Sensitivity of the Antarctic sea ice distribution to its advection in a general circulation model

1997 ◽  
Vol 9 (4) ◽  
pp. 445-455 ◽  
Author(s):  
Xingren Wu ◽  
W.F. Budd ◽  
Ian Simmonds
Keyword(s):  
Sea Ice ◽  
Seasonal Cycle ◽  
General Circulation ◽  
Circulation Model ◽  
Coupled System ◽  
Atmospheric Conditions ◽  
Atmospheric Forcing ◽  
Antarctic Sea Ice ◽  
The Antarctic ◽  
Ice Model

A dynamic-thermodynamic sea ice model is used and coupled with an atmospheric general circulation model to simulate the seasonal cycle of the global sea ice distribution. We have run the coupled system and obtain a creditable seasonal simulation of the Antarctic sea ice. To understand the role of ice advection on the seasonal cycle of Antarctic sea ice in the coupled system, results from the thermodynamiconly (T) sea ice model have been compared with those from the dynamic thermodynamic (DT) sea ice model. The seasonal cycle of sea ice differs between the two models. When ice motion is eliminated sea ice becomes more compact and thinner, and sea ice is more extensive in summer. A number of previous studies have examined the effect of ice dynamics on sea ice simulations with prescribed atmospheric conditions. Here experiments have been performed with a fully coupled atmosphere sea ice system and also using prescribed daily atmospheric forcing and monthly mean atmospheric forcing, to examine the differences of the sensitivity of the ice advection between the coupled and forcing models. Similar differences have been observed between DT and T in the forcing models but the magnitude is smaller than in the fully coupled model, and with monthly mean atmospheric forcing the difference is least. These differences highlight the importance of the inclusion of ice advection when undertaking studies using a fully interactive atmosphere sea ice model, or using prescribed daily/monthly atmospheric conditions to force a sea ice model for the Antarctic.

scholarly journals On the discretization of the ice thickness distribution in the NEMO3.6-LIM3 global ocean–sea ice model

2019 ◽  
Vol 12 (8) ◽  
pp. 3745-3758 ◽  
Author(s):  
François Massonnet ◽  
Antoine Barthélemy ◽  
Koffi Worou ◽  
Thierry Fichefet ◽  
Martin Vancoppenolle ◽  
...  
Keyword(s):  
Sea Ice ◽  
General Circulation ◽  
Large Scale ◽  
Thickness Distribution ◽  
Circulation Model ◽  
Grid Cell ◽  
The Arctic ◽  
Global Ocean ◽  
Ice Thickness ◽  
Ice Model

Abstract. The ice thickness distribution (ITD) is one of the core constituents of modern sea ice models. The ITD accounts for the unresolved spatial variability of sea ice thickness within each model grid cell. While there is a general consensus on the added physical realism brought by the ITD, how to discretize it remains an open question. Here, we use the ocean–sea ice general circulation model, Nucleus for European Modelling of the Ocean (NEMO) version 3.6 and Louvain-la-Neuve sea Ice Model (LIM) version 3 (NEMO3.6-LIM3), forced by atmospheric reanalyses to test how the ITD discretization (number of ice thickness categories, positions of the category boundaries) impacts the simulated mean Arctic and Antarctic sea ice states. We find that winter ice volumes in both hemispheres increase with the number of categories and attribute that increase to a net enhancement of basal ice growth rates. The range of simulated mean winter volumes in the various experiments amounts to ∼30 % and ∼10 % of the reference values (run with five categories) in the Arctic and Antarctic, respectively. This suggests that the way the ITD is discretized has a significant influence on the model mean state, all other things being equal. We also find that the existence of a thick category with lower bounds at ∼4 and ∼2 m for the Arctic and Antarctic, respectively, is a prerequisite for allowing the storage of deformed ice and therefore for fostering thermodynamic growth in thinner categories. Our analysis finally suggests that increasing the resolution of the ITD without changing the lower limit of the upper category results in small but not negligible variations of ice volume and extent. Our study proposes for the first time a bi-polar process-based explanation of the origin of mean sea ice state changes when the ITD discretization is modified. The sensitivity experiments conducted in this study, based on one model, emphasize that the choice of category positions, especially of thickest categories, has a primary influence on the simulated mean sea ice states while the number of categories and resolution have only a secondary influence. It is also found that the current default discretization of the NEMO3.6-LIM3 model is sufficient for large-scale present-day climate applications. In all cases, the role of the ITD discretization on the simulated mean sea ice state has to be appreciated relative to other influences (parameter uncertainty, forcing uncertainty, internal climate variability).

A Simple Parameterization of Ice Leads In a General Circulation Model, and the Sensitivity of Climateto Change in Antarctic Ice Concentration

1990 ◽  
Vol 14 ◽  
pp. 266-269 ◽  
Author(s):  
Ian Simmonds ◽  
W.F. Budd
Keyword(s):  
Sea Ice ◽  
General Circulation Model ◽  
General Circulation ◽  
Sensible Heat Flux ◽  
Weighted Average ◽  
Circulation Model ◽  
Open Water ◽  
Weddell Sea ◽  
Antarctic Sea Ice ◽  
Ice Leads

We present a simple parameterization of the effect of open leads in a general circulation model of the atmosphere. We consider only the case where the sea ice distribution is prescribed (i.e., not interactive) and the fraction of open water in the ice is also prescribed and set at the same value at all points in the Southern Hemisphere and a different value in the Northern Hemisphere. We approximate the distribution of sea ice over a model “grid box” as a part of the box being covered by solid ice of uniform thickness and the complement of the box consisting of open water at a fixed -1.8 C. Because of the nonlinearity in the flux computations, separate calculations are performed over the solid sea ice and over the open leads. The net fluxes conveyed to the atmosphere over the grid box are determined by performing the appropriate area-weighted average over the two surface types. We report on an experiment designed to assess the sensitivity of the modelled climate to the imposition of a 50% concentration in the winter Antarctic sea ice. Significant warming of up to 6°C takes place in the vicinity of and above the Antarctic sea ice and is associated with significant changes in the zonal wind structure. Pressure reductions are simulated over the sea ice, being particularly marked in the Weddell Sea region, and an anomalous east-west aligned ridge is simulated at about 60°S. Very large changes in the sensible heat flux (in excess of 200 Wm−2) are simulated near the coast of Antarctica.

scholarly journals The Arctic and Antarctic Sea-Ice Area Index Records versus Measured and Modeled Temperature Data

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Nicola Scafetta ◽  
Adriano Mazzarella
Keyword(s):  
Sea Ice ◽  
General Circulation ◽  
General Circulation Models ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Climate Indices ◽  
Area Index ◽  
Antarctic Sea Ice ◽  
Arctic Sea ◽  
The Antarctic

Here we study the Arctic and Antarctic sea-ice area records provided by the National Snow and Ice Data Center (NSIDC). These records reveal an opposite climatic behavior: since 1978 the Arctic sea-ice area index decreased, that is, the region has warmed, while the Antarctic sea-ice area index increased, that is, the region has cooled. During the last 7 years the Arctic sea-ice area has stabilized while the Antarctic sea-ice area has increased at a rate significantly higher than during the previous decades; that is, the sea-ice area of both regions has experienced a positive acceleration. This result is quite robust because it is confirmed by alternative temperature climate indices of the same regions. We also found that a significant 4-5-year natural oscillation characterizes the climate of these sea-ice polar areas. On the contrary, we found that the CMIP5 general circulation models have predicted significant warming in both polar sea regions and failed to reproduce the strong 4-5-year oscillation. Because the CMIP5 GCM simulations are inconsistent with the observations, we suggest that important natural mechanisms of climate change are missing in the models.

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 Physical characteristics of the Antarctic sea-ice zone derived from modelling and observations

1997 ◽  
Vol 25 ◽  
pp. 1-7 ◽  
Author(s):  
W. F. Budd ◽  
Xingren Wu ◽  
P. A. Reid
Keyword(s):  
Numerical Modelling ◽  
Sea Ice ◽  
Mixed Layer ◽  
Annual Cycle ◽  
Surface Mixed Layer ◽  
Present Climate ◽  
Antarctic Sea Ice ◽  
Mixed Layer Ocean ◽  
The Antarctic ◽  
Ice Model

Antarctic sea ice plays a key role in the present climate system, providing a regulating balance between the atmosphere and ocean heat fluxes, as well as influencing the salt fluxes and deep water formation over the continental shelves. The severe winter environmental conditions of the Antarctic sea-ice zone make it difficult to observe many of the physical characteristics in a comprehensive way. The inter-relations between the variables mean that much can be learnt from the observations of some features along with detailed numerical modelling of the whole system and the interactions between the variables. This study therefore aims to use numerical modelling of the atmosphere, sea ice and surface mixed-layer ocean in the sea-ice zone, together with observations to simulate a comprehensive range of parameters and their variability through the annual cycle to provide a basis for further observations and model validation for the present climate.The model includes a coupled atmospheric general circulation model with an interactive dynamic and thermodynamic sea-ice model and surface mixed-layer ocean. The deep ocean and ocean surface conditions outside the sea-ice zone are constrained to the present mean climate conditions to ensure no climatic drift. The sca-ice model is similar to previous published versions, bill has refined schemes for partitioning of the freezing of frazil ice within the leads and under the ice floes, and for rafting. These perform well in both polar regions with the same physics. The model simulates the annual cycle of atmospheric and sea-ice features well in comparison with data from the global atmospheric analyses, the satellite sensing of sea ice, and the limited in situ surface observations.The output from the model also includes: all components of the heart fluxes, atmospheric profiles and surface temperatures for air, ice and ice-ocean mixtures, open-water fractions, surface snow and snow-ice depths, and the sea-ice convergence-divergence and drift. The comparison of these features with additional observations provides a means for further validating the model and representing the present climate more closely.

scholarly journals Modelling the seasonal variability of the Antarctic Slope Current

Ocean Science ◽  
2011 ◽  
Vol 7 (4) ◽  
pp. 455-470 ◽  
Author(s):  
P. Mathiot ◽  
H. Goosse ◽  
T. Fichefet ◽  
B. Barnier ◽  
H. Gallée
Keyword(s):  
Wind Speed ◽  
Mass Transport ◽  
Sea Ice ◽  
Seasonal Cycle ◽  
Water Mass ◽  
Atmospheric Forcing ◽  
Sensitivity Experiments ◽  
The Mean ◽  
Antarctic Slope Current ◽  
The Antarctic

Abstract. One of the main features of the oceanic circulation along Antarctica is the Antarctic Slope Current (ASC). This circumpolar current flows westwards and contributes to communication between the three major oceanic basins around Antarctica. The ASC is not very well known due to remote location and the presence of sea ice during several months, allowing in situ studies only during summertime. Moreover, only few modelling studies of this current have been carried out. Here, we investigate the sensitivity of this simulated current to four different resolutions in a coupled ocean-sea ice model and to two different atmospheric forcing sets. Two series of simulations are conducted. For the first series, global model configurations are run at coarse (2°) to eddy-permitting (0.25°) resolutions with the same atmospheric forcing. For the second series, simulations with two different atmospheric forcings are performed using a regional circumpolar configuration (south of 30° S) at 0.5° resolution. The first atmospheric forcing is based on a global atmospheric reanalysis and satellite data, while the second is based on a downscaling of the global atmospheric reanalysis by a regional atmospheric model calibrated to Antarctic meteorological conditions. Sensitivity experiments to resolution indicate that a minimum model resolution of 0.5° is needed to capture the dynamics of the ASC in terms of water mass transport and recirculation. Sensitivity experiments to atmospheric forcing fields shows that the wind speed along the Antarctic coast strongly controls the water mass transport and the seasonal cycle of the ASC. An increase in annual mean of easterlies by about 30 % leads to an increase in the mean ASC transport by about 40 %. Similar effects are obtained on the seasonal cycle: using a wind forcing field with a larger seasonal cycle (+30 %) increases by more than 30 % the amplitude of the seasonal cycle of the ASC. To confirm the importance of wind seasonal cycle, a simulation without wind speed seasonal cycle is carried out. This simulation shows a decrease by more than 50 % of the amplitude of the ASC transport seasonal cycle without changing the mean value of ASC transport.

scholarly journals Simulations of Southern Hemisphere warming and Antarctic sea-ice changes using global climate models

1999 ◽  
Vol 29 ◽  
pp. 61-65 ◽  
Author(s):  
Xingren Wu ◽  
W. F. Budd ◽  
T. H. Jacka
Keyword(s):  
Sea Ice ◽  
Greenhouse Gases ◽  
Surface Temperature ◽  
Global Climate ◽  
Coupled Model ◽  
Sea Surface ◽  
Sea Ice Extent ◽  
Antarctic Sea Ice ◽  
The Antarctic ◽  
Ice Model

AbstractA combination of modelling techniques is used in conjunction with the limited available observational data to examine Antarctic sea-ice changes with global warming over the past century. Firstly a coupled global climate model is forced by prescribing the effect of increasing greenhouse gases from last century to the present. Secondly the GISST (U.K. Meteorological Office global sea-ice and sea surface temperature) observational dataset is used to force an atmosphere-sea-ice model to compute changes in the Antarctic sea ice from last century to the present. Thirdly the global sea-surface-temperature (SST) anomalies derived from the coupled model are used to force the atmosphere-sea-ice model over the same period. The change in the Southern Hemisphere annual mean surface temperature simulated by the coupled model with greenhouse-gas forcing is about 0.6°C, which is similar to the observed change. Over the Antarctic (poleward of 60° S) the corresponding simulated change is about 0.7°C, which also appears compatible with observations. The reduction in summer sea-ice extent simulated by the CSIRO (Commonwealth Scientific and Industrial Research Organisation) coupled model is 0.44° lat. which is, in general, less than the observed change. For the two SST forcing cases the changes are, in general, larger than indicated by the observations. It is concluded that future changes of reduced sea-ice extent from increasing greenhouse gases as simulated by the CSIRO coupled model are not expected to be overestimates.

scholarly journals The simulation of Antarctic sea ice in the Hadley Centre Climate Model (HadCM3)

2001 ◽  
Vol 33 ◽  
pp. 585-591 ◽  
Author(s):  
John Turner ◽  
William Connolley ◽  
Doug Cresswell ◽  
Steven Harangozo
Keyword(s):  
Sea Ice ◽  
Satellite Data ◽  
General Circulation ◽  
Climate Model ◽  
Phase Error ◽  
Regional Scale ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Atmospheric Flow ◽  
Antarctic Sea Ice

AbstractAn assessment is presented of the extent and variability of Antarctic sea ice in the non-flux-corrected version of the Hadley Centre’s coupled atmosphere-ocean general circulation model (HadCM3). The results are based on a 100 year segment of a long control run of the model with the sea ice being compared to ice extents and concentrations derived from passive microwave satellite data. Over the year as a whole, the model ice extent (the area with >15% ice concentration) is 91% of that determined from satellite imagery, but, not surprisingly, the regional-scale distribution differs from the observed. Throughout the year there is too much ice near 90° E, which is believed to be present as a result of incorrect ocean currents near Kerguelen. In contrast to the satellite data, there is too little ice to the west of the Antarctic Peninsula as a result of anomalously northerly atmospheric flow, compared to observations. During the winter the sea-ice concentrations in the model are too high, possibly as a result of the simple representation of the sea ice, which does not simulate complex dynamical interactions within the pack. The annual cycle of sea-ice advance/retreat in the model has a phase error, with the winter sea-ice maximum extent being too late by about 1 month.

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