Antarctica is one of eight ecozones or biogeographical regions on Earth. With an area of 14 million km², to which are added 1.5 million km² of barriers, it is the fourth largest continent in the world. By convention, the geographical boundary is delimited by the so-called Antarctic convergence, the latitude where the subtropical surface waters sink.
The area between 50° and the Antarctic Circle is called sub-Antarctic. On average it is the coldest place on Earth and with the largest reserves of fresh water on the planet. The territory has the highest mean altitude above sea level of all continents.
Antarctica is considered a desert, with annual rainfall of only 200mm along the coast, and much less in inland regions. The continent is crossed by the 3500 km long Transantarctic Range which extends from Cape Adare to Coats Land.
The ice sheet covering Antarctica is divided into the East and West ice sheets by the Transantarctic Range. The maximum thicknesses of the ice cap are found at the Land of Adelia just 400 km from the coast: here there is a deep depression filled by 4776 m of ice.
If we consider the mass of ice that covers the surface, Antarctica is the continent on average the highest above sea level. On the other hand, excluding the profile given by the ice caps and considering exclusively the average level of the rock layer, this continent is on average the lowest.
Antarctic coastal exposure has changed dramatically over the past 30 years
Change and variability in Antarctic coastal exposure, 1979-2020, study published on the Nature communications, makes a profound retrospective on the topic.
The researchers explained: "Increased exposure of Antarctica's coastal environment to open ocean and waves due to loss of a protective sea-ice "buffer" has important ramifications for ice-shelf stability, coastal erosion, important ice-ocean-atmosphere interactions and shallow benthic ecosystems.
Here, we introduce a climate and environmental metric based on the ongoing long-term satellite sea-ice concentration record, namely Coastal Exposure Length.This is a daily measure of change and variability in the length and incidence of Antarctic coastline lacking any protective sea-ice buffer For 1979-2020, ~50% of Antarctica's ~17,850-km coastline had no sea ice offshore each summer, with minimal exposure in winter.
Regional summer/maximum contributions vary from 45% (Amundsen-Bellingshausen seas) to 58% ( Indian Ocean and Ross Sea), with circumpolar annual exposure ranging from 38% (2019) to 63% (1993).The annual maximum length of Antarctic coastal exposure decreased by ~30 km (~0.32%) per year for 1979-20 20, composed of distinct regional and seasonal contributions."