Global sea level rise is understood to be one of the most serious consequences of global warming and according to NOAA (the National Oceanic and Atmospheric Administration), sea level is rising at an increasing rate. Global sea level rise is caused by warming of the ocean and consequent thermal expansion (since water expands as it warms) and increased melting of land-based ice, such as glaciers and ice sheets. Melting ice and warming waters have all been primarily driven by human emissions of greenhouse gases.
Melting Antarctica does pose a serious threat because 60 and 90 % of the world’s fresh water is frozen in its ice sheets. In other words, if all that ice melted, it would be enough to raise the world’s sea levels by roughly 200 feet. Study published in June 2018 in Nature is particularly worrying, since it shows that Antarctica’s melting is speeding up (See Mass balance of the Antarctic Ice Sheet from 1992 to 2017 published by the IMBIE team). “We used different satellite missions and techniques because the various approaches we have at arriving at this number have different strengths and weaknesses,” said Andrew Shepherd, a professor of earth observation at the University of Leeds and the lead author of the study. Researchers found that the rate at which Antarctica is losing ice has tripled since 2007. Current rate of melting would contribute 15 cm to sea-level rise by 2100. Prof Andrew Shepherd explains: “Around Brooklyn you get flooding once a year or so, but if you raise sea level by 15 cm then that’s going to happen 20 times a year.”
Scientists are anxious about the balance of how much snow and ice accumulates in a given year versus the amount that is lost. According to their data, Antarctica shed 3 trillion tons of ice between 1992 and 2017, and 40 % of that increase came from the last five years. The study also sheds light on what’s driving the loss of ice in Antarctica. Satellite observation revealed that we’re losing more mass along the edges of the ice sheet, where the ice sheet is making contact with the ocean. Scientists conclude that the warming oceans are the main driver causing Antarctic ice loss.