<P> Ice enters the sheet through precipitation as snow . This snow is then compacted to form glacier ice which moves under gravity towards the coast . Most of it is carried to the coast by fast moving ice streams . The ice then passes into the ocean, often forming vast floating ice shelves . These shelves then melt or calve off to give icebergs that eventually melt . </P> <P> If the transfer of the ice from the land to the sea is balanced by snow falling back on the land then there will be no net contribution to global sea levels . The general trend shows that a warming climate in the southern hemisphere would transport more moisture to Antarctica, causing the interior ice sheets to grow, while calving events along the coast will increase, causing these areas to shrink . A 2006 paper derived from satellite data, measuring changes in the gravity of the ice mass, suggests that the total amount of ice in Antarctica has begun decreasing in the past few years . A 2008 study compared the ice leaving the ice sheet, by measuring the ice velocity and thickness along the coast, to the amount of snow accumulation over the continent . This found that the East Antarctic Ice Sheet was in balance but the West Antarctic Ice Sheet was losing mass . This was largely due to acceleration of ice streams such as Pine Island Glacier . These results agree closely with the gravity changes . An estimate published in November 2012 and based on the GRACE data as well as on an improved glacial isostatic adjustment model discussed systematic uncertainty in the estimates, and by studying 26 separate regions, estimated an average yearly mass loss of 69 ± 18 Gt / y from 2002 to 2010 . The mass loss was geographically uneven, mainly occurring along the Amundsen Sea coast, while the West Antarctic Ice Sheet mass was roughly constant and the East Antarctic Ice Sheet gained in mass . </P> <P> Antarctic sea ice anomalies have roughly followed the pattern of warming, with the greatest declines occurring off the coast of West Antarctica . East Antarctica sea ice has been increasing since 1978, though not at a statistically significant rate . The atmospheric warming has been directly linked to the mass losses in West Antarctica of the first decade of the twenty - first century . This mass loss is more likely to be due to increased melting of the ice shelves because of changes in ocean circulation patterns (which themselves may be linked to atmospheric circulation changes that may also explain the warming trends in West Antarctica). Melting of the ice shelves in turn causes the ice streams to speed up . The melting and disappearance of the floating ice shelves will only have a small effect on sea level, which is due to salinity differences . The most important consequence of their increased melting is the speed up of the ice streams on land which are buttressed by these ice shelves . </P>

Antarctica's cenozoic glaciers first began to form due to effects caused by the