Writing in the journal Geophysical Research Letters, a team led by Son Nghiem of NASA's Jet Propulsion Laboratory describe a sudden influx of warm river waters into the sea in 2012 that rapidly warmed the surface layers of the ocean, enhancing the melting of sea ice.
The team used data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA's Terra satellite to examine sea ice in the Beaufort Sea, then compared it to reports of river discharge from the Mackenzie River in western Canada.
They found that on June 14, 2012, a stretch of landfast sea ice (sea ice that is stuck to the coastline) formed a barrier that held the river discharge close to its delta. Sometime over the next three weeks, that barrier had disappeared and the average surface temperature of the area of open water in the area increased by 11.7 degrees Fahrenheit (6.5 degrees Celsius).
"When the Mackenzie River's water is held back behind the sea ice barrier, it accumulates and gets warmer later in the summer," said Nghiem. "So when it breaks through the barrier, it's like a strong surge, unleashing warmer waters into the Arctic Ocean that are very effective at melting sea ice. Without this ice barrier, the warm river waters would trickle out little by little, and there would be more time for the heat to dissipate to the atmosphere and to the cooler, deeper ocean."