The front of every ice shelf on the southern Antarctic Peninsula has retreated since 1947 according to the U.S. Geological Survey. Antarctic Peninsula Ice shelf map - large PDF The systematic retreat of all of the ice shelves in the coldest part of the Antarctic peninsula is evidence that warming temperatures are beginning to remove the floating ice that keeps Antarctica's outlet glaciers from rapidly flowing into the sea.
The dramatic retreat of the Wilkins ice shelf.
Rapid warming of the Antarctic peninsula, causing the retreat of ice shelves, is threatening global sea level rise. A pattern of ice shelf retreat has been seen on both sides of the Antarctic Peninsula on ice fronts of all sizes.
Systematic ice front retreat is evident. (PDF)
The retreat of ice shelves, a possible precursor to the deglaciation of West Antarctica predicted by Mercer (1978), has been tied to the significant and consistent warming trend of the peninsula area, documented by King (1994) and others. According to a review by Vaughan and others (2003), the Antarctic Peninsula warming rate of 3.7±1.6°C per century is an order of magnitude larger than the global mean warming rate of 0.6±0.2°C.
(figure inserted by diarist showing Antarctic surface temperatures to illustrate quote)
Many researchers have observed, described, monitored, and analyzed the ongoing changes in the Antarctic Peninsula using field work, a large variety of remotely sensed data, and mathematical modeling, and have discussed the probable mechanics of the retreat. Most research has focused on the dramatic changes of the larger ice shelves and their tributary glaciers, but substantial change has been occurring in many smaller ice fronts of the Antarctic Peninsula. Although the changes occurring on the eastern side of the peninsula are more dramatic and more noticeable, the changes occurring on the western side are equally important and also have the potential of affecting the mass balance of the entire Antarctic Peninsula.
2008 Satellite images of the collapse of the Wilkins ice sheet
The warming of the Southern ocean, which surrounds Antarctica, is is melting the ice sheets from below. Antarctic bottom water temperatures are rising. PMEL, in press, PDF (Antarctic Bottom Water Warming Between the 1990s and the 2000s: Contributions to Global Heat and Sea Level Rise Budgets)
The warming of the deep water is directly causing sea level to rise.
Deep (1000–4000 m) warming of waters mostly of Antarctic origin south of the Sub-Antarctic Front of the Antarctic Circumpolar Current adds 0.065 (±0.063) W m–2. The warming below 4000 m produces a 0.047 (±0.020) mm yr–1 increase in global average sea level and the deep warming south of the Sub-Antarctic Front adds another 0.087 (±0.083) mm yr–1.
Satellite altimetry derived temperature profiles show Antarctica is surrounded by warmer than normal water at 100 meters depth. The warmer than normal water is melting Antarctic ice sheets from below.
The flow of Antarctic ice into the southern ocean that will increase with the retreat of ice shelves is expected to add to the expansion driven rise caused by the warming of the water.