docChanges in precipitation associated with the thinning of
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Changes in precipitation associated with the thinning of
Changes in precipitation associated with the thinning of Vatnajökull ice cap Hálfdán Ágústsson, Haraldur Ólafsson, Helgi Björnsson and Finnur Pálsson University of Iceland, Icelandic Meteorological Office, Belgingur, Bergen school of Meteorology and Earth science institute Photo: Snævarr Guðmundsson Glaciers in Iceland have retreated and thinned significantly since the end of the Little Ice Age Photo: Frederick W. W. Howell 1891 Kotárjökull and Rótarfjallsjökull in Kotárgil, view from Howellssteinn Photo: Snævarr Guðmundsson 2011 Glacier surface of three outlets near Höfn Skálafellsjökull Heinabergsjökull Fláajökull LIA max We are here! Reconstructed glacier surface geometry Hannesdóttir et al., 2015 Glacier surface of three outlets near Höfn 1904 Maps of the Danish General Staff Hannesdóttir et al., 2015 Glacier surface of three outlets near Höfn 1946 AMS maps of the American army Hannesdóttir et al., 2015 Glacier surface of three outlets near Höfn 1989 DMA maps of the Defense agency Hannesdóttir et al., 2015 Glacier surface of three outlets near Höfn 2000 DGPS measurements Hannesdóttir et al., 2015 Glacier surface of three outlets near Höfn 2010 LiDAR DEM Tómas Jóhannesson, Hannesdóttir et al., 2015 Simulations future warming +2°C &10% increase P 300 year simulation +3°C & 10% increase P 300 year simulation Hannesdóttir et al., 2015 Mean annual precipitation (MM5) Meterol. Z, Rögnvaldsson et al. 2007 Mean annual precipitation (MM5) Control simulation Flat Iceland 60-90% increase in precipitation due to the mountains and ice cap! Meterol. Z, Rögnvaldsson et al. 2007 Annual precipitation in Iceland 1960-1990 in a linear model Study region Philippe Crochet & Tómas Jóhannesson Kvísker 293 mm/24h Upstream and downstream extremes! Philippe Crochet & Tómas Jóhannesson Annual precipitation in Iceland 1960-1990 in a linear model Extensive harnessing of hydropower Philippe Crochet & Tómas Jóhannesson Land surface types and soil erosion in Iceland Biggest dust source in the arctic DESERT Ó. Arnalds et al. Haraldur Ólafsson Haraldur Ólafsson Current ice cap elevation Unique measurements have been made of the thickness of the ice caps Height change if ice cap disappears Bedrock below Vatnajökull Annual precipitation Control simulation What is the effect of Vatnajökull ice cap on the precipitation distribution and magnitude in the region? Annual precipitation Sensitivity simulation WRF atmospheric model at 2 km ● Two years: 2004-2006 ● Compare precipitation in two simulations: ➔ Ctrl: Current surface ➔ Sensitivy: No ice cap ● Sensitivity - control Annual precipitation decrease without ice cap (Sensitivity-control) / control Relative Annual precipitation decrease Sensitivity / control Relative Annual precipitation SUMMER (Sensitivity-control) / control Relative annual precipitation decrease WINTER SUMMER Sensitivity / control Relative Annual precipitation WINTER Sensitivity / control Relative Annual precipitation Watershed of Fljótsdalsvirkjun hydro power plant Summary: Relative Annual precipitation Precipitation distribution in a warming climate? Change in distribution in a 2°C warmer atmosphere (normal - warm) It is generally estimated that a 1°C warming will on average be accompanied by a 2-4% increase in precipitation at the latitudes of Iceland. mm/18 hrs 25. sept. 2010 Concluding remarks +10% decrease in precipitation on Vatnajökull without the ice cap Largest changes in the SW and NE +20% (+25%) decrease in precipitation on some watersheds on the ice cap Only minor changes in the „precipitation shadow“ to the north The „background“ runoff will change as the glacier retreats in warming climate (and many thanks to Eyjólfur Magnússon for preparing the bedrock data of the ice caps)