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"The detailed record shows an acceleration, starting around 2002, " said Beata Csatho, one of the study authors and a glaciologist at the State University of NY at Buffalo, in an email.
Since 1992, scientists found that ice losses contributed to a sea level rise of 0.76 cm. Forty percent of that loss has occurred in just the last 5 years, again underscoring the increase in losses recently. It is known to be losing ice rapidly because it is being melted from below by warm ocean waters, a process that is rendering its largest glaciers unstable. By a decade later, between 2002 and 2007, that average annual loss went up to 73 billion metric tons-a 24-billion-metric-ton increase. The latter is increasingly being viewed as posing a potential planetary emergency, because of its enormous size and its role as a gateway that could allow the ocean to someday access the entirety of West Antarctica, turning the marine-based ice sheet into a new sea.
Shepherd told Newsweek that there is a combination of factors that have led to the increased rate of ice loss in recent years, all of which are indicators of climate change.
"Unfortunately, we appear to be on a pathway to substantial ice-sheet loss in the decades ahead, with longer-term consequences for enhanced sea-level rise; something that has been predicted in models for some time".
Moving next to the finger of land pointing to South America called the Antarctic Peninsula, scientists have recorded a sharp rise in air temperatures that force ice shelves to collapse as the surface ice melts.
West Antarctica contributed the most ice loss from the continent, shedding almost 160 billion tonnes each year since 2012. We suggest that Antarctic ice volume variations in response to the range of global temperature experienced over this period - up to 2-3 ̊C above preindustrial, which correspond to future scenarios with Carbon dioxide concentrations between 400 and 500 ppm - are instead driven mostly by retreat of marine ice margins, in agreement with the latest models.
In the most comprehensive Antarctic assessment to date, 84 scientists from 44 organizations analyzed two dozen satellite surveys to take three different kinds of measurements: changes in ice sheet heights, speed and movement of glaciers, and gravity measurements to understand how gravitational attraction relates to the mass of ice sheets overall. "That doesn't mean we should be desperate", Velicogna told AP. The new analysis, which uses satellite, radar, and other tools in the ice-observing toolbox, extends the data to 2017.
A separate study - also published in Nature this week - found that global sea levels could be 3 feet higher by 2070 if nothing is done to curb the ice loss in the next few years. This uncertainty persists because global sea level estimates for the Pliocene have large uncertainties and can not be used to rule out substantial terrestrial ice loss, and also because direct geological evidence bearing on past ice retreat on land is lacking.
"Actions can be taken now that will slow the rate of environmental change, increase the resilience of Antarctica, and reduce the risk that we commit to irreversible changes with widespread impact".
They discovered the acceleration in the rate of ice loss when they did the calculations again for this study, this time with an additional five years of data.
"I think we should be anxious".
Those signs help researchers to gauge the pace of ice retreat in Antarctica - estimated in the past to be about 164 feet (50 meters) each year - between glacial cycles, Shepherd said.