NASA Studies Find Previously Unknown Loss of Antarctic Ice

NASA Studies Find Previously Unknown Loss of Antarctic Ice

Subject :Environment

Section: Climate Change

Context:

• New research on Antarctica, including the first map of iceberg calving, doubles the previous estimates of loss from ice shelves and details how the continent is changing.
• One study, published in the journal Nature, maps how iceberg calving – the breaking off of ice from a glacier front – has changed the Antarctic coastline over the last 25 years. The researchers found that the edge of the ice sheet has been shedding icebergs faster than the ice can be replaced. This surprise finding doubles previous estimates of ice loss from Antarctic’s floating ice shelves since 1997, from 6 trillion to 12 trillion metric tons. Ice loss from calving has weakened the ice shelves and allowed Antarctic glaciers to flow more rapidly to the ocean, accelerating the rate of global sea level rise.

Iceberg Calving

• “Antarctica is crumbling at its edges,” says JPL scientist Chad Greene, lead author of the calving study. “And when ice shelves dwindle and weaken, the continent’s massive glaciers tend to speed up and increase the rate of global sea level rise.”
• Ice shelves act like buttresses to glaciers, keeping the ice from simply sliding into the ocean. When ice shelves are stable, they have a natural cycle of calving and replenishment that keeps their size fairly constant over the long term.
• But in recent decades, the warming ocean has been destabilizing Antarctica’s ice shelves by melting them from below, making them thinner and weaker. Satellite altimeters measure the thinning process by recording the changing height of the ice, but until this study, there hasn’t been a comprehensive assessment of how climate change might be affecting calving around the continent.

Data used from Satellite Missions

• ICESat1(2003),ICESat2– (short for Ice, Cloud and land Elevation Satellite), launched Sept. 15, 2018, part of NASA’s Earth Observing System, is a satellite mission for measuring ice sheet elevation and sea ice thickness, as well as land topography, vegetation characteristics, and clouds
• Cryosat-2 – European Space Agency Earth Explorer Mission that launched on April 8th 2010.
• Envisat– Envisat is a large inactive Earth-observing satellite which is still in orbit and now considered space debris. Operated by the European Space Agency, it was the world’s largest civilian Earth observation satellite
• ERS – European Remote Sensing satellite (ERS) was the European Space Agency’s first Earth-observing satellite programme using a polar orbit. The ERS programme was composed of two missions, ERS-1 and ERS-2, which were launched into the same orbit in 1991 and 1995 respectively. The two spacecraft were designed as identical twins with one important difference – ERS-2 included an extra instrument (GOME) designed to monitor ozone levels in the atmosphere.

Changes in elevation of the Antarctic ice sheet from 1985 to 2021 are shown. Ice height diminishes (red) as the ice sheet melts by contact with ocean water; it rises (blue) where accumulation exceeds melting. Ice shelves are shown in gray. The missions that supplied data are listed at bottom. Credits: NASA/JPL-Caltech