This photo shows the vast ice landscape of the huge Thwaites Glacier in West Antarctica. The air currents prevailing there cause heavy snowfalls in winter, but bring thawing weather in summer.
Thousands of kilometers long but narrow air currents can form in certain zones of the atmosphere. Over the Pacific, such atmospheric rivers often originate southwest of Hawaii, and then flow across the island chain towards the northern US west coast and Canada. There they are one of the main causes of extensive, heavy rainfall. But such currents also exist in other regions of the atmosphere.
A research team led by Susheel Adusumilli from the University of California San Diego has now investigated whether they have already caused increased rainfall in West Antarctica, such as on the Thwaites Glacier in our photo. To do this, the scientists used the data from NASA’s ICESat-2 satellite, which has been using laser pulses to measure the height of the ice and snow in Antarctica since 2018, and a computer model that provides information on the atmosphere and humidity based on weather data.
It showed that the height of the ice sheet in West Antarctica increased again and again significantly between April 2019 and June 2020. The Thwaites Glacier also got more snow during this time. Around 40 percent of the increase in altitude during the southern winter of 2019 can be attributed to short but heavy snowfalls. According to Adusumilli and her team, more than 60 percent of this precipitation was caused by atmospheric rivers. These transport humid air and low pressure areas from the subtropical, mid-latitudes of the southern hemisphere to the Antarctic and thus trigger rather mild temperatures and snowfall in winter.
In the southern summer, on the other hand, the atmospheric rivers have the opposite effect: Because they then bring warm air into the Antarctic latitudes, they contribute to the warming and thawing of the ice. As the researchers found, 90 percent of summer atmospheric fluxes and ten percent of winter fluxes coincided with phases of ice melting in the West Antarctic ice sheet.
“We know that the frequency of atmospheric fluxes will increase, so it is important that scientists can determine how much they are contributing to snowfall or surface melt,” explains Adusumilli. “This helps us to better understand how the ice mass of the Antarctic is changing overall and how this affects the sea level.”