Ocean Currents Could Be Speeding the Retreat of Greenland’s Glaciers
14.06.2010 - Water & Oceans, Ice & Snow, Arctic
According to a team of scientists from Woods Hole Oceanographic Institute (WHOI), the ice loss of glaciers in Greenland could have been caused by changes in the water in the fjords. While the warming air over the glaciers has often been blamed for an increasing ice loss, some scientists have started to investigate the possible role played by the ocean.
In July and September 2008, the team studied Sermilik Fjord in Greenland and measured temperature and salinity at various depths, at four distances along the fjord and across the channel leading into its mouth. At every sampling station in the fjord, from 150 to 200 metres depth down to the bottom, they found the water to be a relatively warm 3.5°C.
A year later, the team revisited Sermilik Fjord and examined the waters in two fjords further north. These fjords provided them crucial data on how changes in the ocean could be influencing the glaciers, but with a lack of past data, the team had to find a fjord whose glacier had not accelerated and could be used as a proxy for the “before” conditions at the other fjords. During their journey, the team deployed 11 moorings and three floats to gather data near the glaciers for a year. They also measured temperature and salinity, from the ocean surface to the bottom of the fjord, at various distances into each of the three fjords.
The researchers found unexpectedly strong currents in the fjords, along with strong winds and storms along the coast just outside the fjords. The winds push surface waters into the fjord, creating a short-term exchange in which ocean water flows in on top and deeper fjord water flows out. After the storm, the flow reverses as surface water flows out and deeper warmer water flows in. Once they get into a fjord, the deeper waters tend to stay warm because the fjord’s narrow shape prevents the water masses from mixing. While polar water stays near the surface, subtropical water stays warm deep in the fjord.
The team is now planning follow-up research to learn more about what is happening at the ice-ocean boundary. If they can retrieve the moorings deployed in 2009, they will provide the first year-round data from the fjords and tell whether the deep warm water stays all year, and how circulation within the fjords changes with the seasons.
