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 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 Processes Controlling Arctic and Antarctic Sea Ice Predictability in the Community Earth System Model

2018 ◽  
Vol 31 (23) ◽  
pp. 9771-9786 ◽  
Author(s):  
Ana C. Ordoñez ◽  
Cecilia M. Bitz ◽  
Edward Blanchard-Wrigglesworth
Keyword(s):  
Sea Ice ◽  
Mixed Layer ◽  
Ocean Dynamics ◽  
System Model ◽  
The Arctic ◽  
Earth System ◽  
Ice Volume ◽  
Antarctic Sea Ice ◽  
The Antarctic ◽  
Area And Volume

Sea ice predictability is a rapidly growing area of research, with most studies focusing on the Arctic. This study offers new insights by comparing predictability between the Arctic and Antarctic sea ice anomalies, focusing on the effects of regional differences in ice thickness and ocean dynamics. Predictability in simulated regional sea ice area and volume is investigated in long control runs of an Earth system model. Sea ice area predictability in the Arctic agrees with results from other studies, with features of decaying initial persistence and reemergence because of ocean mixed layer processes and memory in thick ice. In pan-Arctic averages, sea ice volume and the area covered by thick ice are the best predictors of September area for lead times greater than 2 months. In the Antarctic, area is generally the best predictor of future area for all times of year. Predictability of area in summer differs between the hemispheres because of unique aspects of the coupling between area and volume. Generally, ice volume only adds to the predictability of summer sea ice area in the Arctic. Predictability patterns vary greatly among different regions of the Arctic but share similar seasonality among regions of the Antarctic. Interactive ocean dynamics influence anomaly reemergence differently in the Antarctic than the Arctic, both for the total and regional area. In the Antarctic, ocean dynamics generally decrease the persistence of area anomalies, reducing predictability. In the Arctic, the presence of ocean dynamics improves ice area predictability, mainly through mixed layer depth variability.

scholarly journals Ikaite crystals in melting sea ice – implications for <i>p</i>CO<sub>2</sub> and pH levels in Arctic surface waters

2012 ◽  
Vol 6 (4) ◽  
pp. 901-908 ◽  
Author(s):  
S. Rysgaard ◽  
R. N. Glud ◽  
K. Lennert ◽  
M. Cooper ◽  
N. Halden ◽  
...  
Keyword(s):  
Sea Ice ◽  
Mixed Layer ◽  
Surface Waters ◽  
Elevated Temperatures ◽  
Co2 Exchange ◽  
The Arctic ◽  
Co2 Uptake ◽  
Surface Mixed Layer ◽  
Chemical Transformations ◽  
Antarctic Sea Ice

Abstract. A major issue of Arctic marine science is to understand whether the Arctic Ocean is, or will be, a source or sink for air–sea CO2 exchange. This has been complicated by the recent discoveries of ikaite (a polymorph of CaCO3·6H2O) in Arctic and Antarctic sea ice, which indicate that multiple chemical transformations occur in sea ice with a possible effect on CO2 and pH conditions in surface waters. Here, we report on biogeochemical conditions, microscopic examinations and x-ray diffraction analysis of single crystals from a melting 1.7 km2 (0.5–1 m thick) drifting ice floe in the Fram Strait during summer. Our findings show that ikaite crystals are present throughout the sea ice but with larger crystals appearing in the upper ice layers. Ikaite crystals placed at elevated temperatures disintegrated into smaller crystallites and dissolved. During our field campaign in late June, melt reduced the ice floe thickness by 0.2 m per week and resulted in an estimated 3.8 ppm decrease of pCO2 in the ocean surface mixed layer. This corresponds to an air–sea CO2 uptake of 10.6 mmol m−2 sea ice d−1 or to 3.3 ton km−2 ice floe week−1. This is markedly higher than the estimated primary production within the ice floe of 0.3–1.3 mmol m−2 sea ice d−1. Finally, the presence of ikaite in sea ice and the dissolution of the mineral during melting of the sea ice and mixing of the melt water into the surface oceanic mixed layer accounted for half of the estimated pCO2 uptake.

The Seasonality of submesoscale variability in the Antarctic Seasonal Ice Zone

2020 ◽  
Author(s):  
Isabelle Giddy ◽  
Sarah Nicholson ◽  
Marcel Du Plessis ◽  
Andy Thompson ◽  
Sebastiaan Swart
Keyword(s):  
Sea Ice ◽  
Mixed Layer ◽  
Climate Models ◽  
Critical Role ◽  
Heat Fluxes ◽  
Surface Boundary ◽  
Surface Boundary Layer ◽  
Antarctic Sea Ice ◽  
The Antarctic ◽  
Seasonal Ice Zone

&lt;p&gt;The ocean surface boundary layer in the Southern Ocean plays a critical role in heat and carbon exchange with the atmosphere. Submesoscale flows have been found to be important in setting mixed layer variability in the Antarctic Circumpolar Current (ACC). However, sparsity in observations, particularly south of the ACC in the Antarctic Seasonal Ice Zone (SIZ) where the horizontal density structure of the mixed layer is influenced by sea ice melt/formation and mesoscale stirring, brings into question the ability of climate models to correctly resolve mixed layer variability. We present novel fine-scale observations of the activity of submesoscale variability in the ice-free Antarctic SIZ using three deployments of underwater gliders over an annual cycle. Salinity-dominated density fronts of O(1)km associated with strong horizontal buoyancy gradients are observed during all deployments. There is evidence that stratifying ageostrophic eddies, energised by salinity driven submesoscale fronts are active across seasons, with intermittent equivalent heat fluxes of the same order to, or greater than local atmospheric forcing. This study highlights the need to consider future changes of Antarctic sea-ice in respect to feedback mechanisms associated with salinity (sea-ice) driven submesoscale flows. &lt;/p&gt;

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 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 Sensitivity of the Antarctic sea-ice distribution to oceanic heat flux in a coupled atmosphere-sea-ice model

2001 ◽  
Vol 33 ◽  
pp. 577-584 ◽  
Author(s):  
Xingren Wu ◽  
W. F. Budd ◽  
A. P. Worby ◽  
Ian Allison
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Antarctic Sea Ice ◽  
Oceanic Heat Flux ◽  
Ice Concentration ◽  
Microwave Radiometers ◽  
The Antarctic ◽  
Ice Model

AbstractA coupled atmosphere-sea-ice model is used to study the sensitivity of the Antarctic sea-ice distribution to oceanic heat flux (OHF). Remote sensing of sea ice from microwave radiometers provides data on ice extent and ice concentration. The ice-thickness data used are from ship-based observations. Our simulations suggest that OHF values of 0−5 W m−2 will cause sea ice to be too thick in the model. A value of 20−25 Wm−2 throughout the year causes sea ice to be too thin in the model. The model results indicate that a seasonally varying OHF is required to match the modelled thickness with observations. Values of 5−30 Wm with an annual mean of 10−15 Wm−2, give a reasonable distribution of sea-ice thickness. This agrees with the limited observations of OHF available for the Antarctic. The model results also indicate that the OHF should be varied spatially. When a seasonally and spatially variable OHF is applied to the coupled atmosphere-sea-ice model a still better simulation of the sea-ice distribution is obtained. Our results also suggest that the role of ice advection is very important in the determination of the sea-ice distribution, and it can be quantified by the model.

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

1998 ◽  
Vol 27 ◽  
pp. 413-419 ◽  
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.

scholarly journals Salinity effects on cultured Neogloboquadrina pachyderma (sinistral) from high latitudes: new paleoenvironmental insights

2021 ◽  
Vol 41 (1) ◽  
Author(s):  
Jacqueline Bertlich ◽  
Nikolaus Gussone ◽  
Jasper Berndt ◽  
Heinrich F. Arlinghaus ◽  
Gerhard S. Dieckmann
Keyword(s):  
Sea Ice ◽  
Cold Water ◽  
Weddell Sea ◽  
Wall Thickening ◽  
High Latitudes ◽  
Neogloboquadrina Pachyderma ◽  
Antarctic Sea Ice ◽  
The Antarctic ◽  
Water Species ◽  
Cold Water Species

AbstractThis study presents culture experiments of the cold water species Neogloboquadrina pachyderma (sinistral) and provides new insights into the incorporation of elements in foraminiferal calcite of common and newly established proxies for paleoenvironmental applications (shell Mg/Ca, Sr/Ca and Na/Ca). Specimens were collected from sea ice during the austral winter in the Antarctic Weddell Sea and subsequently cultured at different salinities and a constant temperature. Incorporation of the fluorescent dye calcein showed new chamber formation in the culture at salinities of 30, 31, and 69. Cultured foraminifers at salinities of 46 to 83 only revealed chamber wall thickening, indicated by the fluorescence of the whole shell. Signs of reproduction and the associated gametogenic calcite were not observed in any of the culture experiments. Trace element analyses were performed using an electron microprobe, which revealed increased shell Mg/Ca, Sr/Ca, and Na/Ca values at higher salinities, with Mg/Ca showing the lowest sensitivity to salinity changes. This study enhances the knowledge about unusually high element concentrations in foraminifera shells from high latitudes. Neogloboquadrina pachyderma appears to be able to calcify in the Antarctic sea ice within brine channels, which have low temperatures and exceptionally high salinities due to ongoing sea ice formation.

scholarly journals Dark metabolism: a molecular insight into how the Antarctic sea‐ice diatom Fragilariopsis cylindrus survives long‐term darkness

2019 ◽  
Vol 223 (2) ◽  
pp. 675-691 ◽  
Author(s):  
Fraser Kennedy ◽  
Andrew Martin ◽  
John P. Bowman ◽  
Richard Wilson ◽  
Andrew McMinn
Keyword(s):  
Sea Ice ◽  
Antarctic Sea Ice ◽  
Fragilariopsis Cylindrus ◽  
Dark Metabolism ◽  
The Antarctic ◽  
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