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- Title
Remarkable properties of cold seawater key to the formation of sea ice on Earth.
- Authors
Roquet, Fabien; Ferreira, David; Schlesinger, Daniel; Madec, Gurvan
- Abstract
Freshwater has the remarkable property of being denser at 4oC than at the freezing point.From a thermodynamic point of view, it means that its thermal expansion coefficient (TEC) isnegative below 4oC (contraction of cold freshwater upon warming). Thanks to this property,a lake may freeze and still maintain a stable stratification with relatively warm waters belowthe cold surface waters, which is critical to sustain favorable life conditions throughout theyear. In contrast, saltwater’s TEC remains positive down to its freezing point so ithas generally been assumed that thermodynamic properties play a lesser role incontrolling the stratification near the freezing point in the ocean. Yet, the TEC ofseawater is typically reduced by more than one order of magnitude between warmtropical and cold polar waters which should have some impact on the stratification inpolar seas. Here we will argue that the temperature dependence of the TEC is infact a major factor controlling the formation of sea ice on Earth as it facilitatesgreatly the generation of a stable salinity stratification trapping cold water near thesurface. To illustrate our hypothesis, we carry out experiments with a fully coupledclimate model, prescribing a range of uniform TECs. It is found that sea ice is formedin the model only when the prescribed TEC value is smaller than a critical value(1.25 10−4 K−1) which is typically associated with seawater at 6oC in the ocean.
- Subjects
SEA ice; HALOCLINE; FREEZING points; WATER; SEA control; SEAWATER
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article