Rapid evolution of a proglacial coastal lake 20 th and 21 th century changes in Jökulsárlón at Breiðamerkursandur, Vatnajökull, Iceland 1 Sverrir Guðmundsson 1 Helgi Björnsson 1 Finnur Pálsson 2 Etienne Berthier 1 Earth Science Institute, University of Iceland 2 LEGOS, Toulouse, France
Overview Site description: Breiðamerkurjökull glacier/ Jökulsárlón lake - Surface and bedrock topography Formation and evolution of Jökulsárlón - 20 th century glacier retreat - Ice fluxes, calving rates - Energy balance of the lake Modelling iceflow and lake evolution - Observations - Iceflow, calving and mass balance model - Predicted future changes - Comparison to coupled iceflow- and mass balance model of southern Vatnajökull (Aðalgeirsdóttir and others)
Landsat 1 MSS image, USGS Vatnajökull icecap Jökulsárlón lake Breiðamerkurjökull outlet glacier
Breiðamerkurjökull Surface topography Glacier area 994 km 2 Jökulsárlón Lake area 17.4 km 2
Breiðamerkurjökull Sub-ice topography mapped by radio echo sounding 1991 Not measured 25 km long trench below sea level Jökulsárlón
Overview Site description: Breiðamerkurjökull glacier/ Jökulsárlón lake - Surface and bedrock topography Formation and evolution of Jökulsárlón - 20 th century glacier retreat - Ice fluxes, calving rates - Energy balance of the lake Modelling iceflow and lake evolution - Observations - Iceflow, calving and mass balance model - Predicted future changes - Comparison to coupled iceflow- and mass balance model of southern Vatnajökull (Aðalgeirsdóttir and others)
Formation of Jökulsárlón since 1933 Glacier retreat 1903-2004 Ice Bedrock
Ice reduction in Jökulsárlón since 1933 Calving ice flux estimated from : I i : ice flux towards lagoon through a cross section above lagoon (from cross section area and flow velocity) I b : surface mass balance on snout between cross section and lagoon I h : net ice volume change (thinning) between lagoon and cross section I l : net ice volume change between lagoon and cross section due to change in margin position
Energy supplied to ice melting in Jökulsárlón since 1933
From Landmælingar Íslands
- Breiðamerkurjökull and Breiðamerkurlón. - SPOT5, August 2004 - Pixel resolution 2.5 x 2.5 m
- Breiðamerkurjökull and Breiðamerkurlón. - SPOT5, August 2004 - Pixel resolution 2.5 x 2.5 m
Esjufjöll Breiðamerkurjökull Photo: Helgi Björnsson 1990
Breiðamerkurjökull Photo: Helgi Björnsson 1990
Overview Site description: Breiðamerkurjökull glacier/ Jökulsárlón lake - Surface and bedrock topography Formation and evolution of Jökulsárlón - 20 th century glacier retreat - Ice fluxes, calving rates - Energy balance of the lake Modelling iceflow and lake evolution - Observations - Iceflow, calving and mass balance model - Predicted future changes - Comparison to coupled iceflow- and mass balance model of southern Vatnajökull (Aðalgeirsdóttir and others)
Observed mass balance and thinning rate
Sonic echo sounder at 200 m a.s.l. May 5, 2002 ~ 40 cm
Sonic echo sounder at 200 m a.s.l. July 23, 2002 Steini
Sonic echo sounder at 200 m a.s.l.
Observed glacier surface velocity Observations: -DGPS -SPOT5 correlation DGPS
Observed glacier surface velocity Observations: -DGPS -SPOT5 correlation SPOT5 correlation: Input: 2 optical images (2.5 X 2.5 m) Output: 2D horizontal displacement SPOT5, August 11, 2004 SPOT5, Sept. 26, 2004 Correlation and mass balance correction V C V L Horizontal displacement V H
Observed glacier surface velocity Observations: -DGPS -SPOT5 correlation Horizontal velocity inferred from two SPOT5: August 11 and September 26, 2004 At the calving front Esjufjöll Jökulsárlón SPOT5 velocity: LEGOS and CNES, Toulouse, France
Coupled iceflow-calving models Mass balance model tuned to observations since 1996 Calving model Iceflow model Ice Bedrock
Predicted response to present-day climate Average climate condition since 1996 Ice Bedrock Ice Bedrock
Southern Vatnajökull: coupled iceflow-mass balance models Predicted response to the average climate conditions of 1981-2000 zero annual mass balance Guðfinna Aðalgeirsdóttir and others, in press (JGR)
Reasponse to climate scenario Based on CWE climate change scenario near Iceland, 1990-2050. Temperature changes approximated by: sinusoidal annual variation. continious linear warming: maximum of +0,3 C per decade (winter) and a minimum of 0,15 C per decade (summer). Precipitation changes: monthly fluctuations appear without a clear climate change signal. simplified to 5% per 1 C warming, independent of the season.
Southern Vatnajökull: coupled iceflow-mass balance models Predicted response to the CWE climate scenario By Guðfinna Aðalgeirsdóttir and others, in press (JGR)
Conclusions Site description - Jökulsárlón is the southernmost part of a 25 km long trench Formation and evolution of Jökulsárlón - 20th century glacier retreat: 5.6 km - Lake appeared in 1933, and was at the year 2004: 17.4 km 2 - Present calving flux: 0.25 km 3 a -1 - Velocity at calving front: 500 m a -1 - Thinning rate at calving front: 8 m a -1 (ablation 13 m ice a -1 ) - Present energy supply for melting lake ice: ~3000 MW of which half provided by ocean water Predictions - Near-future lake growth rate: 0.4 km 2 a -1 - Lake ~25 km long after 200 years - Glacial sediment deposit in the lake and not compensating for coastal abrasion - Input to studies of earth response to glacier variations