Sensitivity of Antarctic sea ice to the Southern Annular Mode in coupled climate models

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 Regime Shift in Seasonal Total Antarctic Sea Ice Extent in the 20th Century

10.21203/rs.3.rs-828060/v1 ◽

2021 ◽

Author(s):

Ryan Fogt ◽

Amanda Sleinkofer ◽

Marilyn Raphael ◽

Mark Handcock

Keyword(s):

Sea Ice ◽

20Th Century ◽

Climate Models ◽

Historical Context ◽

The Arctic ◽

Sea Ice Extent ◽

Antarctic Sea Ice ◽

Coupled Climate Models ◽

High Degree ◽

The Antarctic

Abstract In stark contrast to the Arctic, there have been statistically significant positive trends in total Antarctic sea ice extent since 1979, despite a sudden decline in sea ice in 2016(1–5) and increasing greenhouse gas concentrations. Attributing Antarctic sea ice trends is complicated by the fact that most coupled climate models show negative trends in sea ice extent since 1979, opposite of that observed(6–8). Additionally, the short record of sea ice extent (beginning in 1979), coupled with the high degree of interannual variability, make the record too short to fully understand the historical context of these recent changes(9). Here we show, using new robust observation-based reconstructions, that 1) these observed recent increases in Antarctic sea ice extent are unique in the context of the 20th century and 2) the observed trends are juxtaposed against statistically significant decreases in sea ice extent throughout much of the early and middle 20th century. These reconstructions are the first to provide reliable estimates of total sea ice extent surrounding the continent; previous proxy-based reconstructions are limited(10). Importantly, the reconstructions continue to show the high degree of interannual Antarctic sea ice extent variability that is marked with frequent sudden changes, such as observed in 2016, which stress the importance of a longer historical context when assessing and attributing observed trends in Antarctic climate(9). Our reconstructions are skillful enough to be used in climate models to allow better understanding of the interconnected nature of the Antarctic climate system and to improve predictions of the future state of Antarctic climate.

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Interactions between Antarctic sea ice and large-scale atmospheric modes in CMIP5 models

10.5194/tc-2016-200 ◽

2016 ◽

Author(s):

Serena Schroeter ◽

Will Hobbs ◽

Nathaniel L. Bindoff

Keyword(s):

Sea Ice ◽

Large Scale ◽

Coupled Model ◽

Southern Annular Mode ◽

Cmip5 Models ◽

Atmospheric Variability ◽

Annular Mode ◽

Antarctic Sea Ice ◽

Ice Retreat ◽

Sea Ice Retreat

Abstract. The response of Antarctic sea ice to large-scale patterns of atmospheric variability varies according to sea ice sector and season. In this study, interannual atmosphere-sea ice interactions were explored using observation-based data and compared with simulated interactions by models in the Coupled Model Intercomparison Project Phase 5. Simulated relationships between atmospheric variability and sea ice variability generally reproduced the observed relationships, though more closely during the season of sea ice advance than the season of sea ice retreat. Atmospheric influence on sea ice is known to be strongest during its advance, with the ocean emerging as a dominant driver of sea ice retreat; therefore, while it appears that models are able to capture the dominance of the atmosphere during advance, simulations of ocean-atmosphere-sea ice interactions during retreat require further investigation. A large proportion of model ensemble members overestimated the relative importance of the Southern Annular Mode compared with other modes on high southern latitude climate, while the influence of tropical forcing was underestimated. This result emerged particularly strongly during the season of sea ice retreat. The amplified zonal patterns of the Southern Annular Mode in many models and its exaggerated influence on sea ice overwhelm the comparatively underestimated meridional influence, suggesting that simulated sea ice variability would become more zonally symmetric as a result. Across the seasons of sea ice advance and retreat, 3 of the 5 sectors did not reveal a strong relationship with a pattern of large-scale atmospheric variability in one or both seasons, indicating that sea ice in these sectors may be influenced more strongly by atmospheric variability unexplained by the major atmospheric modes, or by heat exchange in the ocean.

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Aspects of intraseasonal variability of Antarctic sea ice in austral winter related to ENSO and SAM events

Journal of Glaciology ◽

10.1017/jog.2017.49 ◽

2017 ◽

Vol 63 (241) ◽

pp. 838-846 ◽

Cited By ~ 3

Author(s):

KENJI BABA ◽

JAMES RENWICK

Keyword(s):

Sea Ice ◽

El Nino ◽

Intraseasonal Variability ◽

Southern Annular Mode ◽

Wave Number ◽

Austral Winter ◽

Sea Ice Concentration ◽

Annular Mode ◽

Antarctic Sea Ice ◽

Ice Concentration

ABSTRACTWe performed an Empirical Orthogonal Function (EOF) analysis to assess the intraseasonal variability of 5–60 day band-pass filtered Antarctic sea-ice concentration in austral winter using a 20-year daily dataset from 1995 to 2014. Zonal wave number 3 dominated in the Antarctic, especially so across the west Antarctic. Results showed the coexistence of stationary and propagating wave components. A spectral analysis of the first two principal components (PCs) showed a similar structure for periods up to 15 days but generally more power in PC1 at longer periods. Regression analysis upon atmospheric fields using the first two PCs of sea-ice concentration showed a coherent wave number 3 pattern. The spatial phase delay between the sea-ice and mean sea-level pressure patterns suggests that meridional flow and associated temperature advection are important for modulating the sea-ice field. EOF analyses carried out separately for El Niño, La Niña and neutral years, and for Southern Annular Mode positive, negative and neutral periods, suggest that the spatial patterns of wave number 3 shift between subsets. The results also indicate that El Niño-Southern Oscillation and Southern Annular Mode affect stationary wave interactions between sea-ice and atmospheric fields on intraseasonal timescales.

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Climate Impacts of the Southern Annular Mode Simulated by the CMIP3 Models

Journal of Climate ◽

10.1175/2009jcli2788.1 ◽

2009 ◽

Vol 22 (13) ◽

pp. 3751-3768 ◽

Cited By ~ 29

Author(s):

Alexey Yu Karpechko ◽

Nathan P. Gillett ◽

Gareth J. Marshall ◽

James A. Screen

Keyword(s):

Sea Ice ◽

Climate Models ◽

Temperature Response ◽

Coupled Model ◽

Surface Air Temperature ◽

Southern Annular Mode ◽

Climate Impacts ◽

Sea Ice Concentration ◽

Annular Mode ◽

Simulated Precipitation

Abstract The southern annular mode (SAM) has a well-established impact on climate in the Southern Hemisphere. The strongest response in surface air temperature (SAT) is observed in the Antarctic, but the SAM’s area of influence extends much farther, with statistically significant effects on temperature and precipitation being detected as far north as 20°S. Here the authors quantify the ability of the Coupled Model Intercomparison Project, phase 3 (CMIP3) coupled climate models to simulate the observed SAT, total precipitation, sea surface temperature (SST), and sea ice concentration responses to the SAM. The models are able to simulate the spatial pattern of response in SAT reasonably well; however, all models underestimate the magnitude of the response over Antarctica, both at the surface and in the free troposphere. This underestimation of the temperature response has implications for prediction of the future temperature changes associated with expected changes in the SAM. The models possess reasonable skill in simulating patterns of precipitation and SST response; however, some considerable regional deviations exist. The simulated precipitation and SST responses are less constrained by the observations than the SAT response, particularly in magnitude, as significant discrepancies are detected between the responses in the reference datasets. The largest problems are identified in simulating the sea ice response to the SAM, with some models even simulating a response that is negatively correlated with that observed.

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Climate links and recent extremes in antarctic sea ice, high-latitude cyclones, Southern Annular Mode and ENSO

Climate Dynamics ◽

10.1007/s00382-011-1044-y ◽

2011 ◽

Vol 38 (1-2) ◽

pp. 57-73 ◽

Cited By ~ 73

Author(s):

Alexandre Bernardes Pezza ◽

Harun A. Rashid ◽

Ian Simmonds

Keyword(s):

Sea Ice ◽

High Latitude ◽

Southern Annular Mode ◽

Annular Mode ◽

Antarctic Sea Ice

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Modulation of the Seasonal Cycle of Antarctic Sea Ice Extent Related to the Southern Annular Mode

Geophysical Research Letters ◽

10.1002/2017gl074319 ◽

2017 ◽

Vol 44 (19) ◽

pp. 9761-9768 ◽

Cited By ~ 25

Author(s):

Edward W. Doddridge ◽

John Marshall

Keyword(s):

Sea Ice ◽

Seasonal Cycle ◽

Southern Annular Mode ◽

Sea Ice Extent ◽

Annular Mode ◽

Antarctic Sea Ice

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The Influence of Sea Ice Dynamics on the Climate Sensitivity and Memory to Increased Antarctic Sea Ice

Journal of Climate ◽

10.1175/jcli-d-14-00748.1 ◽

2015 ◽

Vol 28 (24) ◽

pp. 9642-9668 ◽

Cited By ~ 5

Author(s):

Claudia K. Parise ◽

Luciano P. Pezzi ◽

Kevin I. Hodges ◽

Flavio Justino

Keyword(s):

Sea Ice ◽

Climate Sensitivity ◽

Southern Annular Mode ◽

Fast Response ◽

Heat Fluxes ◽

Positive Phase ◽

Ice Dynamics ◽

Antarctic Sea Ice ◽

Current Climate ◽

Subsurface Layers

Abstract The study analyzes the sensitivity and memory of the Southern Hemisphere coupled climate system to increased Antarctic sea ice (ASI), taking into account the persistence of the sea ice maxima in the current climate. The mechanisms involved in restoring the climate balance under two sets of experiments, which differ in regard to their sea ice models, are discussed. The experiments are perturbed with extremes of ASI and integrated for 10 yr in a large 30-member ensemble. The results show that an ASI maximum is able to persist for ~4 yr in the current climate, followed by a negative sea ice phase. The sea ice insulating effect during the positive phase reduces heat fluxes south of 60°S, while at the same time these are intensified at the sea ice edge. The increased air stability over the sea ice field strengthens the polar cell while the baroclinicity increases at midlatitudes. The mean sea level pressure is reduced (increased) over high latitudes (midlatitudes), typical of the southern annular mode (SAM) positive phase. The Southern Ocean (SO) becomes colder and fresher as the sea ice melts mainly through sea ice lateral melting, the consequence of which is an increase in the ocean stability by buoyancy and mixing changes. The climate sensitivity is triggered by the sea ice insulating process and the resulting freshwater pulse (fast response), while the climate equilibrium is restored by the heat stored in the SO subsurface layers (long response). It is concluded that the time needed for the ASI anomaly to be dissipated and/or melted is shortened by the sea ice dynamical processes.

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Sea Ice in Coupled Climate Models

Encyclopedia of Ocean Sciences ◽

10.1016/b978-0-12-409548-9.11531-3 ◽

2019 ◽

pp. 200-207

Author(s):

Dirk Notz

Keyword(s):

Sea Ice ◽

Climate Models ◽

Coupled Climate Models

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East Antarctic sea ice: observations and modelling

Annals of Glaciology ◽

10.3189/1998aog27-1-427-432 ◽

1998 ◽

Vol 27 ◽

pp. 427-432 ◽

Cited By ~ 5

Author(s):

Anthony P. Worby ◽

Xingren Wu

Keyword(s):

Sea Ice ◽

Climate Models ◽

Numerical Models ◽

Global Climate ◽

Thickness Distribution ◽

Ice Thickness ◽

Antarctic Sea Ice ◽

Pack Ice ◽

Concentration Sensitivity ◽

Sensitivity Studies

The importance of monitoring sea ice for studies of global climate has been well noted for several decades. Observations have shown that sea ice exhibits large seasonal variability in extent, concentration and thickness. These changes have a significant impact on climate, and the potential nature of many of these connections has been revealed in studies with numerical models. An accurate representation of the sea-ice distribution (including ice extent, concentration and thickness) in climate models is therefore important for modelling global climate change. This work presents an overview of the observed sea-ice characteristics in the East Antarctic pack ice (60-150° E) and outlines possible improvements to the simulation of sea ice over this region by modifying the ice-thickness parameterisation in a coupled sea-ice-atmosphere model, using observational data of ice thickness and concentration. Sensitivity studies indicate that the simulation of East Antarctic sea ice can be improved by modifying both the “lead parameterisation” and “rafting scheme” to be ice-thickness dependent. The modelled results are currently out of phase with the observed data, and the addition of a multilevel ice-thickness distribution would improve the simulation significantly.

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