Compiling a chemistry database from Antarctic ice cores records spanning the past 2000 years

2021 ◽  
Author(s):  
Diana Vladimirova ◽  
Elizabeth Thomas ◽  
on behalf of CLIVASH2k
Keyword(s):  
Sea Ice ◽  
Atmospheric Circulation ◽  
Large Scale ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Sea Ice Extent ◽  
Large Variability ◽  
The Past ◽  
Direct Observations ◽  
Past 2000 Years

<p>Trends in sea ice extent and atmospheric circulation around Antarctica have exhibited large variability over recent decades. Direct observations such as satellite data cover the past four decades only. Thus, a comparison with paleoclimate archives is essential to understand the natural and anthropogenic components of these recent changes. We have initiated a data call within CLIVASH2k community (http://pastglobalchanges.org/science/wg/2k-network/projects/clivash) to collect all available sodium (Na+) and sulfate (SO42-) concentration and fluxes from Antarctic ice cores. We aim to improve our understanding of large-scale sea-ice variability and atmospheric circulation over the past 2000 years. In this respect, ice cores are a unique archive.</p><p>Here we present the new database, which builds on previous efforts by the PAGES community in gathering snow accumulation (Thomas et al. 2017) and stable water isotope data (Stenni et al. 2017).  To date, 88 published and 14 unpublished records have been submitted, 10 of which span the full 2000 years. The data, especially 2000 years-long records are equally distributed over the Antarctic continent and all coastal regions are well represented.  The new data will allow us to investigate interannual and decadal-to-centennial scale variability in sea ice extent and atmospheric circulation and its regional differences over the past 2000 years.</p>

scholarly journals The Ross Sea Dipole – temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years

2018 ◽  
Vol 14 (2) ◽  
pp. 193-214 ◽  
Author(s):  
Nancy A. N. Bertler ◽  
Howard Conway ◽  
Dorthe Dahl-Jensen ◽  
Daniel B. Emanuelsson ◽  
Mai Winstrup ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ross Sea ◽  
Ice Core ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Ice Age ◽  
West Antarctica ◽  
Isotopic Enrichment ◽  
The Past ◽  
Western Ross Sea

Abstract. High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979–2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE.

scholarly journals Snow-Pit Record from a Coastal Antarctic Site and Its Preservation of Meteorological Features

2021 ◽  
Vol 25 (1) ◽  
pp. 108-118
Author(s):  
Yalalt Nyamgerel ◽  
Sang-Bum Hong ◽  
Yeongcheol Han ◽  
Songyi Kim ◽  
Jeonghoon Lee ◽  
...  
Keyword(s):  
Sea Ice ◽  
Air Temperature ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Sea Salt ◽  
Temperature Record ◽  
Sea Ice Extent ◽  
Environmental Signals ◽  
Salt Ions ◽  
Polar Snow

Abstract Polar snow pits or ice cores preserve valuable information derived from the atmosphere on past climate and environment changes. A 1.57-m snow-pit record from the coastal site (Styx Glacier) in eastern Antarctica covering the period from January 2011 to January 2015 was discussed and compared with meteorological variables. The dominant contribution of the deposition of sea-salt aerosols due to the proximity of the site to the ocean and processes of sea ice formation was revealed in the ionic concentrations. Consistent seasonal peaks in δ 18 O, δ D, MSA, , and indicate the strong enhancement of their source during warm periods, whereas the sea-salt ions (Na + , K + , Mg 2+ , Ca 2+ , Cl − , and ) exhibit a distinct distribution. Monthly mean δ 18 O positively correlates with the air temperature record from an automatic weather station (AWS) located in the main wind direction. Despite the shortness of the record, we suspect that the slight depletion of the isotopic composition and lowering of the snow accumulation could be related to the cooler air temperature with the decrease of open sea area. Consistency with previous studies and the positive correlation of sea-salt ions in the snow pit indicate the relatively good preservation of snow layers with noticeable climate and environmental signals [e.g., changes in sea ice extent (SIE) or sea surface temperature]. We report a new snow-pit record, which would be comparative and supportive to understand similar signals preserved in deeper ice cores in this location.

Examining the strength of the link between surface temperature and surface mass balance in ice cores and models over the last centuries in Antarctica

2020 ◽  
Author(s):  
Marie G. P. Cavitte ◽  
Quentin Dalaiden ◽  
Hugues Goosse ◽  
Jan T.M. Lenaerts ◽  
Elizabeth R. Thomas
Keyword(s):  
Large Scale ◽  
Ice Core ◽  
Ice Sheets ◽  
Ice Cores ◽  
Regional Model ◽  
Snow Accumulation ◽  
Surface Mass Balance ◽  
Weak Correlation ◽  
Surface Mass ◽  
The Past

<p>Ice cores constitute an important record of the past surface mass balance (SMB) of the ice sheets, with SMB ultimately modulating the ice sheets’ sea level impact. For the Antarctic Ice Sheet (AIS), SMB is dominated by snow accumulation and strongly controlled by atmospheric circulation. Large-scale atmospheric depressions collect warmth and moisture from further north that they then release over the AIS in the form of widespread accumulation or focused atmospheric rivers. This implies that snow deposited at the surface of the AIS should show strongly coupled SMB and surface air temperatures (SAT) variations. Ice cores do not record SAT directly but their d<sup>18</sup>O record is often used as a temperature proxy.</p><p> </p><p>Here, using the PAGES 2k Network ice core compilations of SMB and d<sup>18</sup>O of Thomas et al. (2017) and Stenni et al. (2017), we obtain a weak correlation between SMB and d<sup>18</sup>O over historical timescales, and an equivalently weak correlation between SMB and SAT based on the Nicolas & Bromwich (2014) SAT reconstructions. However, we calculate a strong and positive SMB-SAT correlation in the majority of regions of the AIS using Global Climate Models (GCM) and the regional model RACMO2.3p2.</p><p> </p><p>To resolve the discrepancy between measured and modeled signals, we show that averaging the ice core records in close spatial proximity increases their SMB-SAT correlation. This increase in measured SMB-SAT correlation likely results from noise present in the ice core records, but is not enough to match the strong correlation calculated in the models. On the model side, the high spatial resolution of the RACMO2.3p2 model allows us to highlight a number of areas of the AIS where SMB and SAT are not strongly correlated. We describe how wind-driven processes acting on the SMB and SAT locally, through Foehn and katabatic effects, can overwhelm the large-scale atmospheric input that induces the positive SMB-SAT correlations. In particular, we focus on Dronning Maud Land, East Antarctica, where each ice promontory clearly shows this wind-driven snow redistribution. Nevertheless, those regions displaying a low SMB-SAT correlation cover only a small fraction of the AIS and are not sufficient to explain the model-data discrepancy, suggesting a critical role of processes at a scale smaller than the one resolved by the regional model.</p><p> </p><p>References:</p><p>Thomas, E. R., 2017, Regional Antarctic snow accumulation over the past 1000 years, Climate of the Past, 13, 1491–1513.</p><p>Stenni, B. et al., 2017, Antarctic climate variability on regional and continental scales over the last 2000 years, Climate of the Past, 13, 1609–1634.</p><p>Nicolas, J. P. & Bromwich, D. H., 2014, New reconstruction of Antarctic near-surface temperatures: Multidecadal trends and reliability of global reanalyses, Journal of Climate, 27, 8070–8093.</p>

scholarly journals Antarctic Sea Ice Proxies from Marine and Ice Core Archives Suitable for Reconstructing Sea Ice over the Past 2000 Years

Geosciences ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 506 ◽  
Author(s):  
Elizabeth R. Thomas ◽  
Claire S. Allen ◽  
Johan Etourneau ◽  
Amy C. F. King ◽  
Mirko Severi ◽  
...  
Keyword(s):  
Sea Ice ◽  
20Th Century ◽  
Climate Models ◽  
Ross Sea ◽  
Ice Core ◽  
Ice Cores ◽  
Weddell Sea ◽  
The Past ◽  
Antarctic Sea Ice ◽  
Past 2000 Years

Dramatic changes in sea ice have been observed in both poles in recent decades. However, the observational period for sea ice is short, and the climate models tasked with predicting future change in sea ice struggle to capture the current Antarctic trends. Paleoclimate archives, from marine sedimentary records and coastal Antarctic ice cores, provide a means of understanding sea ice variability and its drivers over decadal to centennial timescales. In this study, we collate published records of Antarctic sea ice over the past 2000 years (2 ka). We evaluate the current proxies and explore the potential of combining marine and ice core records to produce multi-archive reconstructions. Despite identifying 92 sea ice reconstructions, the spatial and temporal resolution is only sufficient to reconstruct circum-Antarctic sea ice during the 20th century, not the full 2 ka. Our synthesis reveals a 90 year trend of increasing sea ice in the Ross Sea and declining sea ice in the Bellingshausen, comparable with observed trends since 1979. Reconstructions in the Weddell Sea, the Western Pacific and the Indian Ocean reveal small negative trends in sea ice during the 20th century (1900–1990), in contrast to the observed sea ice expansion in these regions since 1979.

scholarly journals Reconstructing atmospheric circulation and sea-ice extent in the West Antarctic over the past 200 years using data assimilation

2021 ◽  
Author(s):  
Quentin Dalaiden ◽  
Hugues Goosse ◽  
Jeanne Rezsohazy ◽  
Elizabeth R. Thomas
Keyword(s):  
Data Assimilation ◽  
Sea Ice ◽  
Ross Sea ◽  
Snow Accumulation ◽  
The West ◽  
Sea Ice Extent ◽  
Amundsen Sea ◽  
The Past ◽  
West Antarctic

Abstract The West Antarctic climate has witnessed large changes during the second half of the 20th century including a strong and widespread continental warming, important regional changes in sea-ice extent and snow accumulation, as well as a major mass loss from the melting of some ice shelves. However, the potential links between those observed changes are still unclear and instrumental data do not allow determination of whether they are part of a long-term evolution or specific to the recent decades. In this study, we analyze the climate variability of the past two centuries in the West Antarctic sector by reconstructing the key atmospheric variables (atmospheric circulation, near-surface air temperature and snow accumulation) as well as the sea-ice extent at the annual timescale using a data assimilation approach. To this end, information from Antarctic ice core records (snow accumulation and δ 18 O and tree-ring width records situated in the mid-latitudes of the Southern Hemisphere are combined with the physics of climate models using a data assimilation method. This ultimately provides a complete spatial reconstruction over the west Antarctic region. Our reconstruction reproduces well the main characteristics of the observed changes over the instrumental period. We show that the observed sea-ice reduction in the Bellingshausen-Amundsen Sea sector over the satellite era is part of a long-term trend, starting at around 1850 CE, while the sea-ice expansion in the Ross Sea sector has only started around 1950 CE. Furthermore, according to our reconstruction, the Amundsen Sea Low pressure (ASL) displays no significant linear trend in its strength or position over 1850--1950 CE but becomes stronger and shifts eastward afterwards. The year-to-year sea-ice variations in the Ross Sea sector are strongly related to the ASL variability over the past two centuries, including the recent trends. By contrast, the link between ASL and sea-ice in the Bellingshausen-Amundsen Sea sector changes with time, being stronger in recent decades than before. Our reconstruction also suggests that the continental response to the variability of the ASL may not be stationary over time, being significantly affected by modification of the mean circulation. Finally, we show that the widespread warming since 1958 CE in West Antarctica is unusual in the context of past 200 years and is explained by both the deeper ASL and the positive phase of the Southern Annular Mode.

scholarly journals Reconstructing atmospheric circulation and sea-ice extent in the West Antarctic over the past 200 years using data assimilation 

2021 ◽  
Author(s):  
Quentin Dalaiden ◽  
Hugues Goosse ◽  
Jeanne Rezsohazy ◽  
Elizabeth R. Thomas
Keyword(s):  
Data Assimilation ◽  
Sea Ice ◽  
Ross Sea ◽  
Snow Accumulation ◽  
The West ◽  
Sea Ice Extent ◽  
Amundsen Sea ◽  
The Past ◽  
West Antarctic

<p>Ocean and ice sheet in the West Antarctic sector have witnessed large climate changes during the second half of the 20<sup>th</sup> century including a strong and widespread continental warming, important regional changes in sea-ice extent and snow accumulation, as well as a major mass loss from the melting of some ice shelves. However, the potential links between those observed changes are still unclear and instrumental data do not allow determining if they are part of a long-term evolution or specific to the recent decades. In this study, we analyze the climate variability of the past two centuries in the West Antarctic sector by reconstructing the key atmospheric variables (atmospheric circulation, near-surface air temperature and snow accumulation) as well as the sea-ice extent at the annual timescale using a data assimilation approach. To this end, information from Antarctic ice core records (snow accumulation and δ<sup>18</sup>O) and tree-ring width sites located in the mid-latitudes of the Southern Hemisphere are combined with the physics of climate models using a data assimilation method. This ultimately provides a complete spatial reconstruction over the west Antarctic region. Our reconstruction reproduces well the main characteristics of the observed changes over the instrumental period. We show that the observed sea-ice reduction in the Bellingshausen-Amundsen Sea sector over the satellite era is part of a long-term trend, starting at around 1850 CE, while the sea-ice expansion in the Ross Sea sector has only started around 1950 CE. Furthermore, according to our reconstruction, the Amundsen Sea Low pressure (ASL) displays no significant linear trend in its strength or position over 1850-1950 CE but becomes stronger and shifts eastward afterwards. The year-to-year sea-ice variations in the Ross Sea sector are strongly related to the ASL variability over the past two centuries, including the recent trends. By contrast, the link between ASL and sea ice the Bellingshausen-Amundsen Sea sector changes with time, being stronger in recent decades than before, Our reconstruction also suggests that the continental response to the variability of the ASL may not be stationary over time, being significantly affected by modification of the mean circulation. Finally, we show that the widespread warming since 1958 CE in West Antarctica is unusual in the context of past 200 years and is explained by both the deeper ASL and the positive phase of the Southern Annular Mode.</p>

scholarly journals The Ross Sea Dipole – Temperature, Snow Accumulation and Sea Ice Variability in the Ross Sea Region, Antarctica, over the Past 2,700 Years

2017 ◽  
Author(s):  
Nancy A. N. Bertler ◽  
Howard Conway ◽  
Dorthe Dahl-Jensen ◽  
Daniel B. Emanuelsson ◽  
Mai Winstrup ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ross Sea ◽  
Ice Core ◽  
Reanalysis Data ◽  
Snow Accumulation ◽  
West Antarctica ◽  
Dynamic Interactions ◽  
Sea Ice Extent ◽  
The Past ◽  
Western Ross Sea

Abstract. High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually-dated ice core record from the eastern Ross Sea. Comparison of the Roosevelt Island Climate Evolution (RICE) ice core records with climate reanalysis data for the 1979–2012 calibration period shows that RICE records reliably capture temperature and snow precipitation variability of the region. RICE is compared with data from West Antarctica (West Antarctic Ice Sheet Divide Ice Core) and the western (Talos Dome) and eastern (Siple Dome) Ross Sea. For most of the past 2,700 years, the eastern Ross Sea was warming with perhaps increased snow accumulation and decreased sea ice extent. However, West Antarctica cooled whereas the western Ross Sea showed no significant temperature trend. From the 17th Century onwards, this relationship changes. All three regions now show signs of warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea, but increasing in the western Ross Sea. Analysis of decadal to centennial-scale climate variability superimposed on the longer term trend reveal that periods characterised by opposing temperature trends between the Eastern and Western Ross Sea have occurred since the 3rd Century but are masked by longer-term trends. This pattern here is referred to as the Ross Sea Dipole, caused by a sensitive response of the region to dynamic interactions of the Southern Annual Mode and tropical forcings.

Seasonal variations in the properties and structural composition of sea ice and snow cover in the Bellingshausen and Amundsen Seas, Antarctica

1997 ◽  
Vol 43 (143) ◽  
pp. 138-151 ◽  
Author(s):  
M. O. Jeffries ◽  
K. Morris ◽  
W.F. Weeks ◽  
A. P. Worby
Keyword(s):  
Sea Ice ◽  
Isotopic Composition ◽  
Snow Cover ◽  
Sea Water ◽  
Ice Cores ◽  
Ice Cover ◽  
Snow Accumulation ◽  
Ice Formation ◽  
Frazil Ice ◽  
Core Sets

AbstractSixty-three ice cores were collected in the Bellingshausen and Amundsen Seas in August and September 1993 during a cruise of the R.V. Nathaniel B. Palmer. The structure and stable-isotopic composition (18O/16O) of the cores were investigated in order to understand the growth conditions and to identify the key growth processes, particularly the contribution of snow to sea-ice formation. The structure and isotopic composition of a set of 12 cores that was collected for the same purpose in the Bellingshausen Sea in March 1992 are reassessed. Frazil ice and congelation ice contribute 44% and 26%, respectively, to the composition of both the winter and summer ice-core sets, evidence that the relatively calm conditions that favour congelation-ice formation are neither as common nor as prolonged as the more turbulent conditions that favour frazil-ice growth and pancake-ice formation. Both frazil- and congelation-ice layers have an av erage thickness of 0.12 m in winter, evidence that congelation ice and pancake ice thicken primarily by dynamic processes. The thermodynamic development of the ice cover relies heavily on the formation of snow ice at the surface of floes after sea water has flooded the snow cover. Snow-ice layers have a mean thickness of 0.20 and 0.28 m in the winter and summer cores, respectively, and the contribution of snow ice to the winter (24%) and summer (16%) core sets exceeds most quantities that have been reported previously in other Antarctic pack-ice zones. The thickness and quantity of snow ice may be due to a combination of high snow-accumulation rates and snow loads, environmental conditions that favour a warm ice cover in which brine convection between the bottom and top of the ice introduces sea water to the snow/ice interface, and bottom melting losses being compensated by snow-ice formation. Layers of superimposed ice at the top of each of the summer cores make up 4.6% of the ice that was examined and they increase by a factor of 3 the quantity of snow entrained in the ice. The accumulation of superimposed ice is evidence that melting in the snow cover on Antarctic sea-ice floes ran reach an advanced stage and contribute a significant amount of snow to the total ice mass.

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