The linked study offers new insights into Antarctic sea ice cover and the influence of seafloor constraints on Southern Ocean currents:
S.V. Nghiem, I.G. Rigor, P. Clemente-Colón, G. Neumann & P.P. Li (August 2016, Available online 11 May 2016), " Geophysical constraints on the Antarctic sea ice cover", Remote Sensing of Environment, Volume 181, Pages 281–292, doi:10.1016/j.rse.2016.04.005
http://www.sciencedirect.com/science/article/pii/S0034425716301481Abstract: "The contrast between the slight increase of Antarctic sea ice and the drastic reduction of Arctic sea ice since the 1970s has been a conundrum to be resolved. Sea ice trajectory tracking with satellite scatterometer data in 2008 shows that ice around Antarctica is pushed offshore by katabatic winds influenced by the continental topography. The ice trajectories reveal that sea ice, grown earlier in the ice season, drifts northward away from the Antarctic continent forming a circumpolar frontal ice zone (FIZ) behind the ice edge. The FIZ thereby consists of sea ice that becomes rougher due to a longer exposure to wind and wave actions, and thicker over time by more ice growth and greater snow accumulation.
In the Antarctic circumpolar sea ice zone adjacent to the sea ice edge, satellite data in 1999–2009 exhibit a band of strong radar backscatter, which is consistent with the signature of older, thicker, and rougher sea ice with more snow in the FIZ. This sea ice band, as wide as 1000 km, serves as a ‘Great Shield,’ encapsulating and protecting younger and thinner ice in the internal ice pack. In the young and thin ice region behind the FIZ, ice can grow rapidly as winds continue opening interior areas thereby creating effective “ice factories.” In addition, ridging can enhance ice thickness by convergence toward the circumpolar FIZ that is recirculated by westerly winds and currents. During the ice growth season, the FIZ advances until reaching lower-latitude warm waters at a boundary determined by the southern Antarctic Circumpolar Current front that is constrained by seafloor features. These persistent topographical and bathymetric geological factors help sustain the Antarctic sea ice cover. As such, the behavior of Antarctic sea ice is not a paradox as some have suggested, but instead is consistent with the geophysical characteristics in the southern polar region that starkly contrast to those in the Arctic."
See also:
http://phys.org/news/2016-05-sea-ice-differences-earth-poles.htmlExtract: "Why has the sea ice cover surrounding Antarctica been increasing slightly, in sharp contrast to the drastic loss of sea ice occurring in the Arctic Ocean? A new NASA-led study finds the geology of Antarctica and the Southern Ocean are responsible.
…
To address the question of how the Southern Ocean maintains this great sea ice shield, the team combined sea surface temperature data from multiple satellites with a recently available bathymetric chart of the depth of the world's oceans. Sea surface temperature data reveal that at the peak of ice growth season, the boundary of the ice shield remains behind a 30-degree Fahrenheit (-1 degree Celsius) temperature line surrounding Antarctica. This temperature line corresponds with the southern Antarctic Circumpolar Current front, a boundary that separates the circulation of cold and warm waters around Antarctica. The team theorized that the location of this front follows the underwater bathymetry.
When they plotted the bathymetric data against the ocean temperatures, the pieces fit together like a jigsaw puzzle. Pronounced seafloor features strongly guide the ocean current and correspond closely with observed regional Antarctic sea ice patterns. For example, the current stays near Bouvet Island, located 1,000 miles (1,600 kilometers) from the nearest land, where three tectonic plates join to form seafloor ridges. Off the coast of East Antarctica, the -1 degree Celsius sea surface temperature lines closely bundle together as they cross the Kerguelen Plateau (a submerged microcontinent that broke out of the ancient Gondwana supercontinent), through a deep channel called the Fawn Trough. But those lines spread apart over adjacent deep ocean basins, where seafloor features are not pronounced. Off the West Antarctica coast, the deep, smooth seafloor loses its grip over the current, allowing sea ice extent to decrease and resulting in large year-to-year variations."
