scholarly journals Review of The Cryosphere Discussion submission tc-2020-71 ‘Evaluation of Sea-Ice Thickness from four reanalyses in the Antarctic Weddell Sea’

2020 ◽  
Author(s):  
Daniel Price
Keyword(s):  
Sea Ice ◽  
Weddell Sea ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
The Antarctic

scholarly journals A comparison between Envisat and ICESat sea ice thickness in the Antarctic

2020 ◽  
Author(s):  
Jinfei Wang ◽  
Chao Min ◽  
Robert Ricker ◽  
Qinghua Yang ◽  
Qian Shi ◽  
...  
Keyword(s):  
Sea Ice ◽  
European Space Agency ◽  
Weddell Sea ◽  
Ice Thickness ◽  
Radar Altimeter ◽  
Average Deviation ◽  
Absolute Deviation ◽  
Sea Ice Thickness ◽  
Antarctic Sea Ice ◽  
The Antarctic

Abstract. The crucial role that Antarctic sea ice plays in the global climate system is strongly linked to its thickness. While in situ observations are too sparse in the Antarctic to determine long-term trends of the Antarctic sea ice thickness on a global scale, satellite radar altimetry data can be applied with a promising prospect. A newly released Envisat-derived product from the European Space Agency Sea Ice Climate Change Initiative (ESA SICCI), including sea ice freeboard and sea ice thickness, covers the entire Antarctic year-round from 2002 to 2012. In this study, the SICCI Envisat sea ice thickness in the Antarctic is firstly compared with a conceptually new proposed ICESat ice thickness that has been derived from an algorithm employing modified ice density. Both data sets have been validated with the Weddell Sea upward looking sonar measurements (ULS), indicating that ICESat agrees better with field observations. The inter-comparisons are conducted for three seasons except winter based on the ICESat operating periods. According to the results, the deviations between Envisat and ICESat sea ice thickness are different considering different seasons, years and regions. More specifically, the smallest average deviation between Envisat and ICESat sea ice thickness exists in spring by −0.03 m while larger deviations exist in summer and autumn by 0.86 m and 0.62 m, respectively. Although the smallest absolute deviation occurs in spring 2005 by 0.02 m, the largest correlation coefficient appears in autumn 2004 by 0.77. The largest positive deviation occurs in the western Weddell Sea by 1.03 m in summer while the largest negative deviation occurs in the Eastern Antarctic by −0.25 m in spring. Potential reasons for those deviations mainly deduce from the limitations of Envisat radar altimeter affected by the weather conditions and the surface roughness as well as the different retrieval algorithms. The better performance in spring of Envisat has a potential relation with relative humidity.

scholarly journals Influence of the Southern Annular Mode on the sea ice-ocean system: the role of the thermal and mechanical forcing

Ocean Science ◽  
2005 ◽  
Vol 1 (3) ◽  
pp. 145-157 ◽  
Author(s):  
W. Lefebvre ◽  
H. Goosse
Keyword(s):  
Sea Ice ◽  
Air Temperature ◽  
Wind Stress ◽  
Southern Annular Mode ◽  
Weddell Sea ◽  
The Other ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Annular Mode ◽  
The Antarctic

Abstract. The global sea ice-ocean model ORCA2-LIM is used to investigate the impact of the thermal and mechanical forcing associated with the Southern Annular Mode (SAM) on the Antarctic sea ice-ocean system. The model is driven by idealized forcings based on regressions between the wind stress and the air temperature at one hand and the SAM index the other hand. The wind-stress component strongly affects the overall patterns of the ocean circulation with a northward surface drift, a downwelling at about 45° S and an upwelling in the vicinity of the Antarctic continent when the SAM is positive. On the other hand, the thermal forcing has a negligible effect on the ocean currents. For sea ice, both the wind-stress (mechanical) and the air temperature (thermal) components have a significant impact. The mechanical part induces a decrease of the sea ice thickness close to the continent and a sharp decrease of the mean sea ice thickness in the Weddell sector. In general, the sea ice area also diminishes, with a maximum decrease in the Weddell Sea. On the contrary, the thermal part tends to increase the ice concentration in all sectors except in the Weddell Sea, where the ice area shrinks. This thermal effect is the strongest in autumn and in winter due to the larger temperature differences associated with the SAM during these seasons. The sum of the thermal and mechaninal effects gives a dipole response of sea ice to the SAM, with a decrease of the ice area in the Weddell Sea and around the Antarctic Peninsula and an increase in the Ross and Amundsen Seas during high SAM years. This is in good agreement with the observed response of the ice cover to the SAM.

Improved sea-ice prediction in the Weddell Sea using sea-ice thickness initialization

2021 ◽  
Author(s):  
Yushi Morioka ◽  
Doroteaciro Iovino ◽  
Andrea Cipollone ◽  
Simona Masina ◽  
Swadhin Behera
Keyword(s):  
Sea Ice ◽  
General Circulation ◽  
Climate Models ◽  
Circulation Model ◽  
Weddell Sea ◽  
Ice Thickness ◽  
Austral Spring ◽  
Sea Ice Concentration ◽  
Sea Ice Thickness ◽  
The Antarctic

<p>Skillful sea-ice prediction in the Antarctic Ocean remains a big challenge due to paucity of sea-ice observations and insufficient representation of sea-ice processes in climate models. This study demonstrates that the Antarctic sea-ice concentration (SIC) prediction is significantly improved using a coupled general circulation model (SINTEX-F2) in which the model’s SIC and sea-ice thickness (SIT) are initialized with the ocean/sea-ice reanalysis product (C-GLORSv7). It is found that the wintertime SIT initialization adds positive values to the prediction skills of the summertime SIC, most effectively in the Weddell Sea where the SIT climatology and variability are the largest among the Antarctic Seas. Examination of the SIT balance during low sea-ice years of the Weddell Sea shows that negative SIT anomalies initialized in June retain the memory throughout austral winter (July-September) owing to horizontal advection of the SIT anomalies by sea-ice velocities. The negative SIT anomalies continue to develop in austral spring (October-December) owing to more incoming solar radiation via ice-albedo feedback and the associated warming of mixed layer. This results in further sea-ice decrease during austral summer (January-March). Concomitantly, the model reasonably reproduces atmospheric circulation anomalies in the Amundsen-Bellingshausen Seas as well as the Weddell Sea during the development of the negative sea-ice anomalies. These results provide solid evidence that the wintertime SIT initialization benefits skillful summertime sea-ice prediction in the Antarctic Seas.</p>

scholarly journals Influence of the Southern Annular Mode on the sea ice-ocean system: the role of the thermal and mechanical forcing

2005 ◽  
Vol 2 (3) ◽  
pp. 299-329 ◽  
Author(s):  
W. Lefebvre ◽  
H. Goosse
Keyword(s):  
Sea Ice ◽  
Air Temperature ◽  
Wind Stress ◽  
Southern Annular Mode ◽  
Weddell Sea ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Annular Mode ◽  
Mechanical Forcing ◽  
The Antarctic

Abstract. The global sea ice-ocean model ORCA2-LIM is used to investigate the impact of the thermal and mechanical forcing associated to the Southern Annular Mode (SAM) on the Antarctic sea ice-ocean system. To do so, the model is driven by idealized forcings based on regressions of the wind stress and the air temperature to SAM. The wind-stress component strongly affects the overall patterns of the ocean circulation with a northward surface drift, a downwelling at about 45° S and an upwelling in the vicinity of the Antarctic continent when SAM is positive. On the other hand, the thermal forcing has a negligible effect on the ocean currents. For sea ice, both the wind-stress (mechanical) and the air temperature (thermal) components have a significant impact. The mechanical part induces a decrease of the sea ice thickness close to the continent and a sharp decrease of the mean sea ice thickness in the Weddell sector. In general, the sea ice area also diminishes, with a maximum decrease in the Weddell Sea. On the contrary, the thermal part tends to increase the ice concentration in all sectors except in the Weddell Sea, where the ice area shrinks. This thermal effect is the strongest in autumn and in winter due to the larger temperature differences associated with SAM during these seasons. The sum of the thermal and mechaninal effects gives a dipole response of sea ice to the SAM, with a decrease of the ice area in the Weddell Sea and around the Antarctic Peninsula and an increase in the Ross and Amundsen Seas during high SAM years. This is in good agreement with the observed response of the ice cover to SAM.

scholarly journals Evaluation of Sea-Ice Thickness from four reanalyses in the Antarctic Weddell Sea

2020 ◽  
Author(s):  
Qian Shi ◽  
Qinghua Yang ◽  
Longjiang Mu ◽  
Jinfei Wang ◽  
François Massonnet ◽  
...  
Keyword(s):  
Sea Ice ◽  
Thickness Distribution ◽  
Weddell Sea ◽  
Ocean Modeling ◽  
Ice Thickness ◽  
First Year ◽  
Coupled Models ◽  
Sea Ice Thickness ◽  
The Antarctic

Abstract. Ocean-sea ice coupled models constrained by varied observations provide different ice thickness estimates in the Antarctic. We evaluate contemporary monthly ice thickness from four reanalyses in the Weddell Sea, the German contribution of the Estimating the Circulation and Climate of the Ocean project, Version 2 (GECCO2), the Southern Ocean State Estimate (SOSE), the Nucleus for European Modelling of the Ocean (NEMO) based ocean-ice model (called NEMO-EnKF), and the Global Ice-Ocean Modeling and Assimilation System (GIOMAS), and with reference observations from ICESat-1, Envisat, upward looking sonars and visual ship-based sea-ice observations. Compared with ICESat-1 altimetry and in situ observations, all reanalyses underestimate ice thickness near the coast of the western Weddell Sea, even though ICESat-1 and visual observations may be biased low. GECCO2 and NEMO-EnKF can well reproduce the seasonal variation of first-year ice thickness in the eastern Weddell Sea. In contrast, GIOMAS ice thickness performs best in the central Weddell Sea, while SOSE ice thickness agrees most with the observations in the southern coast of the Weddell Sea. In addition, only NEMO-EnKF can reproduce the seasonal spatial evolution of ice thickness distribution well, characterized by the thick ice shifting from the southwestern and western Weddell Sea in summer to the western and northwestern Weddell Sea in spring. We infer that the thick ice distribution is correlated with its better simulation of northward ice motion in the western Weddell Sea. These results demonstrate the possibilities and limitations of using current sea-ice reanalysis for understanding the recent variability of sea-ice volume in the Antarctic.

scholarly journals Evaluation of sea-ice thickness from four reanalyses in the Antarctic Weddell Sea

2021 ◽  
Vol 15 (1) ◽  
pp. 31-47
Author(s):  
Qian Shi ◽  
Qinghua Yang ◽  
Longjiang Mu ◽  
Jinfei Wang ◽  
François Massonnet ◽  
...  
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Weddell Sea ◽  
Ocean Modeling ◽  
Ice Thickness ◽  
Coupled Models ◽  
Sea Ice Thickness ◽  
In Situ Observations ◽  
The Antarctic

Abstract. Ocean–sea-ice coupled models constrained by various observations provide different ice thickness estimates in the Antarctic. We evaluate contemporary monthly ice thickness from four reanalyses in the Weddell Sea: the German contribution of the project Estimating the Circulation and Climate of the Ocean Version 2 (GECCO2), the Southern Ocean State Estimate (SOSE), the Ensemble Kalman Filter system based on the Nucleus for European Modelling of the Ocean (NEMO-EnKF) and the Global Ice–Ocean Modeling and Assimilation System (GIOMAS). The evaluation is performed against reference satellite and in situ observations from ICESat-1, Envisat, upward-looking sonars and visual ship-based sea-ice observations. Compared with ICESat-1, NEMO-EnKF has the highest correlation coefficient (CC) of 0.54 and lowest root mean square error (RMSE) of 0.44 m. Compared with in situ observations, SOSE has the highest CC of 0.77 and lowest RMSE of 0.72 m. All reanalyses underestimate ice thickness near the coast of the western Weddell Sea with respect to ICESat-1 and in situ observations even though these observational estimates may be biased low. GECCO2 and NEMO-EnKF reproduce the seasonal variation in first-year ice thickness reasonably well in the eastern Weddell Sea. In contrast, GIOMAS ice thickness performs best in the central Weddell Sea, while SOSE ice thickness agrees most with the observations from the southern coast of the Weddell Sea. In addition, only NEMO-EnKF can reproduce the seasonal evolution of the large-scale spatial distribution of ice thickness, characterized by the thick ice shifting from the southwestern and western Weddell Sea in summer to the western and northwestern Weddell Sea in spring. We infer that the thick ice distribution is correlated with its better simulation of northward ice motion in the western Weddell Sea. These results demonstrate the possibilities and limitations of using current sea-ice reanalysis for understanding the recent variability of sea-ice volume in the Antarctic.

scholarly journals A comparison between Envisat and ICESat sea ice thickness in the Antarctic

2021 ◽  
Author(s):  
Jinfei Wang ◽  
Chao Min ◽  
Robert Ricker ◽  
Qian Shi ◽  
Bo Han ◽  
...  
Keyword(s):  
Sea Ice ◽  
Snow Depth ◽  
Spatial Variations ◽  
Weddell Sea ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Temporal And Spatial Variations ◽  
Antarctic Sea Ice ◽  
Temporal And Spatial ◽  
The Antarctic

Abstract. The crucial role that Antarctic sea ice plays in the global climate system is strongly linked to its thickness. While field observations are too sparse in the Antarctic to determine long-term trends of the Antarctic sea ice thickness (SIT) on a hemispheric scale, satellite radar altimetry data can be applied with a promising prospect. European Space Agency Climate Change Initiative – Sea Ice Project (ESA SICCI) includes sea ice freeboard and sea ice thickness derived from Envisat, covering the entire Antarctic year-round from 2002 to 2012. In this study, the SICCI Envisat SIT in the Antarctic is first compared with a conceptually new ICESat SIT product retrieved from an algorithm employing modified ice density. Both data sets are compared to SIT estimates from upward-looking sonar (ULS) in the Weddell Sea, showing mean differences (MD) and standard deviations (SD) of 1.29 (0.65) m for Envisat-ULS, while we find 1.11 (0.81) m for ICESat-ULS, respectively. The inter-comparisons are conducted for three seasons except winter, based on the ICESat operating periods. According to the results, the differences between Envisat and ICESat SIT reveal significant temporal and spatial variations. More specifically, the smallest seasonal SIT MD (with SD shown in brackets) of 0.00 m (0.39 m) for Envisat-ICESat for the entire Antarctic is found in spring (October–November) while larger MD of 0.52 m (0.68 m) and 0.57 m (0.45 m) exist in summer (February–March) and autumn (May–June), respectively. It is also shown that from autumn to spring, mean Envisat SIT decreases while mean ICESat SIT increases. Our findings suggest that overestimation of Envisat sea ice freeboard, potentially caused by radar backscatter originating from inside the snow layer, primarily accounts for the differences between Envisat and ICESat SIT in summer and autumn, while the uncertainties of snow depth product are not the dominant cause of the differences.To get a better understanding of the characteristics of the Envisat-derived sea ice thickness product, we firstly conduct a comprehensive comparison between Envisat and ICESat-1 sea ice thickness. Their differences reveal significant temporal and spatial variations. Our findings suggest that overestimation of Envisat sea ice freeboard primarily accounts for the differences in summer and autumn, while the uncertainties of snow depth product are not the dominant cause of the differences. 

scholarly journals Summertime sea-ice prediction in the Weddell Sea improved by sea-ice thickness initialization

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yushi Morioka ◽  
Doroteaciro Iovino ◽  
Andrea Cipollone ◽  
Simona Masina ◽  
Swadhin K. Behera
Keyword(s):  
Sea Ice ◽  
General Circulation ◽  
Climate Models ◽  
Circulation Model ◽  
Weddell Sea ◽  
Ice Thickness ◽  
Austral Spring ◽  
Sea Ice Concentration ◽  
Sea Ice Thickness ◽  
The Antarctic

AbstractSkillful sea-ice prediction in the Antarctic Ocean remains a big challenge due to paucity of sea-ice observations and insufficient representation of sea-ice processes in climate models. Using a coupled general circulation model, this study demonstrates skillful prediction of the summertime sea-ice concentration (SIC) in the Weddell Sea with wintertime SIC and sea-ice thickness (SIT) initializations. During low sea-ice years of the Weddell Sea, negative SIT anomalies initialized in June retain the memory throughout austral winter owing to horizontal advection of the SIT anomalies. The SIT anomalies continue to develop in austral spring owing to more incoming solar radiation and the associated warming of mixed layer, contributing to further sea-ice decrease during late austral summer-early autumn. Concomitantly, the model reasonably reproduces atmospheric circulation anomalies during austral spring in the Amundsen-Bellingshausen Seas besides the Weddell Sea. These results provide evidence that the wintertime SIT initialization benefits skillful summertime sea-ice prediction in the Antarctic Seas.

scholarly journals ICESat observations of seasonal and interannual variations of sea-ice freeboard and estimated thickness in the Weddell Sea, Antarctica (2003–2009)

2011 ◽  
Vol 52 (57) ◽  
pp. 43-51 ◽  
Author(s):  
Donghui Yi ◽  
H. Jay Zwally ◽  
John W. Robbins
Keyword(s):  
Sea Ice ◽  
Weddell Sea ◽  
Ice Thickness ◽  
Sea Ice Extent ◽  
Sea Ice Thickness ◽  
Earth Observing System ◽  
Pack Ice ◽  
Snow Water ◽  
The Mean ◽  
Seasonal And Interannual Variations

AbstractSea-ice freeboard heights for 17 ICESat campaign periods from 2003 to 2009 are derived from ICESat data. Freeboard is combined with snow depth from Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) data and nominal densities of snow, water and sea ice, to estimate sea-ice thickness. Sea-ice freeboard and thickness distributions show clear seasonal variations that reflect the yearly cycle of growth and decay of the Weddell Sea (Antarctica) pack ice. During October–November, sea ice grows to its seasonal maximum both in area and thickness; the mean freeboards are 0.33–0.41m and the mean thicknesses are 2.10–2.59 m. During February–March, thinner sea ice melts away and the sea-ice pack is mainly distributed in the west Weddell Sea; the mean freeboards are 0.35–0.46m and the mean thicknesses are 1.48–1.94 m. During May–June, the mean freeboards and thicknesses are 0.26–0.29m and 1.32–1.37 m, respectively. the 6 year trends in sea-ice extent and volume are (0.023±0.051)×106 km2 a–1 (0.45% a–1) and (0.007±0.092)×103 km3 a–1 (0.08% a–1); however, the large standard deviations indicate that these positive trends are not statistically significant.

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