Antarctic sea ice
Antarctic sea ice describes the sea ice state in the Southern Ocean. The IPCC AR5 report concluded that it is very likely that annual mean Antarctic sea ice extent increased 1.2 to 1.8% per decade, which is 0.13 to 0.20 million km2 per decade, during the period 1979 to 2012. Though, some regions show decreasing and in others increasing rates of sea ice extent.
Measurements of sea ice
The sea ice extent in Antarctica peaks during September, which marks the end of Southern Hemisphere winter, and retreats to a minimum in February.
Temperatures in the atmosphere and Southern Ocean have increased during the period 1979–2004. However, sea ice growths faster than sea ice melts, because of a weakly stratified Ocean. Thus, this mechanism is responsible for an increase in the net ice production, contributing to more sea ice.
Model simulations suggest, that in the sum Antarctic sea ice thickness has increased by approximately 30 km3 per year (0.4%), and an equally result of areal expansion 20 × 103 km2 per year (0.2%) and a thickening of 1.5 mm per year (0.2%). The sea ice volume increase presents about half the size of the increased freshwater supply from the Antarctic ice sheets. Further does the model suggests that observed ice-drift toward the coastal regions are responsible for dynamical thickening during autumn and winter.
Satellite measurements by ESA’s CryoSat-2 revealed that the West Antarctic Ice Sheet (WAIS) is losing more than 150 cubic kilometres of ice each year, especially pronounced at grounding lines, the area where the floating ice shelf and the part resting on bedrock are. Hence, affecting the ice shelf stability and flow rates.
Implications for sub-surface temperatures and coastal currents have been identified, mainly related to changes in the southern hemispheric westerly winds, among possible implications is rapid Glacier melting, thus affecting calving rates and subsequently sea ice formation.
- IPCC AR5 WG1 (2013). PDF The Physical Science Basis. p. 7.
- NASA. "Antarctic Sea Ice".
- Zhang, Jinlun (2007). [PDF Abstract "Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions"]. Climate. doi:10.1175/JCLI4136.1.
- Holland, Paul R., Nicolas Bruneau, Clare Enright, Martin Losch, Nathan T. Kurtz, Ron Kwok (January 17, 2014). "Modeled Trends in Antarctic Sea Ice Thickness". Climate 27 (10): 3784–3801. doi:10.1175/JCLI-D-13-00301.1.
- ESA (December 11, 2013). "Antarctica’s ice loss on the rise".
- Paul Spence, Stephen M. Griffies, Matthew H. England, Andrew Mc C. Hogg, Oleg A. Saenko and Nicolas C. Jourdain (2014). "Rapid subsurface warming and circulation changes of Antarctic coastal waters by poleward shifting winds". Geophysical Research Letter. doi:10.1002/2014GL060613.
- Matthew H. England, Shayne McGregor, Paul Spence, Gerald A. Meehl, Axel Timmermann, Wenju Cai, Alex Sen Gupta, Michael J. McPhaden, Ariaan Purich & Agus Santoso (February 9, 2014). "Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus". Nature Climate Change 4: 222–227. doi:10.1038/nclimate2106.