TY - ABST

T1 - Drainage of ice-dammed lakes and glacier retreat - a link

AU - Kjeldsen, Kristian Kjellerup

AU - Kjaer, K. H.

AU - Rysgaard, Søren

AU - Mortensen, J.

PY - 2011/12/1

Y1 - 2011/12/1

N2 - Recent years investigations have suggested that the circulation of warm seawater along the coast of Greenland play an important role for the mass balance of the Greenland Ice Sheet. A key driving force for the circulation is the contribution of meltwater in the inner parts of fjord systems where surface freshwater run-off is found in the top of the water column in the fjord while sub-glacial meltwater is entrained deeper in the water column. The latter is highly important as this colder buoyant freshwater is pushed to the water surface followed by a compensating deeper landward current bringing warm salty water to the glacier front. In early September 2009, the lake Illuliartôq, dammed by the Narssap Sermia glacier in Godthåbsfjorden, drained during a weekend. Large amounts of cold fresh meltwater draining into the fjord at the base of the glacier where it contributed to the water circulation in the fjord. The large quantity of buoyant freshwater changed the osmotic pressure and pushed redfish to the water surface causing them to die from divers disease. Further investigation suggested that three ice-dammed lakes adjacent to the Narssap Sermia glacier had drained within the previous year. Analysis of the water masses in Godthåbsfjorden shows that the sudden drainage of ice-dammed lakes not only affects the marine ecosystem but also has a tremendous effect on the circulation of water masses within the fjord. Preliminary results suggest that the drainage causes a landward flow of warm seawater which is 10-30 times the volume of an ice-dammed lake prior to drainage. The warm water influx in turn causes the glacier to retreat and to gradually become thinner which feeds back to an increase in drainage events of ice-dammed lakes over time. On a larger scale the feedback mechanism between the drainage of lakes, the circulation of water masses and the retreat of tidewater glaciers may suggest a speedup of the melting of the Greenland Ice Sheet.

AB - Recent years investigations have suggested that the circulation of warm seawater along the coast of Greenland play an important role for the mass balance of the Greenland Ice Sheet. A key driving force for the circulation is the contribution of meltwater in the inner parts of fjord systems where surface freshwater run-off is found in the top of the water column in the fjord while sub-glacial meltwater is entrained deeper in the water column. The latter is highly important as this colder buoyant freshwater is pushed to the water surface followed by a compensating deeper landward current bringing warm salty water to the glacier front. In early September 2009, the lake Illuliartôq, dammed by the Narssap Sermia glacier in Godthåbsfjorden, drained during a weekend. Large amounts of cold fresh meltwater draining into the fjord at the base of the glacier where it contributed to the water circulation in the fjord. The large quantity of buoyant freshwater changed the osmotic pressure and pushed redfish to the water surface causing them to die from divers disease. Further investigation suggested that three ice-dammed lakes adjacent to the Narssap Sermia glacier had drained within the previous year. Analysis of the water masses in Godthåbsfjorden shows that the sudden drainage of ice-dammed lakes not only affects the marine ecosystem but also has a tremendous effect on the circulation of water masses within the fjord. Preliminary results suggest that the drainage causes a landward flow of warm seawater which is 10-30 times the volume of an ice-dammed lake prior to drainage. The warm water influx in turn causes the glacier to retreat and to gradually become thinner which feeds back to an increase in drainage events of ice-dammed lakes over time. On a larger scale the feedback mechanism between the drainage of lakes, the circulation of water masses and the retreat of tidewater glaciers may suggest a speedup of the melting of the Greenland Ice Sheet.

KW - [0700] CRYOSPHERE

KW - [0720] CRYOSPHERE / Glaciers

KW - [0746] CRYOSPHERE / Lakes

KW - [0758] CRYOSPHERE / Remote sensing

M3 - Conference abstract for conference

ER -