Kilder: NSIDC & Univ. Bremen 10/6/2010 Isbreer, klima og havnivå Nordlige sjørute I 2040 er kanskje skipningssesongen økt til 150 dager, sammenlignet med 20-30 døgn ved århundre-skiftet Økt tilgjengelighet Nye folkerettsutfordringer Jon Ove Hagen Institutt for geofag, Universitetet i Oslo joh@geo.uio.no, Faculty of Mathematics and Natural Sciences Åpning av nye skipsruter har stor økonomiske implikasjon Havisutbredelse i 2008 og 2009 September 1979-2008 IPY GLACIODYN The dynamic response of Arctic glaciers to global warming Breene er sensible for små endringer i klimaet Trend: -11,7% per tiår September 08 Desember 08 Kronebreeen, Svalbard Photo: Monica Sund 1
Massebalanse - volumendringer Mother earth is crying M/ t = M a - M m - M c ± M b Where Ma = accumulation, Mm = melting, Mc = calving and Mb = bottom melt/freeze Breenes masse-endringer i et varmere klima 1. Overflatesmelting økt avrenning 2. Dynamiske endringer økt glidning og mer kalving Økt massetap fra land til hav Havnivåendringer Impacts of glaciers in a warmer climate: Increased fresh water flux to fjords and oceans: Global Sea level THC - Thermohaline circulation Regional Oceanographic impacts on circulation pattern sea ice formation Increased sediment and nutrients natural and anthropogenic (pollution) marine biology - fish, animals, plants Water balance in basins water supply, hydro power 2
Global Thermohaline Circulation Hva påvirker havnivået? Termisk utvidelse av havet Land-baserte ismasser (isbreene) Antarktis Grønland Breer og iskapper Grunnvann, permafrost, kunstige magasiner Modeled mean global sea level rise is 0.09 to 0.88 m until 2100 (IPCC, 2001) IPCC 2007: 0.18 to 0.59 (but with large regional variations!) Regionale trender i middel havnivåendringer (mm yr 1 ) for 1955 til 2003 (Church et al., 2004) 3
Sea-level transgression scenarios for Bangladesh (17 % of the country is below 1 m a.s.l.) Globale havnivåendringer siste 140 000 år Adapted from Milliman et al. (1989). Grønland - temperaturutvikling siste 100 000 år Sea level is rising now by 3.1 mm per year, double the average rate of the 20th century. Sea Level Rise: trends From UNEP 2007 4
Globale ismasser gitt i havnivå Glaciers and Sea level 70 60 50 40 30 20 10 0 m Glaciers and Ice caps (0,5 m) Volume sea level (m) Greenland (7,2 m) Antarctica (61,1 m) Volume (%) 100% = 28.4 M km 3 Antarctica 89.1 Glaciers 0.5 Greenland 10.5 Antarctica 61.1 Accumulation (%) 100% = 3083 Gt a -1 Glaciers 22.4 Greenland 20 Greenland 16.5 Current Sea Level Rise (%) 100% = 0.8 mm a -1 Antarctica 10 Comparison of total volume (left), total annual accumulation (middle), and total contribution to sea-level rise (right) for small glacier/ice caps and the ice sheets in Greenland and Antarctica Glaciers 70 Hvor er det isbreer utenom Grønland og Antarktis Hvordan måler vi endringene? Feltarbeid - Svalbard From Department Gregory of et geosciences al. (2001) 5
Selected glaciers: Simultaneous groundbased airborne and satellite data UNIVERSITY OF OSLO Fra satellitter Svalbard Vestfonna and Austfonna Ice caps Fra fly V A På breen Depot Austfonna Summit camp Isbjørnbesøk AWS Mass balance stake Area ~8120 km 2. Maximum elevation ~800 m a.s.l., max. ice thickness 560 m (Dowdeswell, 1986). Polythermal and situated below the percolation-zone. Simple dome-shape topography, large part is calving and several drainage basins are surge-type Department of (Hagen geosciences et al., 1993). 6
Stakemålinger Automatiske værstasjoner på Austfonna Riming er et problem Feltarbeid på Austfonna, Svalbard - iskjerner, GPS-målinger, radarmålinger 7
Høydeforandring relativt til 1936 (m). 10/6/2010 1930 1940 1950 1960 1970 1980 1990 2000 0-5 Glacier recession 1928 2002 (from NP and Greenpeace) 1928 Midtre Lovénbreen -10-15 -20-25 -30 2002 Midre Lovénbreen Ny-Ålesund Breforandringer from Jack Kohler, NP 1923 8
Cumulative mass balance Svalbard 1965-2005 Ny-Ålesund Midre Lovénbreen 1923 from Jack Kohler, NP Svalbard Minkende breer siden1920åra Stabil minking siden målingene startet i 1967 Men: Økt smelting etter 2000 på grunn av varmere og lengre sommersesong Cumulative glacier mass balance in mm SLE (Dyurgerov and Meier, 2005) Increased loss since mid 1990ies 9
Cumulative global mass balance 1945-2005 Observert globalt estimat av massebalanse period mm SLE a -1 1961-1990 + 0.38 0.19 1991-2004 + 0.77 0.26 Consensus estimate based on Ohmura (2004), Cogley (2005), Dyurgerov and Meier (2005) (compiled from Kaser et al. 2006) The above includes glaciers and ice caps in Greenland and Antarctica. NB- Large uncertainty of up to ca. 50 % Framtidig avrenning fra breer og iskapper Grønland 1. Smelting høyere opp på innlandsisen stor usikkerhet om avrenningen 2. Raske dynamiske endringer på mange brestrømmer etter 2000 - høyere glidning og mer kalving - dvs. Mer massetap 2000 2100 10
Greenland (ACIA, 2005) melt areas Increasing melt extent on the Greenland Ice Sheet Record melt extent in 2005 (Huff & Steffen, 2005) UNIVERSITY OF OSLO Greenland ice stream calving Triggering increased sea level? Grønland smeltearealet øker 11
Grønland brefrontene trekker seg tilbake raskere Jakobshavn isstrøm fronten går tilbake og den glir raskere After Weidick and NASA/Goddard Space Center Hvorfor glir breene raskere? Greenland mass balance Increased basal sliding: 1. More surface meltwater lubricate the bed 2. Less backpressure calving and bottom melting under the floating ice 3. Sea water temperature Krabill et al. 2000 IPCC 2007 - Alley (2007): H and B surface mass balance T-green (laser altimetry), Z-violet (radar altimetry), blue (GRACE gravity), R- red (SARinterferometry discharge+surface ) 12
Mass change on the Greenland ice sheet since 2003 Antarctica elevation changes (UNEP, 2007) Larsen Ice Shelf collapse Landsat TM, 01-03-86 MODIS Terra, 28-02-2005 Surging of upstream ice streams? From Cook and Vaughan, 2009 13
Total area of floating ice on the Antarctic Peninsula over the past 5 decades From Cook and Vaughan, 2009 From Cook Department and Vaughan, of geosciences 2009 Sea Level Rise (mm yr 1 ) G A Sea level rise 2006-2100 glacier contribution - including dynamic response (modified from Meier et al. 2007) 1961-2003 1993-2003 Thermal Expansion 0.42 ± 0.12 1.6 ± 0.5 Glaciers and Ice Caps 0.50 ± 0.18 0.77 ± 0.22 Greenland Ice Sheet 0.05 ± 0.12 0.21 ± 0.07 Antarctic Ice Sheet 0.14 ± 0.41 0.21 ± 0.35 Sum 1.1 ± 0.5 2.8 ± 0.7 Observed 1.8 ± 0.5 3.1 ± 0.7 Difference (Obs. Sum) 0.7 ± 0.7 0.3 ± 1.0 GIC Therm al exp. Obs. Glaciers and ice caps SLR 2006 mm/year 1.1 0.2 Greenland 0.5 0.1 Antarctica 0.2 0.1 2050 Total (mm) 49-81 43 22-65 28? 7-18 15 2100 Total (mm) 104-240 128 47-245 106 15-65 50 Total 1.8 0.5 78-164 65? 167-550 230 (From IPCC, 2007) 14
Modellert havnivåøkning - fra IPCC 2007 IPY GLACIODYN 2007-2010 The dynamic response of Arctic glaciers to global warming Økt kalving? - Breene reagerer både med mer smelting og mer kalving - Den dynamiske effekten er komplisert og usikker - Hvor raskt kan vi få endringer og hvor store blir de? Thank you! 15