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AGAP S |
Subglacial Lakes |
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Subglacial Lakes EXTERNAL LINKS
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This image (created by Zina Deretsky/NSF) is a rendering of the complex network of ice streams and lakes that scientists have found exist under the ice sheet in Antarctica. The movement of water through this under-ice network affects the overlying ice sheet and the dynamics of the many ice streams that carry ice from the center of the continent towards the surrounding ocean. There is still much that is unknown about this process. Understanding the linkages between ice sheets and underlying subglacial environments is a key piece of this research as well as other research being conducted as part of the current IPY. |
Although scientists have not yet sampled in any of the lakes they have collected enough data from radar, gravity and other remote methods to learn that water moves in and out of these lakes, connecting under the ice in a rather elaborate plumbing system. While we don’t fully understand this system , we know this plumbing system has important consequences for the overlying glacier. Subglacial lakes that connect and drain into ice streams that flow under the ice sheet, can significantly increase the movement of the overlying ice. Ice movement in the interior of Antarctica has been measured at about 2 meters a year. Water flowing out of the subglacial lakes can cause a ‘greasing’ underneath the ice sheet that actually floats the ice sheet off the bedding underneath causing it to slide along like a sled on a slick base. This acceleration of movement from the underlying water can escalate glacier movement from 2 meters to 2 kms a year! This means that slow moving ice in the interior of Antarctica could be accelerated so that it moves more quickly towards the exterior edges of the continent where it can be warmed by ocean currents causing ice sheet melting. While scientists don’t yet know if subglacial lakes actually cause the onset of ice stream movement, it is something we hope to learn more about through this IPY project.
Ho do subglacial lakes speed the ice flow? Using satellite measurements, Bell et al. (Nature 445 904–907 (2007).) found four subglacial lakes right at the onset of fast ice flow at the Recovery Glacier ice stream in Dronning Maud Land, Antarctica. They propose that the freezing of lake water to the base of the ice sheet (pink area), together with water spilling over from the lake and scouring the bedrock, could reduce friction and help speed up ice flow towards the sea. How do satellite measurements work? The relative strength of reflection of ground-based radar distinguishes between bedrock and water at the base of an ice sheet, and the characteristic flat area in the ice surface above a subglacial lake can be detected by satellite-based surface observations. Image and caption by permission from Macmillan Publishers Ltd: Nature, Kohler, J., Glaciology: Lubricating lakes, 445, 830-831(22 February 2007) |