The new study insights into the forces above and below the ocean surface that affect how sea ice moves and disperses in the Arctic Ocean, which is warming twice as fast as the global average. The results can help clarify how climate change is altering the Arctic and inform future climate predictions.
The in-depth analysis reveals how local tidal currents strongly influence the movement of the ice along its path, providing unprecedented insight into how the composition of the seafloor causes some of the most abrupt changes.
Daniel Watkins, a postdoctoral researcher at Brown says “Ice clearly feels the influence of the ocean floor, landscape on the ocean floor, like canyons and continental shelves, affects tides and other ocean currents. And as it drifts, sea ice passes through many different undersea features. We see drastic changes in the dynamics of sea ice once it reaches those undersea features”.
Using data from the largest drifting field of sea ice buoys to date, along with 20 years of satellite imagery, researchers examined the movement of sea ice as it drifted from the Arctic Ocean through a deep-sea passage called the Fram Strait and eventually into the Greenland Sea.
The analysis revealed the impact of the seafloor on some of the most drastic changes affecting sea ice, such as dramatic increases in speed or movements that force the ice to clump together or even break up.
“What we see in this data set is a transition from the central Arctic, where the ice mostly moves as a whole and follows wind patterns, to areas where we see much stronger impacts from ocean currents,” Watkins said.
The Arctic is the fastest-warming part of the globe, and sea ice in the region has long been known to play an important role in the planet’s climate. For example, ice acts as a reflective surface that deflects how much sunlight is absorbed by the Earth. As it disappears, more sunlight is absorbed, leading to a warmer planet. Many scientists also expect that as the Arctic ice disappears.
Through the study, the scientists wanted to delve deeper into the changes taking place in this critically important part of the Earth. Much of the data for the study was collected during the largest polar expedition in history the Multidisciplinary Drift Observatory for the Study of Arctic Climate.
Comprehensive research reveals a sudden increase in ice velocity
During the expedition, teams of researchers took turns spending a year drifting with sea ice aboard a massive German icebreaker in the Arctic Ocean. Watkins was there for two weeks in October 2019 to help install a network of autonomous sensors around base camp.
A total of 214 buoys were deployed during the year-long expedition, including 51 during Watkins’ time on the expedition. The study is based on GPS data transmitted from a set of 108 buoys that traveled from the central Arctic across the Fram Strait and into the Greenland Sea.
The main focus has been on what are known as the fringing ice zones in the Greenland Sea and the Fram Strait, which is the transition zone between the ice-free open ocean and the ice sheet of the central Arctic.
The speed of ice suddenly increased even though the wind did not change
For example, looking at data from an area northeast of Svalbard in Norway, the researchers noticed that the speed of the ice suddenly increased even though the wind did not change. This meant the ice was being pushed by ocean currents, so the team delved deeper to find out where and how this was happening. They found that sea ice is accelerating where the Transpolar Drift Current, one of the Arctic Ocean’s main currents, ends, and the fast-moving East Greenland Current, analysis shows how sea ice responds to different ocean currents and that the sea floor plays a role.
“At the beginning of this trip, there was almost no difference in drift speed across the entire set of buoys,” Watkins said.
The researchers plan to work with model developers to help implement data from the study into predictions of how the ice will move and where it will end up & also plan to further develop an ice sheet tracking tool to track the movement of individual pieces of ice.