Published on 16 July 2021
A natural seasonal structure known as an “ice arch” performs an important function as a temporary gatekeeper for sea ice in the Arctic Ocean. In most years, the structure takes shape in winter and spans either the southern or northern end of the Nares Strait between Greenland and Ellesmere Island. It works like a barrier to help keep sea ice penned up in the Arctic Ocean—at least until the arch crumbles away in late spring or summer.
A 2021 study led by Kent Moore of the University of Toronto Mississauga found that ice arches in the Nares Strait have been breaking up earlier than usual in recent years or have failed to form at all. The earliest known breakup occurred in 2017, when an ice arch on the northern end of the strait collapsed in early May. In 2018, an ice arch at the strait’s southern end didn’t even form until April. In both cases, the arches lasted for about 120 days.
There are still some years when the ice arch sticks around into summer. That was the case this year, as the ice arch lasted for about 200 days and persisted into July 2021. “There is a lot of variability,” Moore said, “and this year seems to have been a return to a longer-lived arch.”
The image pair above shows the ice arch on June 6, 2021 (left), and July 6, 2021 (right), before and after its collapse. Both images were acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite.