THE UNRAVELING OF THE ARCTIC: GLACIERS MARTIN SHARP, UNIVERSITY OF ALBERTA CCF: EARTH DAY 2015 GLACIERS IN THE ARCTIC LOW ARCTIC HIGH ARCTIC MAJOR REGIONS HIGH ARCTIC GREENLAND ARCTIC CANADA SVALBARD RUSSIAN ARCTIC ISLANDS LOW ARCTIC ALASKA/YUKON NORTHERN SCANDINAVIA ICELAND CLIMATIC CONTEXT SUMMER AIR TEMPERATURE (°C) WINTER PRECIPITATION (mm/day) WHY DO GLACIERS MATTER ? •  Glacier mass change is a first order control on global mean sea level •  Glacier changes (albedo, surface temperature, topography) cause feedbacks on global/regional climate •  Hydropower potenRal (Yukon/Alaska/Scandinavia/
Greenland/Iceland) •  Legacy pollutants (e.g. trace metals, organic pollutants, black carbon stored in ice) •  Marine biogeochemistry (nutrient-­‐rich meltwaters sDmulate biological producDvity and sustain food supply for seabirds and marine mammals) CAUSES OF GLACIER CHANGE •  Air temperature changes (affect melt rates) •  Changes in snowfall •  Changes in ocean temperatures (maGer for glaciers that terminate in the ocean) •  Changes in ice dynamics/rates of iceberg calving into the ocean HOW DO GLACIERS CHANGE? •  AREA •  THICKNESS •  VOLUME •  MASS Yukon 1958-­‐1960: 11,622 km2 2006-­‐2008: 9,081 km2 Area Loss: 2,541 km2 (= 22% of 1958-­‐60 Area) Only 4 glaciers grew in area Source: Barrand and Sharp, 2010 CLIMATIC MASS BALANCE (CMB) •  ANNUAL SNOWFALL MINUS ANNUAL RUNOFF •  Measured on the ground annually at up to 28 glaciers across the Arc6c since 1946 •  Number of glaciers measured varies over 6me •  NOTE: RUNOFF ≠ TOTAL MELT •  At higher eleva6ons some frac6on of melt drains down into the snow pack and firn layer and refreezes, so is retained within the glacier (internal accumula6on) •  This frac6on may change as climate changes OBSERVED ARCTIC ANNUAL MEAN CLIMATIC MASS BALANCES REGIONAL CUMULATIVE CLIMATIC MASS BALANCES OTHER SUPPORTING EVIDENCE: ICE SURFACE TEMPERATURE CHANGE (Melt Season Mean T (°C)) Marie-­‐Laure Geai ICEBERG CALVING •  ADDS TO MASS CLIMATIC MASS BALANCE •  INFLUENCED BY ICE DYNAMICS AND CHANGES IN THE MARINE ENVIRONMENT QUEEN ELIZABETH ISLANDS: ICEBERG CALVING FLUXES WINTER 2012 •  Iden6fy major sources •  Quan6fy local and total fluxes (~ 2.6 Gt/yr) •  Need to know annual fluxes and their longer-­‐term variability and trends •  How important is calving? Wesley VanWychen (UOGawa) CAN MEASURE CHANGES IN TOTAL MASS Satellite Gravimetry (GRACE) 2003-­‐2014 360 Gt=1mm SLR
- ~700 Gt
- ~550 Gt
Bert Wouters (U.Bristol) GRACE OVER GREENLAND - ~3100 Gt
WHY THE FASTER LOSS SINCE THE MID-­‐1990s? CLEAR SUMMER WARMING Change in Mean Summer T (°C) ACCELERATED SUMMER WARMING SINCE 2005 -­‐ ESPECIALLY IN ARCTIC CANADA Change in Mean Summer T (°C) POTENTIAL FEEDBACKS MODIS summer minimum albedo: 2000 -­‐ 2012 2000 2007 2001 2002 2003 2008 2009 2010 2004 2011 2005 2012 2006 Albedo trend: 2000-­‐2012 POSSIBLE CAUSES OF GLACIER ALBEDO DECREASE •  Darkening means surface absorbs more solar energy – and thus melts more rapidly •  Why does darkening occur? •  Warmer climate – (i) snow metamorphoses faster; (ii) snow disappears sooner, exposing ice earlier/longer •  Dust/black carbon – more deposiDon (forest fires, tundra fires, dust storms?) or faster melt-­‐out from snow •  Surface biology – more microbial blooms (dark pigmented algae) on snow/ice surfaces Marek SDbal, Marion Yallop Feedbacks from Changes in Firn Properaes •  Firn is snow en route to becoming glacier ice •  Denser than snow, less dense than ice •  Forms by compac6on and by refreezing of meltwater that percolates down into it during the melt season •  There is typically a layer of firn up to tens of m thick at higher elevaDons on the surface of glaciers/ice caps •  Do firn changes due to climate warming reduce runoff (if percolaDng water re-­‐freezes) or promote it (if refreezing fills pore volume and then prevents deep percolaDon) ? ICE BUILD-­‐UP IN FIRN ON DEVON ICE CAP 2004-­‐2012 Peter Bezeau LONGER TERM PERSPECTIVE (1000 – 11000 yrs) Fisher et al., 2012 Global and Planetary Change
CONCLUSIONS •  Glaciers in most regions of ArcDc losing mass over
period of record •  Rates of loss acceleraang since 1990s •  Linked to strong summer warming (longer melt
season, higher melt rates N.B. ArcDc Canada) •  Enhanced by posiave feedbacks involving
decreases in summer surface albedo (higher melt
rates) and ice layer buildup in firn (less deep
percolaDon of meltwater, more surface runoff) •  Iceberg calving remains a wild card ISSUES AND RESPONSES •  The fundamental issue is climate warming and sea
level rise – others are second order •  The impacts are global, not local to the ArcDc or
Canada – responses need to reflect this •  We need to slow or stop warming if we want to
minimize or avoid these impacts – the responsibility
to do so extends beyond our borders •  AlternaDvely, we need to prepare (and budget) to
miDgate the impacts •  Insurability may become a driver for acDon