Team Finds Subtropical Waters Flushing Through Greenland Fjord
ScienceDaily (Feb. 17, 2010) — Waters from warmer latitudes -- or subtropical waters -- are reaching Greenland's glaciers, driving melting and likely triggering an acceleration of ice loss, reports a team of researchers led by Fiamma Straneo, a physical oceanographer from the Woods Hole Oceanographic Institution (WHOI).
Recent changes in ocean circulation in the North Atlantic are delivering larger amounts of subtropical waters to the high latitudes. A research team led by Fiamma Straneo, a physical oceanographer at Woods Hole Oceanographic Institution, found that subtropical waters are reaching Greenland's glaciers, driving melting and likely triggering an acceleration of ice loss. Melting ice also means more fresh water in the ocean, which could flood into the North Atlantic and disrupt a global system of currents, known as the Ocean Conveyor. (Credit: Jack Cook, Woods Hole Oceanographic Institution)
"This is the first time we've seen waters this warm in any of the fjords in Greenland," says Straneo. "The subtropical waters are flowing through the fjord very quickly, so they can transport heat and drive melting at the end of the glacier."
Greenland's ice sheet, which is two-miles thick and covers an area about the size of Mexico, has lost mass at an accelerated rate over the last decade. The ice sheet's contribution to sea level rise during that time frame doubled due to increased melting and, to a greater extent, the widespread acceleration of outlet glaciers around Greenland.
While melting due to warming air temperatures is a known event, scientists are just beginning to learn more about the ocean's impact -- in particular, the influence of currents -- on the ice sheet.
"Among the mechanisms that we suspected might be triggering this acceleration are recent changes in ocean circulation in the North Atlantic, which are delivering larger amounts of subtropical waters to the high latitudes," says Straneo. But a lack of observations and measurements from Greenland's glaciers prior to the acceleration made it difficult to confirm.
The research team, which included colleagues from University of Maine, conducted two extensive surveys during July and September of 2008, collecting both ship-based and moored oceanographic data from Sermilik Fjord -- a large glacial fjord in East Greenland.
Sermilik Fjord, which is 100 kilometers (approximately 62 miles) long, connects Helheim Glacier with the Irminger Sea. In 2003 alone, Helheim Glacier retreated several kilometers and almost doubled its flow speed.
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Nature Geoscience
Published online: 14 February 2010 | doi:10.1038/ngeo764
Rapid circulation of warm subtropical waters in a major glacial fjord in East Greenland
Fiammetta Straneo1, Gordon S. Hamilton2, David A. Sutherland1,6, Leigh A. Stearns2,6, Fraser Davidson3, Mike O. Hammill4, Garry B. Stenson3 & Aqqalu Rosing-Asvid5
The recent rapid increase in mass loss from the Greenland ice sheet1, 2 is primarily attributed to an acceleration of outlet glaciers3, 4, 5. One possible cause of this acceleration is increased melting at the ice–ocean interface6, 7, driven by the synchronous warming8, 9, 10 of subtropical waters offshore of Greenland. However, because of the lack of observations from Greenland’s glacial fjords and our limited understanding of their dynamics, this hypothesis is largely untested. Here we present oceanographic data collected in Sermilik Fjord, East Greenland, by ship in summer 2008 and from moorings. Our data reveal the presence of subtropical waters throughout the fjord. These waters are continuously replenished through a wind-driven exchange with the shelf, where they are present all year. The temperature and renewal of these waters indicate that they currently cause enhanced submarine melting at the glacier terminus. Key controls on the melting rate are the volume and properties of the subtropical waters on the shelf, and the patterns of along-shore winds, suggesting that the glaciers’ acceleration has been triggered by a combination of atmospheric and oceanic changes. Our measurements provide evidence for a rapid advective pathway for the transmission of oceanic variability to the ice-sheet margins.topof page
1. Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA
2. Climate Change Institute, University of Maine, Orono, Maine 04469, USA
3. Department of Fisheries and Oceans, St John’s, Newfoundland, A1C 5X1, Canada
4. Department of Fisheries and Oceans, Mont-Joli, Quebec, G5H 3Z4, Canada
5. Department of Birds and Mammals, Greenland Institute of Natural Resources, Postboks 570, 3900 Nuuk, Greenland
6. Present addresses: School of Oceanography, University of Washington, Seattle, Washington 98195, USA (D.A.S.); Department of Geology, University of Kansas, Lawrence, Kansas 66045, USA (L.A.S.)
Correspondence to: Fiammetta Straneo1 e-mail: fstraneo@whoi.edu
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Requer assinatura: Nature Geoscience
