Understanding the climate of the past two millennia (2k) remains vital for developing our wider comprehension of the climate system, including the nature and scale of recent and future anthropogenic change. Phase 4 of the PAGES 2k network will build on previous phases and take us to a new level of understanding and science-policy integration.

During previous phases, PAGES 2k members compiled global networks of proxy measurements, extending records beyond the instrumental period by more than an order of magnitude, reconstructing past climate and developing new knowledge of past variability and processes. Through data-model integration with state-of-the-art Earth systems models, proxy system modelling and data assimilation, we took key steps towards a more comprehensive understanding of climate dynamics.

Phase 4 will take us even further, challenging our community to turn its focus primarily towards the hydroclimate of the Common Era: performing new reconstructions and improving the interoperability, extent and scope of our data and model products. In doing so, we also seek to facilitate the translation of our science into evidence-based policy outcomes. Our overarching aim is to reconstruct hydroclimate variability over the Common Era from local to global spatial scales, at sub-annual to multi-centennial time scales. We propose to achieve this through new community-led data curation efforts and the development of new data-driven tools and practices to maximise the interoperability of convenient, efficient and widespread model/data products. We will aim for a process-level understanding of past hydroclimate events and variability by evaluating and constraining Earth system models and through data assimilation.

Our coordination team places a strong emphasis on respect and inclusion, aiming to foster a diverse and equitable community. Through a ‘hub and spoke’ structure, our team will provide a facilitation, coordination and support role (the hub) for Pages 2k working groups (the spokes). We are actively seeking participation of those engaging in climate policy and climate services. Welcome to Phase 4!  We warmly invite your collaborations and contributions! 

How to cite: Henley, B., Eggleston, S., Kaushal, N., Atwood, A., Bothe, O., Falster, G., Jones, M., Jonkers, L., Konecky, B., Linderholm, H., Martrat, B., McGregor, H., Orsi, A., Phipps, S., and Sayani, H.: Announcing Phase 4 of PAGES 2k: Hydroclimate of the Common Era, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6688, https://doi.org/10.5194/egusphere-egu22-6688, 2022.

We present a 50-member global monthly gridded Sea Surface Temperature (SST) and Sea Ice Concentration (SIC) dataset covering 850 years (1000–1849). The SST fields are based on an existing coarse-resolution ensemble of annual reconstructions and augmented with intra-annual and sub-grid scale variability, such that the annual means of the coarse resolution SST reconstructions are preserved. We utilize a large body of historical observational inputs from ICOADS (1780 – 1849) in an offline data assimilation approach.

Furthermore, the best sea ice analogs are selected based on a measure of similarity between subpolar and midlatitude SSTs of our reconstruction and HadISST SIC. The resulting SST and SIC fields will reflect a spatially and temporal consistent representation of the historical state of the ocean and are reconstructed to be used as forcing for AGCM simulations.

Reference:

Samakinwa, E., Valler, V., Hand, R. et al. An ensemble reconstruction of global monthly sea surface temperature and sea ice concentration 1000–1849. Sci Data 8, 261 (2021). https://doi.org/10.1038/s41597-021-01043-1

How to cite: Samakinwa, E., Valler, V., Hand, R., and Brönnimann, S.: Global monthly sea surface temperature and sea ice reconstruction for historical AGCM simulations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11664, https://doi.org/10.5194/egusphere-egu22-11664, 2022.

In order to improve the climate reconstruction quality and better understand last millennium temperature variability, a reservoir computing (RC) method: Echo State Network (ESN) is applied for the reconstruction of the North Hemisphere summer seasonal temperature. ESN, a specialized type of recurrent neural network method, belongs to the family of machine learning methods, which is suitable for mapping complex systems with chaotic dynamics, for instance the hemisphere temperature variability. ESN is the widely implementation of RC and employs a structure with neuron-like nodes and recurrent connections, the internal reservoir, to handle the sequential data. It consists of three layers: input layer, reservoir layer and output layer; a randomly generated reservoir in ESN preserves a set of nonlinear transformations of the input data and a linear regression criterion is employed for its training process to optimize the parameters. ESN could provide an alternative nonlinear machine learning method that might improve the prediction or reconstruction skills of paleoclimate. In this context, we first conduct pseudoproxy experiments (PPEs) using three different Earth System Models (ESM), including Community Climate System Model CCSM4, the Max-Planck-Institute climate model MPI-ESM-P and the Community Earth System Model CESM1-CAM5. Two classical multivariable linear regression methods, Principal component regression and Canonical correlation analysis, are also employed as a benchmark. Among the three models providing climate simulations of the past millennium, both derived spatial and temporal reconstruction results based on PPEs demonstrate that ESN could capture more variance than other two classical methods, and could potentially achieve paleo-temperature reconstruction improvements. This suggests that the ESN machine learning method could be an alternative method for paleoclimate analysis.

How to cite: Zhang, Z., Wagner, S., and Zorita, E.: Reconstructions of North Hemisphere summer temperature based on tree-ring proxies using linear and machine learning methods, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1491, https://doi.org/10.5194/egusphere-egu22-1491, 2022.

Annual-to-decadal variability in northern midlatitude temperature is predominantly dominated by the cold season. However, climate field reconstructions, which are essential for understanding the underlying mechanisms, are often based on tree rings. These mainly represent the growing season and allow limited insight on cold season effects. Plant and ice phenology data, on the other hand, are a rich source of cold season information that remains largely overlooked in climate reconstructions to date and could help to fill the seasonal gap. Here, we present Northern Hemispheric temperature field reconstructions for the extended cold season (October-to-May average) for 1701-1905 based entirely on phenological data. Time series of freezing and thawing dates of rivers together with a few early-spring plant observations covering a large area of the northern midlatitudes are used in a simple data assimilation framework.
The reconstructions allow a 320-yr perspective of climate variability and change of boreal cold season climate and unveil that the temperature of the northern midlatitude land areas exceeded the variability range of the 18th and 19th centuries by the 1940s, to which recent warming has added another 1.5 °C. We also find 5-10 year long sequences of cold northern midlatitude winters. The most prominent example lasted from 1808/9 to 1815/6. The conspicuously cooling during that period is associated with two volcanic eruptions (1808/9 and 1815), which caused cooling as a direct effect. The years between the eruptions are characterized by weak southwesterly atmospheric flow over the Atlantic-European sector in early winter. This lead to low Eurasian temperatures, which persisted into spring while the flow pattern did not. Twentieth century data and model simulations confirm this persistence and point to increased snow cover as a cause. This is consistent with independent information on Eurasian snow in the early 19th century.

How to cite: Burgdorf, A.-M., Brönnimann, S., Reichen, L., Franke, J., Hand, R., Valler, V., Samakinwa, E., Burgnara, Y., and Rutishauser, T.: Novel Cold Season Temperature Field Reconstructions for the Northern Midlatitudes from Phenological Data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9639, https://doi.org/10.5194/egusphere-egu22-9639, 2022.

The thermal regime of the Arctic subsurface is important, for example, in the context of greenhouse-gas release from thawing permafrost soils. Measurements of Arctic subsurface temperatures, however, are scarce and limited in time, with virtually no observations over climatological time scales. We address this gap in knowledge by estimating the long-term evolution of subsurface temperatures in the Arctic (north of 60ºN) since 1600 Common Era (CE) to the present using 110 deep subsurface temperature profiles. The Arctic subsurface has warmed by 1.7±0.8 ºC during 1970-2000 CE. These estimates are conservative, as the effects of latent heat are not included in the analysis. Although there are significant spatial variations, the Arctic subsurface is warming faster than the global land surface and subsurface (1.2±0.2 ºC) during the same period. Uncertainties in this analysis arise mostly from deficient knowledge about the subsurface physical properties and limited data coverage.

How to cite: Cuesta-Valero, F. J., Beltrami, H., García-García, A., Jaume-Santero, F., and Gruber, S.: Arctic Warming: A Perspective from the Underground, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1838, https://doi.org/10.5194/egusphere-egu22-1838, 2022.

This study conducted a comprehensive analysis of climate responses to volcanic eruptions occurred at different latitudes considering the last millennium volcanic eruptions available from Community Earth System Model ensemble simulations. Especially, we examine how different eruption latitudes induce the different responses in Arctic Oscillation (AO) with polar vortex and thereby exert different influences on northern Eurasian climate. We classify volcanic eruptions as tropical, northern and southern eruptions based on hemispheric aerosol loading ratios, which have different meridional structure of solar radiation perturbations and cause asymmetric climate response patterns between hemispheres, including tropospheric cooling and lower stratospheric warming. Volcanic eruptions found to cause stronger stratospheric polar vortex in both hemispheres with varying magnitudes depending on eruption latitudes. Following the tropical and southern eruptions, polar vortex enhancement is found in both hemispheric polar regions due to enhanced pole-to-equator temperature gradient and equatorward propagation of planetary waves. As a result of boreal winter averaged polar vortex enhancement, the tropical and southern eruptions found to cause more probability to occur at least the pentad strong polar vortex events during the boreal winter, which leads tropospheric westerly wind anomalies after a few days to the events. As a result, positive AO-like responses emerge at the lower troposphere. The positive AO induces surface air temperature warming as well as precipitation increase over the northern Eurasian continental regions. Following southern eruptions, the AO, Eurasian warming and wetting responses are much more extended to more southward (NH mid-latitudes) due to the more equatorward extended polar vortex variation. On the other hand, the Arctic polar vortex and the associated surface responses are only weakly influenced by the northern eruptions, in line with much poleward spread of volcanic aerosols and lesser equatorward extended planetary wave propagation in the lower stratosphere. These results suggest that while volcanic eruptions modulate surface climate by strengthening the polar vortex, their impacts are dependent on the eruption latitudes.

How to cite: Paik, S., Min, S.-K., Son, S.-W., An, S.-I., Kug, J.-S., and Yeh, S.-W.: Diverse Arctic Oscillation responses after volcanic eruptions at different latitudes during the last millennium, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10958, https://doi.org/10.5194/egusphere-egu22-10958, 2022.

The Atlantic Multidecadal Variability (AMV) modulates the North Atlantic surface ocean variability and affects decadal climate evolution up to the global scale; however, the underlying mechanisms of the AMV remains debated. We use a multi-model ensemble of transient past-millennium and unperturbed preindustrial control simulations contributing to the Paleoclimate Modelling Intercomparison Project - Phase 4 (PMIP4) to decompose the AMV signal into its internal and external components. The internal component of AMV exhibits no robust behavior across simulations during periods of major forcing such as strong volcanic eruptions, whereas the externally-forced component of AMV responds to volcanic eruptions with an immediate radiative cooling followed, in some simulations, by a sequence of damped multidecadal oscillations. This indicates that the intrinsic mechanism underlying the AMV is distinguishable from its response to external forcing. The internal component of AMV is tightly connected with the Atlantic meridional overturning circulation (AMOC) and controls the variations of AMV. The external component of AMV explains about 25% of the variance in the past millennium simulations, though less-consistency is found between models. Our results further indicate that the spatial imprint of external volcanic forcing on North Atlantic sea-surface temperatures differs from the surface pattern of the internal AMV contributing to the lack of robustness for the AMV pattern.

How to cite: Fang, S.-W., Khodri, M., Timmreck, C., Zanchettin, D., and Jungclaus, J.: Disentangling Internal and External Contribution to Atlantic Multidecadal Variability over Past Millennium, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9547, https://doi.org/10.5194/egusphere-egu22-9547, 2022.

Long-lived colonial cold-water corals have the potential to provide robust continuous archives of environmental change. These high-resolution records of the subsurface ocean are particularly valuable, especially at understudied intermediate water depths. Yet, to understand the anthropogenic impacts on the sub-surface ocean and better predict future changes, it is critical to establish the natural variation of temperature and circulation of the ocean system prior to the Industrial Revolution.

Here we combine temperature proxy and radiocarbon data from specimens of two taxa of cold-water coral that grew in intermediate water depths (~1500 m) in the tropical North Atlantic. In 2013, specimens of the bamboo coral Lepidisis spp. and scleractinian coral Enallopsammia rostrata were collected from sites currently situated in the boundary of North Atlantic Deep Water and Antarctic Intermediate Water to reconstruct the temperature and circulation history of the region. We demonstrate that bamboo corals can be used to reconstruct ambient seawater radiocarbon content when independently dated by organic node annual band counting. Radiocarbon was also analysed in Enallopsammia rostrata to develop age models for both the radial section and from discrete corallites (polyps) along a branch. Dating results show that this coral is about 500 years old, allowing us to generate a temperature record as far back as the Little Ice Age. Trace metal ratios were analysed along the growth axis of the coral, and the Li/Mg ratio was used as a temperature proxy. We find that the Li/Mg derived temperature of the most recent polyps is consistent with modern ambient temperature. The overall temperature record shows a general increasing trend since the Little Ice Age, while the radiocarbon record indicates no significant change until the late 20^th century. Combining these records allows us to reconstruct potential ocean circulation changes in the central tropical North Atlantic over last 500 years.

How to cite: Liu, Q., Robinson, L. F., Hendy, E., Chen, S.-Y. S., Stewart, J. A., Knowles, T., Li, T., and Samperiz Vizcaino, A.: Reconstruction of intermediate water temperature in the tropical North Atlantic since the Little Ice Age using cold-water corals , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5745, https://doi.org/10.5194/egusphere-egu22-5745, 2022.

Climate extremes over the mid-latitudes are driven by a combination of thermodynamical and dynamical factors. In Europe, the primary dynamical driver of summer climate extremes is the position of the jet stream over the Europe-North Atlantic (EU) region. In certain configurations, the EU jet creates a summer climate dipole between northwestern and southeastern Europe that can result in contrasting extreme weather conditions in the two regions. To study long-term variability in the EU jet configuration, as well as its potential impact on past climate extremes and human systems, we have reconstructed EU jet variability over the past 800+ years (1200-2005 CE). To accomplish this, we have combined five European tree-ring chronologies to reconstruct the July-August jet stream latitude for the EU domain (30°W - 40°E; EU JSL). Our reconstruction explains 40% of summer EU JSL variability over the instrumental period (1948-2005 CE) with strong skill.

We find that, over the past 800 years, opposite phases of EU JSL variability have consistently resulted in contrasting climate extremes, including heatwaves, droughts, floods, and wildfires, between northwestern Europe, specifically the British Isles, and southeastern Europe, specifically the Balkans and Italy. This EU JSL-driven summer climate dipole is captured in a network of historical documentary data that further document the societal impacts of EU JSL-related climate extremes on both sides of the dipole.

Our summer EU JSL reconstruction shows a century-long negative phase from ca. 1355-1450 CE, corresponding to anomalously wet and cool summers over the British Isles and dry and hot conditions over the Balkans. This negative phase is comparable to the recent (1970-present) EU JSL configuration. We also found a positive phase, with opposite summer climate dipole conditions, from ca. 1812-1861 CE. Our results thus suggest that the EU JSL has been a long-term primary driver of the European summer climate dipole, as well as of the associated climate extremes and societal impacts.

How to cite: Xu, G., Broadman, E., Meko, M., Klippel, L., Ludlow, F., Dorado-Liñan, I., Esper, J., and Trouet, V.: 800 years of summer European-North Atlantic jet stream variability and its impact on climate extremes and human systems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3331, https://doi.org/10.5194/egusphere-egu22-3331, 2022.

Despite their pivotal role in climate research, direct instrumental records of meteorological variables are only available for the most recent part of climate history. Even in regions with longest tradition of weather measurements, such as central Europe, the existing series rarely comprise more than two centuries of reliable data. However, documentary sources, both quantitative and qualitative, can be employed to substantially extend the available records. Using the resulting multi-centennial data, previously unexplored features of climate system’s evolution can then be studied.

In this analysis, temporal variability in annual and seasonal series of temperature, precipitation and drought indices (Standardized Precipitation Index - SPI, Standardized Precipitation Evapotranspiration Index - SPEI, Z-index), pertaining to the territory of contemporary Czechia, has been studied over the 1501–2020 CE period. The series under investigation were reconstructed from multitude of Czech documentary data sources, combined with instrumental observations. Phenoclimatic temperature and SPEI reconstructions, derived from historical records of cereal and grape harvest dates, were also employed and compared to their documentary-based counterparts.

Statistical attribution analysis, utilizing multiple linear regression, confirmed the influence of covariates related to volcanic activity (prompting temporary temperature decreases, especially during summer) and the North Atlantic Oscillation (influential in all seasons except summer for all target variables) in the Czech climate reconstructions. Statistically significant components correlated with multidecadal variability in the northern Atlantic and northern Pacific (represented by multiproxy-reconstructed AMO and PDO indices) were identified in the Czech temperature and precipitation series as well as in all drought indices. Additionally, using wavelet and cross-wavelet analysis, notable oscillations shared by the AMO/PDO variations and the Czech climate series were found, particularly at periods of approximately 70–100 years.

How to cite: Mikšovský, J., Brázdil, R., Dobrovolný, P., Pišoft, P., Trnka, M., Možný, M., and Balek, J.: Temporal variability in central European climate reconstructions, 1501–2020 CE, and its attribution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4140, https://doi.org/10.5194/egusphere-egu22-4140, 2022.

The aim of this study is to reconstruct winter climatic conditions during Medieval Warm Period (MWP) and LIA (Little Ice Age) based on the stable isotopes analyses on two parallel ice cores extracted from Scărișoara Ice Cave, Romania. Based on the analysis of δ¹⁸O data we identified two distinct periods: a warm Medieval Warm Period, (MWP, between AD 850 and 1250) and a cold the Little Ice Age (LIA, between AD 1450 and 1860), separated by a transition period (between AD 1250 and 1450). Further, deuterium excess (d-excess, d = δ²H-8*δ¹⁸O) indicates that during the MWP, air masses were predominantly originating from a dry source between AD 890 and 1000 (likely the Mediterranean Sea) and a generally wet source after ca. AD 1000 (likely, the Atlantic Ocean and/or the Western Mediterranean Sea). During the Transition Period both air temperature and moisture sources had major fluctuations. During the early LIA,  winters were generally cold and humid, while in the second half, winters were cold and dry. Ice accumulation rates, which are the result of winter accumulation and summer ablation, varied widely during the last 1000 years, with strong melting occurring during periods of increased summer rains and/or reduced winter accumulation. Comparing our data with summer climate reconstructions from the same region suggest that both the warm MWP and the cold LIA were predominantly feature of winter climate variability, summer temperatures being much stable during the last millennium.

How to cite: Badaluta, C.-A. and Persoiu, A.: Winter climatic conditions in Western Carpathian Mountains (Eastern Europe) during last millenium, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11624, https://doi.org/10.5194/egusphere-egu22-11624, 2022.

We assess, within a framework of consistent statistical analysis, the inter-annual temperature and hydroclimate signal on grain harvest yields across diverse environmental settings of Europe during the early modern period (c. 1500–1800). To this end, we consider both different grain types and various climate parameters. We go beyond previous studies by applying identical analyses to several regions, by using a larger number of grain yield and harvest records, and by employing a more extensive and diverse set of the latest generation of annually resolved palaeoclimate reconstructions and early instrumental datasets. Hitherto, regional inter-comparisons of historical climate–yield relationships have been constrained by the application of different data and statistical methods. We pay particular attention to the issue of statistical significance in the presence of strong auto-correlation in both the harvest and climate data. Our analyses also consider various seasonal targets, crop types, frequency bands, and lagged harvest responses to climate. Overall, a comparatively weak climate–yield relationship is found, which is consistent with modern observations, as opposed to a strong climate signal we previously have found embedded in early modern grain price data.

How to cite: Charpentier Ljungqvist, F., Christiansen, B., Esper, J., Huhtamaa, H., Leijonhufvud, L., Seim, A., Skoglund, M. K., and Thejll, P.: Climatic impacts on early modern European grain harvest yields, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12340, https://doi.org/10.5194/egusphere-egu22-12340, 2022.

We preliminary investigate potential effects of climate change on Egypt water wise, and adaptation thereby based upon wisdom from the ancient Egyptians. Recent investigation linked socio-economic crises, and collapse events of ancient Egypt since 2200 BC to climate, e.g., droughts, and floods of the Nile, and heavy rainfalls in Northern Egypt. Dry, arid spells were associated to decrease of summer precipitation in the Ethiopian Highlands, while intensive rainfalls could be triggered by the North Atlantic Oscillation.

Here we couple climate, and hydrological modelling, with archaeological and historical investigation, to understand long-term adaptation to the ever-changing climate. We assess past climate of Egypt and consequent changing hydrology of the Nile, including situations of flood risk and food insecurity. We highlight a nexus between changing in climate and hydrology, conflicts, and social disorders.

We tune the Poli-Hydro model for Nile River basin for the XX century, and then use it to simulate future scenarios under climate change projections from six GCMs, of the AR6 of IPCC. We compare future scenarios of climate, and hydrology against past climates patterns. We analyse typical adaptation patterns as from the history of ancient Egypt (e.g. changes of diet, irrigation and cropping strategies, etc.), and we discuss their application for adaption to future climate. Our work may provide a tool to build upon past resilience/adaptation strategies, to conceive viable countermeasures to future climate change here, and in similarly arid areas, to counteract potential food insecurity, flood risk, and conflicts.

How to cite: Casale, F., Fuso, F., Cecchetti, A., and Bocchiola, D.: Learn from the mummies: water wise resilience and adaptation in Egypt along the Nile River., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1105, https://doi.org/10.5194/egusphere-egu22-1105, 2022.

Southern South America (SSA) is one of the regions of the world where the largest trends in precipitation have been recorded during the last 120 years. While South-Eastern South America (SESA) has been affected by a noticeable increase in austral summer rainfall, a remarkable decrease has been observed in Southern Andes (SAn). Moreover, long-term precipitacion has been registered in subtropical Andes and Altiplano regions, which show wetter periods during the 17th century in the Little Ice Age (LIA) and dryer periods during the current Global Warming Period (GWP). In spite of the large impacts related to these trends, the attribution of them is still an open-question. 

This work will assess the attribution of the observed austral summer rainfall trends in SSA to anthropogenic and natural forcings using models available in World Climate Research Programme (WCRP) Coupled Model Intercomparison Project - Phase 5 (CMIP5) and Phase 6 (CMIP6). Analysed experiments include Historical, Pre-Industrial Control and Last Millennium simulations to study long-term changes, as well as the Detection and Attribution Model Intercomparison Project (DAMIP) to assess the attribution of last-century trends. 

The assessment of the Last Millennium simulations allows to detect the following changes in LIA (GWP): (a) equatorwards (polewards) displacement of the southern branch of the Hadley cell, in turn associated with wetter (drier) conditions in subtropical south America; (b) negative (positive) upper-level zonal wind changes related with positive (negative) December, January and February (DJF) rainfall changes in the Altiplano; and (c) positive (negative) low-level zonal wind changes associated to positive (negative) JJA rainfall changes in the subtropical Andes, being in turn related to hemispheric wind changes resembling a negative (positive) phase of the Southern Annular Mode (SAM). The last century changes in the Altiplano reveal a signal associated with the anthropogenic forcing in upper-level zonal wind trends, but it is weak as compared with the internal climate variability. 

Regarding last century trends, positive (negative) rainfall trends in SESA (SAn) are identified in most historical simulations. For both regions, greenhouse-gases-forcing-only simulations show trends consistent with all-forcing simulations, while natural-forcing-only simulations exhibit negligible values. SESA (SAn) shows negative (negligible) trends associated with aerosol-forcing-only simulations and high uncertainty (negative trends) for stratospheric-ozone-forcing-only simulations. Moreover, SAn rainfall trends could be also connected to consistent trends of opposite sign for the Southern Annular Mode (SAM). Overall, our results provide evidence for anthropogenic influences on SSA rainfall trends.

How to cite: Diaz, L. B. and Vera, C. S.: Precipitation trends in Southern South America in the last centuries: attribution and mechanisms, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2059, https://doi.org/10.5194/egusphere-egu22-2059, 2022.

Reconstructions of Antarctic surface air temperature (SAT) covering the past two millennia include some large centennial variabilities that are still not well understood because of the model-data discrepancies. Paleoenvironmental and instrumental observations have highlighted strong interconnections in the Antarctic climate system as illustrated by close relationships between atmosphere and ocean (including sea ice) at all time scales. For instance, over past decades, the Amundsen Sea Low pressure (ASL) is associated with opposite regional sea ice changes in the Bellingshausen-Amundsen and Ross sea sector as well as with variations in snow accumulation over West Antarctica. This inspires us to explore the potentiality of better reconstructing and understanding the drivers of the centennial-scale variability of Antarctic SAT during the Common Era by taking advantage of those links between the Antarctic continental and the Southern Ocean data. To this end, we have compiled proxy-based sea surface temperature reconstructions for the Southern Ocean and qualitative sea-ice reconstructions around Antarctica, together with those having published ice-core based water isotopic and snow accumulation records. We first analyze the continent-ocean relationships by constraining the climate model with continental records through a data assimilation procedure. Results show that we are able to generally reproduce reconstructed variations in the Southern Ocean at centennial scale, particularly for sea surface temperature (SST) along the south Chilean coast and sea ice along the Antarctic Peninsula. In a second step, experiments with data assimilation combining both oceanic and continental records help us to determine how the inclusion of oceanic records improves the reconstruction of the SAT, atmospheric circulation, and sea ice (and SST) over the past two millennia in the high latitudes.

How to cite: Lyu, Z., Goosse, H., Dalaiden, Q., Crosta, X., and Etourneau, J.: Analyzing the continent-ocean relationship in the centennial-scale Antarctic temperature variability over the past 2000 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3061, https://doi.org/10.5194/egusphere-egu22-3061, 2022.