A recent large-scale survey of Antarctica’s ice sheets has revealed that the rate of ice melt from the (mostly) frozen southern continent has tripled over the last decade, releasing volumes of water into the ocean on par with the freshwater flow from Greenland. Increasing temperatures from the air above and the ocean below has accelerated the melting of the ice shelves in West Antarctica, and overall ice sheet growth in East Antarctica has slowed. Additionally, the loss of ice mass in the south means that sea level rise will be more pronounced in the north, spelling trouble for populations living in coastal areas, including those of the United States.
The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) is an initiative involving 84 scientists, 44 international organizations and 24 satellite surveys. The IMBIE’s assessment found that Antarctica shed 219 billion tonnes (241.41 billion tons) per year between 2012 and 2017, nearly triple the pre-2012 annual rate of 76 billion tonnes (83.8 billion tons). This also brought Antarctica’s contribution to annual sea level rise to 0.6 millimeters (0.024 inches), three times the pre-2012 amount of 0.2 millimeters (0.008 inches). Antarctica’s ice loss has contributed to 7.6 millimeters (0.3 inches) of sea level rise since 1992, but a full 3.0 millimeters (0.12 inches) was added in the last five years alone — that’s two-fifths of the increase happening in just the last one-fifth of that time period.
The brunt of the melt is being experienced in West Antarctica, particularly from the massive Pine Island and Thwaites Glaciers, each with ice sheets that flow out over the ocean, a situation that exposes their ice shelves to warmer ocean water from underneath in addition to the air above. Ice melt in the West itself has increased to 159 billion tonnes (175.3 billion tons) per year since 2012, up from a pre-2012 annual rate of 53 billion tonnes (58.4 billion tons). Further east, ice shelf collapse on the Antarctic Peninsula has contributed to an increase in ice loss of 25 billion tonnes (27.6 billon tons) per year since the early 2000s.
"According to our analysis, there has been a steep increase in ice losses from Antarctica during the past decade, and the continent is causing sea levels to rise faster today than at any time in the past 25 years," warns University of Leeds Professor Andrew Shepherd, Director for the Centre for Polar Observation and Modelling. "This has to be a concern for the governments we trust to protect our coastal cities and communities."
The acceleration of ice melt in Antarctica could also be expected to affect northern latitudes more than southern regions, including coastal areas of the United States. According to Rob DeConto, a climate scientist at the University of Massachusetts, the loss of mass in the Antarctic ice sheets will reduce the continent’s subtle southward gravitational pull on the world’s oceans (yes, the Antarctic ice sheet is that massive), slowly allowing the water to effectively slosh northward.
"The Earth’s gravitational field changes because we’re redistributing mass around the planet," according to DeConto. DeConto expects that for every unit of sea level rise that Antarctica contributes to, the effect will add 25 percent more to sea level rise to northern latitudes, as water from southern regions are allowed to flow north.
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