attention on the possible increase in the frequency and/or intensity of extreme events in the mid-latitude Northern Hemisphere. Whether these could result form a strengthening or weakening of the circumpolar vortex and/or shift in the position of the North Atlantic storm track is still a matter of hot debate. A less known player in this conundrum is the dynamics of the Siberian High, one of the major semi–permanent and quasi–stationary weather systems in the Northern Hemisphere; active in winter and associated with dense and cold air masses over Asia and East Europe. The causes behind the variability of the of the Siberian High (strengthening and south and westwards expansion) are still poorly understood, yet important in the context of future climatic changes expected in the core area of its manifestation. In this context, we present here an overview of the present and past (~5000 years) dynamics of the Siberian High, based on 1) modern climate data from Asia and Eastern Europe and 2) proxy-based reconstructions of winter climatic conditions (temperature and precipitation amount). Our analysis starts with a instrumental-based investigation of the mechanisms behind the onset, strengthening and westward expansion of the high-pressure cell centered over North Asia. We further construct and test several hypotheses behind these mechanisms and test them by analyzing the dynamics of winter conditions during several episodes of particularly cold events in the Northern hemisphere (at 4.2 ka BP, 2.8 ka BP, 1.3 ka BP, 0.8-0.2 ka BP). We tentatively suggest that high insolation gradients between summer and winter in the high–latitudes of the Northern Hemisphere could result in the weakening of the polar vortex and increase in the meandering behavior of the jet that leads to an early onset of winter in North Asia. The expanding snow cover reinforces the strength of the Siberian High, leading to its expansion towards south and west and thus bringing colder conditions in West Asia and Europe. Future Arctic amplification could result in a higher frequency of similar behavior of the climate system, thus leading to more frequent and stronger cold spells across Europe.

How to cite: Perşoiu, A. and Ionita, M.: The Beast from the East - winter atmospheric blocking over Eastern Europe during the Late Holocene and its role in regional climate variability, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5951, https://doi.org/10.5194/egusphere-egu22-5951, 2022.

17:36–17:42
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EGU22-5172
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On-site presentation
Olivia Linke et al.

The Arctic amplification is driven by several intertwined causes including the interplay of locally positive radiative feedbacks. The lapse-rate feedback (LRF) is a dominant driver of Arctic amplification and arises from the vertically non-uniform warming in the troposphere. In the Arctic, the LRF enforces a positive radiative feedback as the warming is most pronounced at the surface, but becomes smaller at higher altitudes which feedbacks positively on the initial greenhouse effect. This stands in contrast to the processes in the tropics, where a stronger warming of the upper troposphere dampens the greenhouse effect.

We investigate the nature of the Arctic LRF by using ERA5 Reanalyses and CMIP6 models to compute the feedback via simplified radiative transfer calculations (radiative kernels).

The Arctic LRF is unique in terms of its geographic distribution, seasonality and time evolution. From a global perspective, the LRF is most positive in Arctic winter, but shows the strongest seasonality as it becomes negative in summer over the sea ice covered ocean. Our trend analysis shows that the positive winter LRF increased strongly during the past 30 to 40 years. This increase during boreal winter mediates the annual response and accounts for all Arctic surface types which we define as sea ice, sea ice retreat, open ocean and land. A special focus lies on regions of retreating sea ice, where the positive LRF is strongest throughout the year.

Our results are embedded in previous studies on the changing Arctic atmospheric energy budget through CO2-driven climate change. They show strongly increasing surface heat fluxes over areas of retreating sea ice which is mostly compensated by a decrease in atmospheric transport convergence, both of which can shape the maximum of the high-latitude positive LRF.

We finally carry out an inter-model comparison of linear trends of the Arctic LRF during the past 30 years of historical CMIP6 simulations. This includes more than 50 models to determine the performance of each model by relating to reanalyses data.

How to cite: Linke, O., Quaas, J., and Smith, C.: The nature of the Arctic lapse-rate feedback: Spatial distribution, seasonality and trends in ERA5 and CMIP6 data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5172, https://doi.org/10.5194/egusphere-egu22-5172, 2022.

17:42–17:48
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EGU22-5982
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Virtual presentation
Peter Yu Feng Siew et al.

Arctic sea ice loss in recent decades has been proposed to influence atmospheric circulation at lower latitudes, producing feedbacks that amplify ice loss via thermodynamic and mechanical forcing. One proposed teleconnection pathway arises from autumn Barents-Kara sea ice reduction and leads to a negative North Atlantic Oscillation (NAO) in winter. The existence of such a pathway could improve predictions of  European weather on subseasonal to seasonal timescales. While autumn sea ice and the winter NAO are significantly correlated in satellite-era observations, this correlation appears to be absent in  coupled climate models, calling into question the underlying mechanism. By subsampling long simulations to create satellite-length records, we find a small number of samples across a range of CMIP5 and CMIP6 models that reproduce the observed correlation. In these samples, we observe similar circulation signals (e.g., weakening of the stratospheric polar vortex) as in the observations, but there is no evidence for a driving role from sea ice changes via turbulent heat fluxes. Rather than sea ice, blocking of the atmospheric circulation by the Ural mountains appears to be the key precursor to the winter NAO signal. Overall, our findings reconcile differences between observations and models in representing this Arctic-midlatitude teleconnection, and highlight the important role of atmospheric internal variability in Arctic change. 

How to cite: Siew, P. Y. F., Li, C., Ting, M., Sobolowski, S., Wu, Y., and Chen, X.: Atmospheric internal variability shapes the Arctic change and its feedback on local and remote circulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5982, https://doi.org/10.5194/egusphere-egu22-5982, 2022.

17:48–17:54
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EGU22-7950
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ECS
Sina Mehrdad et al.

The global warming has been observed to be more severe in the Arctic compared to the rest of the world. This enhanced warming i.e. Arctic Amplification is not just the result of local feedback processes in the Arctic. The stratospheric pathways of Arctic-midlatitude linkages and large-scale dynamical processes can contribute to the Arctic Amplification. The polar stratospheric dynamics crucially depends on the atmospheric waves at all scales. The winter polar vortex can be disturbed by gravity waves in the middle atmosphere. To investigate the sensitivity of the polar vortex dynamics, large-scale dynamical processes, and the stratospheric pathways of the Arctic-midlatitude linkages to the modification of gravity wave drag, we conduct sensitivity experiments using the global atmospheric model ICON-NWP (ICOsahedral Nonhydrostatic Model for Numerical Weather Prediction). These sensitivity experiments are performed by imposing a repeated annual cycle of the year 1985 for sea surface temperatures and sea ice as lower boundary conditions and for greenhouse gas concentrations as external forcing. This year is selected as both El-Nino Southern Oscillation and Pacific decadal oscillation were in their neutral phase and no explosive volcanic eruption has occurred. Hence, lower boundary and external forcing conditions in this year can serve as a useful proxy for the multi-year mean condition and an estimate of its internal variability. We performed simulations where in the control simulation the sub-grid parameterization scheme for both orographic and non-orographic gravity wave drags are switched on. The other two experiments are identical to the control simulation except that either orographic or non-orographic gravity wave drags are switched off.

    Recently, deep learning has extraordinarily progressed our ability to recognize complex patterns in big datasets. Deep neural networks have shown great capabilities to capture the dynamical process of the atmosphere. Applying deep learning algorithms on experiments’ results, the impact of gravity wave drag modifications on large-scale mechanisms of the Arctic Amplification will be analyzed. Special emphasis will be put on the effects of gravity wave drag modifications on the polar vortex dynamics.

How to cite: Mehrdad, S., Karami, K., Handorf, D., Quaas, J., Höschel, I., and Jacobi, C.: Sensitivity of stratospheric pathways of Arctic-midlatitude linkages to the modification of the gravity wave drag parameterization in ICON model using deep learning, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7950, https://doi.org/10.5194/egusphere-egu22-7950, 2022.

17:54–18:00
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EGU22-1637
Cryostratigraphy, chronology, and ground-ice stable isotopes of the Batagay megaslump in east Siberia indicate climate–permafrost interactions during the Middle and Late Pleistocene
(withdrawn)
Thomas Opel et al.
18:00–18:06
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EGU22-13183
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Virtual presentation
High-resolution record of environmental changes during Boreal (Eemian) transgression from the northeastern White Sea Region
(withdrawn)
Ekaterina Taldenkova et al.
18:06–18:12
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EGU22-11871
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ECS
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Highlight
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Virtual presentation
Arctic Amplification during the Last Glacial Inception due to a delayed response in sea ice and SST
(withdrawn)
Shan Xu et al.
18:12–18:18
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EGU22-11447
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Virtual presentation
Nuanced responses of seasonal sea ice to a warmer Arctic climate during the Holocene Thermal Maximum
(withdrawn)
Anna J. Pienkowski et al.
18:18–18:24
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EGU22-10913
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Virtual presentation
Observation of spatiotemporal variability of deep near-inertial waves in the western Arctic Ocean 
(withdrawn)
Jae-Hun Park et al.

18:24–18:30
Discussion and end session