DARGAN M. W. FRIERSON DEPARTMENT OF ATMOSPHERIC SCIENCES 11/20/2013 ATM S 587: Fundamentals of Climate Change! sea ice! continental ice sheets! permafrost! mountain glaciers! snow cover! !The cryosphere!ice caps!The Cryosphere in Present Day ! Cryosphere: frozen water in the climate ¡ Mountain glaciers: permanent ice on top of mountains ¡ Ice sheets: glaciers that cover a large amount of land ÷ Currently only Greenland and Antarctica ¡ Seasonal snow cover ¡ Sea ice: frozen ocean water floating ¡ Permafrost: frozen soilRelative Sizes of Cryosphere ! Cryospheric components: ÷ In terms of coverage area (percent of Earth surface area) and volume (how much sea level rise (SLR) would result from melting it all) ¡ Antarctic ice sheet: 2.7% of Earth surface area, 61.1 meters of sea level rise (SLR) if melted ¡ Greenland ice sheet: 0.35% of area, 7.2 meters of SLR ¡ Alpine glaciers: 0.01% of area, 0.2 m of SLR ¡ Seasonal snow cover: 9% of area (maximum), <0.01 m of SLR ¡ Permafrost: 5% of area, 1 m of SLR ¡ Sea ice: 7% of area (in season of maximum extent), 0.01 m of equivalent mass, (no sea level rise when sea ice melts)Northern Hemisphere Cryosphere ! Maximum extent of ice types in NH: (snow extent here is where snow coverage is > 50% during month with max coverage)Sea iceSea Ice ! Forms from frozen ocean water ¡ Not the same as icebergs, which break off of land ice ! Floats on the ocean surface ! Grows over the winter, melts in the summerIce shelf!Icebergs!Sea Ice!Iceberg!An exception is in pressure !ridges which form when sea ice !bumps into other sea ice. These !can be 10-30 m thick!Arctic Sea Ice is typically 0.5 !to 3 m thick!How thick is sea ice?A scientific research team on sea iceSea Ice Seasonal Cycle ! NH and SH seasonal cyclesMelting Sea Ice ! Recent summer Arctic sea ice coverage is 30% lower than 30 years ago Ice always grows back in the winter (when there’s no sunlight and it’s extremely cold) Minimum ice coverage occurs in September Especially 2007 was an extremely anomalous year, as was 2012 (not plotted)September Minimum Ice Extent ! Last 7 yrs: seven lowest years in Arctic sea ice extent Average September coverage from 1979-2000 in pinkAnimation of September Sea Ice Coverage ! Each year’s minimum sea ice extent since 1979Winter Sea Ice ! Sea ice is getting younger à and thinner as well ¡ Almost no ice is left that’s over two years old What do climate models say about the future of sea ice?UW Research (Prof. Cecilia Bitz)Future of Arctic Sea Ice ! Ice is getting younger and thinner ! Many models predict disappearance of summer ice by 2060 ¡ Previous slide’s research of Prof. Bitz ! What will the impacts of the sea ice loss be? UW Prof Cecilia BitzProjected summer shipping routes!Antarctic Sea Ice Trends ! Not much trend in S. Hem. (slight increase actually) ¡ Related to ozone depletion? (Turner et al 2009)How does sea ice loss affect climate? ! Ice-albedo feedback amplifies warming ! Warming reduces pole-to-equator temperature gradient, meaning heat is drawn less towards pole and lower latitudes warm more tooWhat are other impacts of sea ice loss? ! Erosion if sea ice disappears (it damps waves) ¡ Thawing permafrost also causes surfaces to soften ! Fragile and specialized ecosystemsRinged Seal Nests ! Need 50 cm of snow drifts to build nests for their youngRecent Study on Snow on Sea Ice More snowfall in winter in the future But shorter-lived sea ice leads to less snow depth on ice Bad news for seals… From new paper by Hezel, Zhang, Bitz and KellySummary of Sea Ice ! Sea ice is melting rapidly in the Arctic ! Dangerous for animal habitats there ¡ Polar bears ¡ Ringed seals ! Coastal erosion enhanced nearby ! On the plus side, if the climate stops warming, sea ice stops receding ! And sea ice melting doesn’t lead to sea level rise ¡ Land ice melting does affect sea level – let’s discuss that nextWhat about land ice? There are two ice sheets in the world: Greenland: 7 meters sea level equivalent Antarctica: 61 meters sea level equivalent The Arctic is changing most rapidly, so let’s start with Greenland… Land ice loss causes sea level rise…Sea Level of the Past ! Last Glacial Maximum (15,000 yrs ago): 120 meters lower sea level! ! Cretaceous (100 mil yrs ago): >100 meters higher! Last Glacial Maximum Present Ice sheet extent The Cretaceous SeawayPredictions of Sea Level Rise vs Past Changes ! Last time the temperature was 3o C warmer, sea level was 30 meters higher… Sea levels have varied a huge amount in the past! This is not even close to what’s predicted though We’ll talk about why, and whether more extreme changes are possibleGreenland Ice Sheet ! Greenland: ice is ~100,000 yrs old ¡ Surface is depressed to approximately sea level in the middle, mountains on the perimeter ¡ Loses mass from sublimation, calving of icebergs away from edges, & running off of meltwater ¡ Gains mass by snowfall ¡ Large temperature rise in Arctic means melting has outweighed increased snowfall recently Greenland summit is approximately height of Mount BakerMass balance of an ice sheet!Gains mass from snow on top Loses mass from melting and calving of icebergs Both loss and gain are increasing (increased precipitation at high latitudes) Greenland is losing mass though (losses are bigger than gains)…Future of Greenland Ice Sheet ! Arctic is ground zero for global warming – what will happen to Greenland ice sheet? ¡ Melt area has been expanding in recent years ¡ Ice sheet models indicate 3 C warming would lead to 1 m sea level rise over 1000 yrsMelting has increased since we’ve been measuringIce shelf!Glacier calving:!breaking of ice to form !icebergs!!A natural process!but terminus of many!glaciers is retreating!Where in Greenland does "most of the calving of !icebergs occur? !Greenland is surrounded by fjords filled with ice streams (fast flowing ice) Many icebergs calve within these streamsGreenland Ice Loss from Calving ! 10% of Greenland icebergs calve from Jakobshavn Isbrae ¡ You might know it as Sermeq Kujalleq ¡ Don’t confuse with Kangerdlugssuaq ¡ Near town of