Rising sea levels in the 21^st century threaten coastal communities with inundation, yet projecting the relative and global mean sea level response to climate warming is complex. Lack of contemporary analogues for future climate dynamics has turned attention to periods in the geologic past that can illuminate how Earth’s climate system reacts to temperature forcing. Recent evidence suggests the Antarctic and Greenland ice sheets may have retreated inland of their present-day extents during the mid-late Holocene (~8-3 ka), then readvanced until the pre-industrial. These findings have highlighted the utility of the mid-Holocene—when summer temperatures in the northern hemisphere may have neared 4 degrees hotter than preindustrial levels—as a partial analogue for future warming.

Here we present a new probabilistic estimate of mid-Holocene global mean sea level (GMSL). We construct an ensemble of global ice sheet reconstructions for the last 80 kyr that spans a range of possible mid-Holocene GMSL scenarios. We predict relative sea level from each model accounting for glacial isostatic adjustment and using a range of solid earth structures. We then compare these predictions to 10,733 postglacial sea-level indicators and weigh the GMSL curves from each ice model using data-model fits. The constraints placed on mid-Holocene global mean sea level clarify climate dynamics during this critical interval in Earth’s recent history, and enable new estimates of post-glacial Antarctic ice volume and the likelihood of mid-Holocene West Antarctic ice sheet readvance.

How to cite: Creel, R., Austermann, J., Kopp, R., Khan, N., Ashe, E., Kingslake, J., and Albrecht, T.: Probabilistic Estimation of mid-Holocene global mean sea level , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1953, https://doi.org/10.5194/egusphere-egu22-1953, 2022.

The beachrock formations represent a significant paleo-environmental proxy because they can record both the vertical and the horizontal evolution of the coastline. They have been used to assess Holocene coastline evolution and crustally induced relative sea level (RSL) change, notably in the Sea of Marmara. In this study, we report existence of the less known submerged beachrocks in the nearshore coastal area of Tekirdag city (Altinova), the northern Sea of Marmara. The beachrocks found in the Tekirdag coastline are locally spread, parallel to the coastline with an extend of about 5 km and at depths ranging from -2 to 0m below present sea level. The beachrock is defined by a calcite-cemented shoreline sandstone. The cement mineralogy and morphology of the beachrocks are indicative of the diagenetic environment, and therefore the examination of the cement characteristics and microstratigraphy can allow identify the type of cement and spatial relationship between the past shoreline and beachrock formation zone.

The Tekirdag coastal area is located in the western Marmara Region. The western coasts of the Marmara Region include a number of natural features inherited from their coastal evolution. Besides, relative sea level change during late Quaternary in this region and its vicinity are generally not homogeneous as a result of the tectonic activity controlled by the North Anatolian Fault Zone (NAFZ) which played a crucial role in the coastline evolution at different periods of the region.

The aim of our study to reconstruct the shoreline modification using beachrocks in the study area. For this purpose, we coupled a series of methodologies for the paleo-environmental and geomorphological study of the coastal zone and the shallow submarine area, which included: a) coring from submerged beachrocks, b) petrographic and microstratigraphic analyses of cementation, c) monitoring of underwater beachrocks and coastal zone by drone and e) dating the formation of beachrocks. Through our analyses we aim to better contribute the use of beachrocks as accurate proxies for the RSL variation in the study area.

How to cite: Tarı, U., Sunal, G., Özcan, O., and Yaltırak, C.: Submerged beachrock: A tool for reconstructing relative sea level change example from Tekirdag coastline, Sea of Marmara, Turkey, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5004, https://doi.org/10.5194/egusphere-egu22-5004, 2022.

Our team has previously built a ~7500 year tsunami history for the northern patch of the Sunda Megathrust. However, the paleo-tsunami history south of Aceh province and the 2004 rupture patch remains poorly understood. We conducted geological investigation to better define the boundaries of rupture patches along the Megathrust.

We utilized satellite imagery to pinpoint potential sites likely to archive evidence of paleo tsunami inundations and co-seismic land-level change. Due to the continuing Covid-19 pandemic and restrictions, our researchers from Singapore, and USA could not travel to Indonesia. However, because of the longstanding close collaboration between the Earth Observatory of Singapore and Syiah Kuala University, Banda Aceh, Indonesia, the project continued to progress. The Syiah Kuala University team investigated nearly 20 sites between Banda Aceh in the northern patch of the of Sumatra Megathrust and Padang in the south. Several sites preserved probable paleo-tsunami sediments. The paleo-tsunami sediments were identified from anomalous layers of sand in low energy environments where they would not normally occur, such as mangroves, coastal lowlands, and/or swales.

 
Here we present results of litho-, bio- and chronostratigraphical analysis from Susoh as well as preliminary information from sites along the coastline between Meulaboh and Padang. From Susoh we described stratigraphy from a series of cores to a depth of 4.75 m. The top 2.5 meters was dominated by muds typical of estuarine or tidal flat settings, but it is interrupted by three pulses of sandy muds. At 2.55 m we encountered a 0.2 m thick layer of course sand, underlain by a 0.5 m thick mangrove peat with a gradual transition into organic sandy muds and sands. Pollen analysis from the fine-grained organic layers indicate they were formed in a mangrove environment. Radiocarbon dating of the organic macrofossils from the mangrove peat indicate the tsunami event occurred post 1850 cal. yrs BP. Our research continues to improve our understanding of the Sumatran Megathrust.

How to cite: Majewski, J., Richards, G., Daly, P., Switzer, A., Ismail, N., Afrizal, T., Christie, M., and Horton, B.: Extending paleo-tsunami records south of the 2004 Indian Ocean Tsunami patch, Sumatra, Indonesia: 2022 update, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12629, https://doi.org/10.5194/egusphere-egu22-12629, 2022.

We present new proxy-based sea-level reconstructions for southern New Zealand spanning the last millennium. These palaeo sea-level records usefully complement sparse Southern Hemisphere proxy and tide-gauge sea-level datasets and, in combination with instrumental observations, can test hypotheses about the drivers of 20^th century global sea-level change, including land-based ice melt and regional sterodynamics. We develop sea-level transfer functions from regional datasets of salt-marsh foraminifera to establish a new proxy-based sea-level record at Mokomoko Inlet, at the southern tip of the South Island, and to improve the previously published sea-level reconstruction at Pounawea, located about 110 km to the east. Chronologies are based on radiocarbon, radiocaesium, stable lead isotope and pollen analyses. Both records are in good agreement and show sea level several decimetres below present over the last millennium, before a rapid sea-level rise in the first half of the 20^th century that reached maximum rates in the 1940s. Previously reported discrepancies between proxy-based sea-level records and tide-gauge records are partially reconciled by accounting for barystatic and sterodynamic components of regional sea-level rise. We conclude that the rapid sea-level rise during the middle 20^th century along the coast of southern New Zealand was primarily driven by regional thermal expansion and ocean dynamics.

How to cite: Garrett, E., Gehrels, R., Hayward, B., Newnham, R., Gehrels, M., Morey, C., and Dangendorf, S.: Late Holocene sea-level change in southern New Zealand , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5675, https://doi.org/10.5194/egusphere-egu22-5675, 2022.

Tillandsia landbeckii is a bromeliad that inhabits the hyperarid coast of the Atacama Desert where it survives solely on moisture and nutrients from fog. It does so by constituting a unique dune ecosystem that maximizes its fog capture potential as well as preserving layers of buried tillandsia plants. These buried layers can survive over multiple millennia and here we present data based on stratigraphic, radiocarbon, stable isotopes, and leaf wax analyses that we are applying to these ancient leaves and stems to reconstruct past variations in fog moisture and nutrient cycling. Some of the oldest buried layers date back to >10,000 14C yrs BP and our results show that both d15N and leaf waxes are capable of tracking variations in moisture changes although we observed significant variation in d15N values across living plants which may be due to the plants' age. Past variations in fog likely track variations in large-scale synoptic climate features such as the height of the Marine Boundary Layer and the strength of the Southern Pacific Anticyclone.

How to cite: Latorre, C., Contreras, S., Jaeschke, A., Garcia, J. L., and del Río, C.: Ancient Tillandsia landbeckii dune ecosystems and their potential to reveal past variations in coastal fog moisture during the Holocene in the Atacama Desert, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7988, https://doi.org/10.5194/egusphere-egu22-7988, 2022.

Proglacial sediments hold continuous and high-resolution records of past glacier dynamics. In this study, we examine the sediments of Eyre Fjord (Chilean Patagonia, 49°S), which is fed by Pio XI Glacier, to gain a better understanding of how the surging phase of a growing glacier is recorded in marine sediments. Pio XI Glacier has experienced a net advance of >10 km since 1945 and has had several surging phases that each last 2 – 3 years and occur every ~14 years. The last reported surging phases happened between 1976 – 1979, 1997 – 1998, and 2014 – 2018. Thirty CTD profiles taken in the fjord along one longitudinal and three transverse transects in February 2019 show that sediment transfer through the fjord during a quiescent (i.e., non-surging) phase in summer primarily happens by means of widespread (unchannelised) hyperpycnal flows that are 20 – 100 m thick. To assess spatiotemporal variability in sedimentation throughout the fjord, nine sediment cores were collected in 2019. Concentrations of short-lived radionuclides suggest a sedimentation rate of 3 – 20 cm/year. Sediment grain size and magnetic susceptibility, (CT) density, and inorganic geochemistry (Fe, Ti, K, Mn, Zr, Zn, Rb, Sr), which were obtained at higher resolution, were used as proxies for hydrodynamic conditions in the fjord. The longest sediment record holds fine glacial mud and low density sediments between 135 – 70 cm and in the upper 10 cm, which indicate relatively low hydrodynamic activity, likely corresponding to the quiescent phases before 2014 after 2018. Between 70 cm and 10 cm, the overall denser and coarser sediments intercalated with cm-thick sandy layers indicate higher hydrodynamic activity and flood events, most likely representing the most recent (2014 – 2018) surging phase of the glacier. Interestingly, the thickest and coarsest flood deposits seem to be concentrated at the top of the sediment unit that represents the surging phase suggesting that the floods are the most intense towards the end of the surging phase. Overall, these results show that quiescent and surging phases of surge-type glaciers leave distinct sedimentary signatures in fjord sediments, offering the possibility to use longer sediment records to identify former surging phases.

How to cite: Piret, L., Bertrand, S., and Moffat, C.: Fjord sedimentary signature of the last surging phase of Pio XI Glacier (Chilean Patagonia), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10055, https://doi.org/10.5194/egusphere-egu22-10055, 2022.

Climate Change has increased the intensity, duration, and frequency of extreme weather events such as heatwaves (HW), which have impacts on ecosystems, economics, and human populations, including adverse health effects and the increase in the number of deaths due to the heat stress. However, there are still few studies evaluating the occurrence of adverse health due to HW in South America. Particularly in Brazil, regional differences in the effects of heatwaves are expected due to their continental dimensions, which makes it necessary to carry out local studies. This work presents a long term analysis of the occurrence of HW in the 14 major metropolitan regions (MRs) in Brazil, namely: Manaus, Belém, Salvador, Recife, Fortaleza, Goiânia, Brasília, Cuiabá, São Paulo, Rio de Janeiro, Belo Horizonte, Porto Alegre, Curitiba and Florianópolis. Observational temperature data (1970-2020) provided by the National Institute of Meteorology (INMET) were used to compute the Extreme Heat Factor (EHF) index, which was used to identify and classify HW in terms of severity.  Significant and positive trends in the frequency of HW were observed over decades in all MRs, particularly in the north (Manaus and Belém) and central west region (Goiania and Brasilia). Particularly, from 2014 to 2019, all the MRs presented HW regime every year, including severe and/or extreme events. In general, the longest and the most intense HW in Brazilian MRs occurred in the last decade (2010-2020), with the exception of the 1997–1998 El Niño-related events. Daily mortality and hospital admission data from the Brazilian Public Health System (SUS) were used to assess the relationships between HW and health. Results indicate excess mortality (observed to expected ratio) during HW events in the MRs studied, with the elderly being the most vulnerable age group, in agreement with previous studies. The cause of death and the gender susceptibility to HW were also analyzed, and the results vary among the different MRs. This work provides an extensive characterization of the occurrence of HW in Brazil and valuable insights for the implementation of public mitigation and adaptation strategies in some of the most populated regions of South America.

This work was supported by FIOCRUZ [grant VPPCB-003-FIO-19] and FAPERJ [grant E26/202.714/2019]. D.M.S. was supported by FIOCRUZ [grant VPPCB-003-FIO-19].

How to cite: Monteiro dos Santos, D., N. Garcia, B., L. Geirinhas, J., Russo, A., F. Peres, L., and Libonati, R.: Long term characterization of heat waves in Brazil and their impacts on mortality rates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10721, https://doi.org/10.5194/egusphere-egu22-10721, 2022.

Thwaites Glacier (TG) is thinning and accelerating while sitting on a landward-dipping bed, with an ice shelf that is rapidly disintegrating and losing its ability to buttress ice flow from upstream, and is in deep water that allows warm Circumpolar Deep Water (CDW) to reach its grounding zone.  Significant retreat of TG would trigger loss of ice across the region.  In recent decades, the mass balance of TG has become increasingly negative, suggesting that unstable retreat may have already begun.  The Thwaites Offshore Research (THOR) group has just completed four field deployments aimed at understanding the recent history of TG and neighboring ice, including Pine Island Glacier (PIG).  Three cruises on the RVIB N.B. Palmer, combined with sub-ice-shelf sediment coring, provide a suite of new data along the TG and PIG margins.  Data include multibeam surveys, 3.5 kHz subbottom profiler, over 100 new sediment cores, and high-resolution seismic profiles.  Break-up of floating ice cover in front of TG in 2019 allowed surveying of previously unmapped seafloor.  Major calving of PIG in 2020 allowed marine surveying over the locations where sub-ice-shelf cores were collected in the past, allowing direct ties between ice-based and marine work.  As of this writing in January 2022, we are entering into the Amundsen Sea for our third marine field season. 

Sediment cores record the history of grounding-zone retreat and ice interaction with the ocean over timescales from decades to several thousand years.  Proxies used to reconstruct ice and ocean histories include sedimentary facies analysis, diatom and foraminiferal assemblage data, and geochemical analyses.  Sedimentological analyses show a diverse array of lithofacies attributed to different environmental conditions.  Many cores across the region contain laminated mud with sparse gravel and sand, suggesting deposition of meltwater deposits. Downcore ²¹⁰Pb measurements are used to create age models of the past ~100 years.  Combination of ages with facies models, including CT scans, reveals that the progressive detachment of Thwaites from pinning points began in the mid twentieth century, coincident with retreat of PIG (Smith et al., 2017) and with increasing advection of warm water onto the Amundsen shelf (Hillenbrand et al., 2017).  Conversely, Cranton Bay, to the northeast of PIG and separated from Pine Island Bay by a shallow sill, appears to be characterized by cold deep water and high productivity, allowing it to serve as an endmember different from the records obtained proximal to the large glacial outlets where CDW is impinging.

The satellite record of glacial retreat is inherently short.  Observations are accumulating about forcing mechanisms that can impact the stability of ice, such as increased CDW on the Amundsen Sea shelf.  However, without the time to observe the response of the ice, discovery of the forcing mechanisms is just half the story.  The other half of the story is completed by using the paleo record to see how ice has responded to drivers in the past.

How to cite: Wellner, J., Clark, R., Lehrmann, A., Lepp, A., Hillenbrand, C.-D., Totten, R., Simkins, L., Comas, M., Mawbey, E., Hopkins, R., Smith, J., Anderson, J., Hogan, K., Nitsche, F., Graham, A., and Larter, R.: Pre-satellite retreat of Thwaites and Pine Island glaciers: Recent results from sediment cores, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10609, https://doi.org/10.5194/egusphere-egu22-10609, 2022.

Antarctic ice-sheet instability is recorded by ice-rafted debris (IRD) in mid- to high-latitude marine sediment, especially throughout climate transitions. The middle Miocene climatic transition (MMCT), 14.2 to 13.8 Ma, which marks the end of a significant warm period during the mid-Miocene, saw a rapid cooling of ca. 6-7 °C in the high-latitude Southern Ocean. This climatic shift was also accompanied by a global δ¹⁸O excursion of ca. 1‰, indicating a time of global cooling and significant Antarctic ice expansion (Shevenell et al., 2004). The MMCT is recorded by numerous IRD-rich sediment horizons in deep-sea sediment cores around the Antarctic margin, reflecting iceberg calving during times of ice-sheet instability. Resolving the locations of iceberg calving sites by detrital provenance analysis during the MMCT is also an important tool for forecasting effects of anthropogenic climate change.

Here we present results of a multi-proxy provenance study by using K- and plagioclase feldspar, selected due to their relative abundance in clastic sediment, and tendency to incorporate Rb (K-feldspar only), Pb, and Sr at analytically useful concentrations, thus enabling source-terrane fingerprinting. While Pb-isotope fingerprinting is an established method for provenance analysis of glaciogenic sediment (Flowerdew et al., 2012), the combination with in-situ Sr-isotope fingerprinting and ⁸⁷Rb/⁸⁷Sr dating is a novel approach. These techniques are applied to deep-sea core ODP113-694, recovered from the Weddell Sea, ca. 750 km from the continental rise in 4671 m of water. This location is ideal, as it acts as a major iceberg graveyard making it a key IRD depocenter (Barker, Kennett et al., 1988). Within the core, several IRD layers were identified and analysed with preliminary depositional ages of 14.09 to 14.26 Ma.

Our findings are consistent with predictions made by recent palaeo-ice sheet models (eg., Gasson et al. 2016), which predict the development of sizeable and discrete embayments around the continent, including the Weddell Sea. We argue that the IRD derived from the unstable sector associated with this embayment formation at the time.

Barker, P.F., Kennett, J.P., et al., 1988, Proc. Init. Repts. (Pt. A): ODP, 113, College Station, TX (Ocean Drilling Program).

Flowerdew, M.J., et al., 2012, Chemical Geology, v. 292–293, p. 88–102, doi: 10.1016/j.chemgeo.2011.11.006.

Gasson, E, et al., 2016, Proceedings of the National Academy of Sciences, v. 113, (13), p. 3459-3464, doi: www.pnas.org/cgi/doi/10.1073/pnas.1516130113.

Shevenell, A.E., et al., 2004, Science, v. 305, p. 1766-1770, doi: 10.1126/science.1100061.

How to cite: Neofitu, R., Mark, C., O'Connell, S., Kelley, S., Rösel, D., Zack, T., Flowerdew, M., and Daly, J. S.: Tracking ice-sheet dynamics by detrital feldspar Pb-isotope and 87Rb/87Sr dating during the Middle Miocene Climatic Transition, Weddell Sea, Antarctica, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6484, https://doi.org/10.5194/egusphere-egu22-6484, 2022.

Marine sediment cores containing a unique Pliocene paleoenvironmental record were collected from the East Antarctic Wilkes Land continental rise by the IODP Expedition 318 at Site U1361 (Escutia et al., 2011). Site U1361 is located in front of the Wilkes Subglacial Basin (WSB) were, today, the East Antarctic Ice Sheet (EAIS) is grounded below sea level (marine-based) and therefore more vulnerable to climate changes.

We have conducted a facies analysis using shipboard measurements taken during Expedition 318 (i.e., physical properties data such as density (GRA) and magnetic susceptibility (MST) and high-resolution digital images), complemented with continuous elemental geochemical analyses. In addition, we have conducted high-resolution siliceous microfossil analyses to characterize past “warmer-than-present” intervals during the Pliocene warm period (~ 3-5 Ma) and their terminations recorded in site U1361 between ~ 73 to 123 mbsf. Our study is complemented by a pilot high-resolution detailed work on siliceous microfossils conducted from 3.69 to y 3.56 Ma that captures changes in sea ice cover and oceanic conditions (Armbrecht et al., 2018).

Preliminary analyses show that sediments consist of alternating intervals of interglacial diatom-rich/bearing silty clay with dispersed clasts that are ~ 0.5 to 8 m thick, and glacial sparsely laminated bioturbated clays with occasionally dispersed clasts.  In general, interglacial sediments is characterized by lower density, higher MST values, lower Mn/Ti and Fe/Ti ratios, and high Ca/Al, Si/Al, and Ba/Al ratios. Bioturbated clay with any dispersed clasts has a marked opposite trend (i.e., higher density, lower MST values, lower Ca/Al, Si/Al, and Ba/Al ratios and higher Mn/Ti and Fe/Ti ratios). This changes in lithology, physical properties and geochemical composition record significant changes in paleoenvironmental conditions. However, each glacial/interglacial (and vice versa) period exhibit specific characteristics and diatom associations pointing to different sea ice conditions during the selected Pliocene intervalsthat can be indirectly linked to ice-sheet dynamics in the Wilkes Subglacial Basin. The results of this study are relevant in order to understand the response of the EAIS dynamics and marine biota to an increase of the ocean surface temperatures during the transition from atmospheric CO₂ concentrations similar to pre-industrial to concentrations close to present values (410 ppm).

This work has been conducted in the frame of projects H2020-MSCA-IF-2018-ANTICE-841980/CTM2017-89711-C2-1-P and is a contribution to the SCAR INSTANT Program.

Escutia, C. et al., 2011 doi:10.2204/​iodp.proc.318.105.2011

Armbrecht et al., 2018. doi:10.1016/j.marmicro.2017.10.008

How to cite: Gutiérrez-Pastor, J., Escutia, C., Jiménez-Espejo, F. J., Rigual-Hernández, A. S., Bárcena, M. Á., McKay, R., and Morales, C.: Sedimentological facies characterization of Pliocene key interglacial-glacial intervals, IODP site 1361A, East Antarctic Wilkes Land margin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10174, https://doi.org/10.5194/egusphere-egu22-10174, 2022.