Geophysical constraints on the Antarctic sea ice cover

Abstract The Antarctic sea ice extent has been slowly increasing contrary to expected trends due to global warming and results from coupled climate models. After a record high extent in 2012 the extent was even higher in 2014 when the magnitude exceeded 20 × 106 km2 for the first time during the satellite era. The positive trend is confirmed with newly reprocessed sea ice data that addressed inconsistency issues in the time series. The variability in sea ice extent and ice area was studied alongside surface ice temperature for the 34-yr period starting in 1981, and the results of the analysis show a strong correlation of −0.94 during the growth season and −0.86 during the melt season. The correlation coefficients are even stronger with a one-month lag in surface temperature at −0.96 during the growth season and −0.98 during the melt season, suggesting that the trend in sea ice cover is strongly influenced by the trend in surface temperature. The correlation with atmospheric circulation as represented by the southern annular mode (SAM) index appears to be relatively weak. A case study comparing the record high in 2014 with a relatively low ice extent in 2015 also shows strong sensitivity to changes in surface temperature. The results suggest that the positive trend is a consequence of the spatial variability of global trends in surface temperature and that the ability of current climate models to forecast sea ice trend can be improved through better performance in reproducing observed surface temperatures in the Antarctic region.

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A spurious jump in the satellite record: has Antarctic sea ice expansion been overestimated?

The Cryosphere ◽

10.5194/tc-8-1289-2014 ◽

2014 ◽

Vol 8 (4) ◽

pp. 1289-1296 ◽

Cited By ~ 43

Author(s):

I. Eisenman ◽

W. N. Meier ◽

J. R. Norris

Keyword(s):

Sea Ice ◽

Ice Cover ◽

Current Data ◽

The Arctic ◽

Sea Ice Extent ◽

Data Set ◽

Antarctic Sea Ice ◽

Ice Retreat ◽

Bootstrap Algorithm ◽

The Antarctic

Abstract. Recent estimates indicate that the Antarctic sea ice cover is expanding at a statistically significant rate with a magnitude one-third as large as the rapid rate of sea ice retreat in the Arctic. However, during the mid-2000s, with several fewer years in the observational record, the trend in Antarctic sea ice extent was reported to be considerably smaller and statistically indistinguishable from zero. Here, we show that much of the increase in the reported trend occurred due to the previously undocumented effect of a change in the way the satellite sea ice observations are processed for the widely used Bootstrap algorithm data set, rather than a physical increase in the rate of ice advance. Specifically, we find that a change in the intercalibration across a 1991 sensor transition when the data set was reprocessed in 2007 caused a substantial change in the long-term trend. Although our analysis does not definitively identify whether this change introduced an error or removed one, the resulting difference in the trends suggests that a substantial error exists in either the current data set or the version that was used prior to the mid-2000s, and numerous studies that have relied on these observations should be reexamined to determine the sensitivity of their results to this change in the data set. Furthermore, a number of recent studies have investigated physical mechanisms for the observed expansion of the Antarctic sea ice cover. The results of this analysis raise the possibility that much of this expansion may be a spurious artifact of an error in the processing of the satellite observations.

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A 40-y record reveals gradual Antarctic sea ice increases followed by decreases at rates far exceeding the rates seen in the Arctic

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1906556116 ◽

2019 ◽

Vol 116 (29) ◽

pp. 14414-14423 ◽

Cited By ~ 79

Author(s):

Claire L. Parkinson

Keyword(s):

Sea Ice ◽

Ice Cover ◽

Arctic Sea Ice ◽

The Arctic ◽

Antarctic Sea Ice ◽

Ice Coverage ◽

Yearly Average ◽

Precipitous Decline ◽

The One ◽

The Antarctic

Following over 3 decades of gradual but uneven increases in sea ice coverage, the yearly average Antarctic sea ice extents reached a record high of 12.8 × 106 km2 in 2014, followed by a decline so precipitous that they reached their lowest value in the 40-y 1979–2018 satellite multichannel passive-microwave record, 10.7 × 106 km2, in 2017. In contrast, it took the Arctic sea ice cover a full 3 decades to register a loss that great in yearly average ice extents. Still, when considering the 40-y record as a whole, the Antarctic sea ice continues to have a positive overall trend in yearly average ice extents, although at 11,300 ± 5,300 km2⋅y−1, this trend is only 50% of the trend for 1979–2014, before the precipitous decline. Four of the 5 sectors into which the Antarctic sea ice cover is divided all also have 40-y positive trends that are well reduced from their 2014–2017 values. The one anomalous sector in this regard, the Bellingshausen/Amundsen Seas, has a 40-y negative trend, with the yearly average ice extents decreasing overall in the first 3 decades, reaching a minimum in 2007, and exhibiting an overall upward trend since 2007 (i.e., reflecting a reversal in the opposite direction from the other 4 sectors and the Antarctic sea ice cover as a whole).

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Modelling the influence of snow accumulation and snow-ice formation on the seasonal cycle of the Antarctic sea-ice cover

Climate Dynamics ◽

10.1007/s003820050280 ◽

1999 ◽

Vol 15 (4) ◽

pp. 251-268 ◽

Cited By ~ 146

Author(s):

T. Fichefet ◽

M. A. Morales Maqueda

Keyword(s):

Sea Ice ◽

Seasonal Cycle ◽

Ice Cover ◽

Snow Accumulation ◽

Ice Formation ◽

Antarctic Sea Ice ◽

The Antarctic

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Interannual and regional variability of Southern Ocean snow on sea ice

Annals of Glaciology ◽

10.3189/172756406781811475 ◽

2006 ◽

Vol 44 ◽

pp. 53-57 ◽

Cited By ~ 11

Author(s):

Thorsten Markus ◽

Donald J. Cavalieri

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Snow Depth ◽

Critical Role ◽

Ice Cover ◽

Insulation Property ◽

Regional Variability ◽

Indirect Measure ◽

Antarctic Sea Ice ◽

The Antarctic

AbstractSnow depth on sea ice plays a critical role in the heat exchange between ocean and atmosphere because of its thermal insulation property. Furthermore, a heavy snow load on the relatively thin Southern Ocean sea-ice cover submerges the ice floes below sea level, causing snow-to-ice conversion. Snowfall is also an important freshwater source into the weakly stratified ocean. Snow-depth on sea-ice information can be used as an indirect measure of solid precipitation. Satellite passive microwave data are used to investigate the interannual and regional variability of the snow cover on sea ice. In this study we make use of 12 years (1992–2003) of Special Sensor Microwave/Imager (SSM/I) radiances to calculate average monthly snow depth on the Antarctic sea-ice cover. For the Antarctic sea-ice region as a whole, we find that September snow depth and sea-ice area are negatively correlated, which is not the case for individual regions. An analysis of the snow depth around Antarctica was undertaken. The results show an overall increase in snow depth for each of the five Antarctic sectors and the region as a whole, but only the Indian Ocean sector and the entire Southern Ocean show a statistically significant increase. There is a partial eastward propagation of maximum snow depths, which may be related to the Antarctic Circumpolar Wave. The overall trend and the variability of regional snow-depth distributions are also in agreement with cyclone density.

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Modelling global warming and Antarctic sea-ice changes over the past century

Annals of Glaciology ◽

10.3189/1998aog27-1-413-419 ◽

1998 ◽

Vol 27 ◽

pp. 413-419 ◽

Cited By ~ 4

Author(s):

Xingren Wu ◽

W.F. Budd

Keyword(s):

Sea Ice ◽

Surface Temperature ◽

Ice Cover ◽

Past Century ◽

The Past ◽

Antarctic Sea Ice ◽

Ice Concentration ◽

The Antarctic ◽

Global Surface ◽

Ice Model

An atmosphere–sea-ice model is used in combination with results from a coupled atmosphere–ocean–sea-ice model to examine the changes of the Antarctic sea-ice cover influenced by atmospheric circulation associated with the global sea-surface temperature (SST) changes alone over the past century. Using the current climatological SST of Reynolds for forcing, a reasonable seasonal simulation of the Antarctic sea-ice cover for the present climate (including ice concentration, thickness and coverage) is obtained. When global SST anomalies for the past century (derived from the coupled atmosphere–ocean–sea-ice model) are imposed, sea ice becomes more extensive, on the annual average, by 0.7-1.2° of latitude, more compact by about 5-7%, and thicker by 7-13 cm, than at present. These changes are similar to those simulated from changes in greenhouse gases using the coupled atmosphere–ocean–sea-ice model which gave corresponding changes of about 0.8° of latitude in extent, 6% in ice concentration and 12 cm in ice thickness. The simulated change in annual mean global surface temperature by the coupled atmosphere–ocean–sea-ice model was 0.7 Κ (0.6 Κ over the ocean including sea ice) which is similar to the observed change. Over the Antarctic the corresponding simulated change is 1.2 Κ which also appears compatible with observations.

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A spurious jump in the satellite record: is Antarctic sea ice really expanding?

The Cryosphere Discussions ◽

10.5194/tcd-8-273-2014 ◽

2014 ◽

Vol 8 (1) ◽

pp. 273-288 ◽

Cited By ~ 4

Author(s):

I. Eisenman ◽

W. N. Meier ◽

J. R. Norris

Keyword(s):

Sea Ice ◽

Ice Cover ◽

The Arctic ◽

Sea Ice Extent ◽

Physical Mechanisms ◽

Antarctic Sea Ice ◽

Ice Retreat ◽

Bootstrap Algorithm ◽

Sea Ice Retreat ◽

The Antarctic

Abstract. Recent estimates indicate that the Antarctic sea ice cover is expanding at a statistically significant rate with a magnitude one third as large as the rapid rate of sea ice retreat in the Arctic. However, during the mid-2000s, with several fewer years in the observational record, the trend in Antarctic sea ice extent was reported to be considerably smaller and statistically indistinguishable from zero. Here, we show that the increase in the reported trend occurred primarily due to the effect of a previously undocumented change in the way the satellite sea ice observations are processed for the widely-used Bootstrap algorithm dataset, rather than a physical increase in the rate of ice advance. Although our analysis does not definitively identify whether this undocumented change introduced an error or removed one, the resulting difference in the trends suggests that a substantial error exists in either the current dataset or the version that was used prior to the mid-2000s, and numerous studies that have relied on these observations should be reexamined to determine the sensitivity of their results to this change in the dataset. Furthermore, a number of recent studies have investigated physical mechanisms for the observed expansion of the Antarctic sea ice cover. The results of this analysis raise the possibility that this expansion may be a spurious artifact of an error in the satellite observations, and that the actual Antarctic sea ice cover may not be expanding at all.

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Inter-annual variations observed in spring and summer Antarctic sea ice extent in recent decade

MAUSAM ◽

10.54302/mausam.v62i4.381 ◽

2021 ◽

Vol 62 (4) ◽

pp. 633-640

Author(s):

SANDIP R.OZA ◽

R.K.K. SINGH ◽

ABHINAV SRIVASTAVA ◽

MIHIR K.DASH ◽

I.M.L. DAS ◽

...

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Large Scale ◽

Ross Sea ◽

Ice Cover ◽

Weddell Sea ◽

The Arctic ◽

Sea Ice Extent ◽

Antarctic Sea Ice ◽

The Antarctic

The growth and decay of sea ice are complex processes and have important feedback onto the oceanic and atmospheric circulation. In the Antarctic, sea ice variability significantly affects the primary productivity in the Southern Ocean and thereby negatively influences the performance and survival of species in polar ecosystem. In present days, the awareness on the sea ice variability in the Antarctic is not as matured as it is for the Arctic region. The present paper focuses on the inter-annual trends (1999-2009) observed in the monthly fractional sea ice cover in the Antarctic at 1 × 1 degree level, for the November and February months, derived from QuikSCAT scatterometer data. OSCAT scatterometer data from India’s Oceansat-2 satellite were used to asses the sea ice extent (SIE) observed in the month of November 2009 and February 2010 and its deviation from climatic maximum (1979-2002) sea ice extent (CMSIE). Large differences were observed between SIE and CMSIE, however, trend results show that it is due to the high inter-annual variability in sea ice cover. Spatial distribution of trends show the existence of positive and negative trends in the parts of Western Pacific Ocean, Ross Sea, Amundsen and Bellingshausen Seas (ABS), Weddell Sea and Indian ocean sector of southern ocean. Sea ice trends are compared with long-term SST trends (1982-2009) observed in the austral summer month of February. Large-scale cooling trend observed around Ross Sea and warming trend in ABS sector are the distinct outcome of the study.

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The Antarctic sea ice cover from ICESat-2 and CryoSat-2: freeboard, snow depth and ice thickness

10.5194/tc-2020-145-rc2 ◽

2020 ◽

Keyword(s):

Sea Ice ◽

Snow Depth ◽

Ice Cover ◽

Ice Thickness ◽

Antarctic Sea Ice ◽

The Antarctic

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The Antarctic sea ice cover from ICESat-2 and CryoSat-2: freeboard, snow depth and ice thickness

10.5194/tc-2020-145 ◽

2020 ◽

Author(s):

Sahra Kacimi ◽

Ron Kwok

Keyword(s):

Sea Ice ◽

Snow Depth ◽

Basal Layer ◽

Ice Cover ◽

Ice Thickness ◽

Data Set ◽

Amundsen Sea ◽

Ice Volume ◽

Antarctic Sea Ice ◽

The Antarctic

Abstract. We offer a view of the Antarctic sea ice cover from lidar (ICESat-2) and radar (CryoSat-2) altimetry, with retrievals of freeboards, snow depth, and ice volume that span an 8-month winter between April 2019 and November 2019. Snow depths are from freeboard differences. The multiyear ice in the West Weddell sector stands out with a mean sector thickness > 2 m. Thinnest ice is found near polynyas (Ross Sea and Ronne) where new ice areas are exported seaward and entrained in the surrounding ice cover. For all months, the results suggest that ~ 60–70 % of the total freeboard is comprised of snow. The remarkable response of the ice cover to mechanical convergence in the coastal Amundsen Sea, associated with onshore winds, was captured in the correlated increase in local freeboards and thickness. While the spatial patterns in the freeboard, snow depth, and thickness composites are as expected, the observed seasonality in these variables is surprisingly weak likely attributable to competing processes (snowfall, snow redistribution, snow-ice formation, ice deformation, basal growth/melt) that contribute to uncorrelated changes in the total and radar freeboards. Broadly, evidence points to biases in CryoSat-2 freeboards of at least a few centimeters from high salinity snow (> 10 psu) in the basal layer resulting in lower/higher snow depth/ice thickness retrievals although the extent of these areas cannot be established in the current data set. Adjusting CryoSat-2 freeboards by 3/6 cm gives a circumpolar ice volume of 14,700/12,400 km3 in October, for an average thickness of ~ 1.09/0.93 m. Validation of Antarctic sea ice parameters remains a challenge, there are no seasonally and regionally diverse data sets that could be used to assess these large-scale satellite retrievals.

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