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Greenland Synthesis project, SASS Seattle meeting 3/06
- Objectives:1) an estimate of the large temporal variations in fresh water output from land-based ice in Greenland 2) an improved understanding of the variability of the ice discharge flux from the Greenland Ice Sheet3) use 1 and 2 to investigate to what extent ice discharge variability from Greenland outlet glaciers is attributable to short term climate variability (e.g., through enhanced basal lubrication from surface melt)
Collaborative Research: A synthesis of rapid meltwater and ice discharge changes: large forcings from the ice with impacts on global sea level and North Atlantic freshwater budgets
Greenland Synthesis project, SASS Seattle meeting 3/06
The Greenland Ice Sheet in 3D (vertical exaggeration just about right for a glaciologist)
Greenland Synthesis project, SASS Seattle meeting 3/06
Topography of the Earthat high latitudes, the climate system is at least as effective as plate
tectonics in producing high elevation topography, and it does it quicker (both on the way up and the way down)
If you take fresh water out of the ocean, you have to pile it up somewhere. That growing or shrinking pile is part of the climate system. What are the feedbacks here? What can make the pile shrink the fastest? Is that going on now?
Greenland Synthesis project, SASS Seattle meeting 3/06
Greenland:
Melt and runoff
Ice flow and calving
Antarctica:
Ice flow and calving
Greenland Synthesis project, SASS Seattle meeting 3/06
- Objectives:1) an estimate of the large temporal variations in melt water output from land-based ice in Greenland 2) an improved understanding of the variability of the ice discharge flux from the Greenland Ice Sheet3) use 1 and 2 to investigate to what extent ice discharge variability from Greenland outlet glaciers is attributable to short term climate variability (e.g., through enhanced basal lubrication from surface melt)
Collaborative Research: A synthesis of rapid meltwater and ice discharge changes: large forcings from the ice with impacts on global sea level and North Atlantic freshwater budgets
Greenland Synthesis project, SASS Seattle meeting 3/06
First #2 (#1 has more ties to the other SASS projects, so we will spend more time on it)
2) an improved understanding of the variability of the ice discharge flux from the Greenland Ice Sheet• Driving questions: How has glacier terminus
position and ice thickness varied over the last 100+ years, to the extent that it has been documented? How do present rapid changes compare in this context? How do processes near the termini of glaciers reflect changing climate conditions and/or connections to oceanographic processes?
• Inputs: existing observations (historical, satellite-based, direct measurements of speed up and thinning), models, characterizations of outlet glaciers (condition of calving faces, change in front configuration compared to older observations, present drawdown rates), and understanding of ice discharge processes (position in the tidewater glacier cycle); outputs -> constraints on the variability of ice flow contributions to the fresh water output from the ice sheet
Greenland Synthesis project, SASS Seattle meeting 3/06
Left out of the last figure is the complexity introduced by the tidewater character of all major outlet glaciers
in Greenland
The tidewater glacier cycle as first described by Austin Post: (tidewater glaciers are those terminating in the ocean)
1) Slow advance of the ice front down the fjord, as the glacier moves a stabilizing moraine shoal ahead of it along the bottom - the longer the low elevation part of the glacier gets, the more susceptible it becomes to warm periods
2) A period where the terminus remains in an extended position against the shoal
3) Rapid retreat after a thinning glacier backs off of the moraine shoal; this retreat can pause or reverse if conditions or geometry favor stability
Greenland Synthesis project, SASS Seattle meeting 3/06
Greenland Synthesis project, SASS Seattle meeting 3/06
Greenland Synthesis project, SASS Seattle meeting 3/06
1) an estimate of the large temporal variations in melt water output from land-based ice in Greenland
• Driving question: What is the spatial and temporal variability in Greenland Ice Sheet surface melt and runoff over the past 125+ years?
• Inputs: ice-core records of melt, coastal station and on-ice meteorological records, glacier survey data (snow pits, ablation stakes), remote sensing, and output from multi-decadal regional and global climate analyses; outputs -> the longest possible reconstruction of estimated surface mass balance, melt and runoff from the inland ice.
Greenland Synthesis project, SASS Seattle meeting 3/06
Ice (& Firn) Core Records of Melt Amount
Sarah Das
WHOI
Greenland Synthesis project, SASS Seattle meeting 3/06
0
5
10
15
20
25
1675 1700 1725 1750 1775 1800 1825 1850 1875 1900 1925 1950 1975 2000
D5 Melt 10y
Das1 10y
B9 10y
B2 10y
B6 10y
B7 10y
Das2 10y
D4 10y
D5: C-2473m
Das1: SC-2497m
B2: SW-2226m
D4:C-2731m
Das2: SE-2936m
B9: S-2713m
B6, B7: SE-2439m
10-yr running average melt amount(recent record shows 20yr trends between all sites)
Me
lt (t
ota
l cm
of i
ce/y
ear)
Greenland Synthesis project, SASS Seattle meeting 3/06
0
5
10
15
20
25
1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000
D5 Melt 10y
Das1 10y
B9 10y
B2 10y
B6 10y
B7 10y
Das2 10y
D4 10y
20y cyclesCorrelation between melt and decadal cycles of NAO/AO
1y, 10y NAO (IPCC 2001)
Melt (total cm)
Greenland Synthesis project, SASS Seattle meeting 3/06
Instrumental period 1983-2002Interannual Melt Highly Variable
0
20
40
60
80
100
120
140
20022001200019991998199719961995199419931992199119901989198819871986198519841983
D5 melt
Meltsite2
Meltsite1
Basin9 Melt
Basin8 Melt
Basin7 Melt
Basin6 Melt
Basin2 Melt
Basin1 Melt
PinatuboEl Chichon
Melt (total cm)
Greenland Synthesis project, SASS Seattle meeting 3/06
Greenland Ice Core Melt Stratigraphy Records CoreSite - previously analyzedCoreSite - analyzed Jan 2006
Core Site Depth (m) Age Lat (°N) Lon (°E) Elev (m)B1 19.87 1976-2002 71.80 317.56 2904B2 16.88 1980-2002 68.32 315.17 2226B6 24.54 1983-2002 66.96 318.25B7 24.47 1983-2002 67.52 319.59 2439B8 30.07 1958-2002 69.84 323.60 2988B9 30.11 1957-2002 65.01 315.13 2713D4 145.43 1738-2002 71.42 315.97 2731D5 148.10 1675-2002 68.50 317.10 2473Das1 83.35 1908-2002 66.00 316.01 2497Das2 83.97 1936-2002 67.53 323.94 2936ACT1 29.71 (not yet dated) TBD 66.00 313.45 2179ACT2 113.77 1770-2004 66.01 314.99 2412ACT3 144.66 (top 73 m dated) <1934-2004 66.00 316.39 2510ACT4 36.14 1979-2004 65.98 317.21 2345Katie 29.98 1934-2004 Summit 3209
Additional core stragraphy analyzed for ARCSS - 354.22 m
Greenland Synthesis project, SASS Seattle meeting 3/06
Instrumental-era Greenland Temperature and Ice Sheet
Runoff Reconstructions
J. E. Box
Byrd Polar Research Center
Synthesis of Arctic System Science (SASS) Synthesis of Arctic System Science (SASS) Investigator MeetingInvestigator Meeting26–27 March 200626–27 March 2006
Seattle, WashingtonSeattle, Washington
Greenland Synthesis project, SASS Seattle meeting 3/06
Surface Air Temperature Data• Coastal temperature records
– Nuuk• Seasonal (1873-2001) and Annual (1873-2004)
– Tasiilaq • Seasonal (1895-2001) and Annual (1873-2004)
– Thule• Seasonal and Annual (1947-present)
– Narsarssuaq• Seasonal (1961-present) and Annual (1873-2004)
– Aasiaat• Seasonal and Annual (1951-present)
– Danmarkshavn (1951-present)• Seasonal (1951-2001) and Annual (1948-2004)
• Polar MM5 – 24 km grid – currently 1988-2005– (by Feb. 2006) 1958-2005
Greenland Synthesis project, SASS Seattle meeting 3/06
Methodology• Correlate time series from each coastal station records
with time series of each Polar MM5 grid cell– Training period
• currently 1988-2005, (N = 18)• (by Feb. 2006) 1958-2005, (N = 48)
• Rank top two sites for each grid cell based on correlation• Store linear regression coefficients (slope and intercept)
for the top two ranked sites on pixel by pixel basis– Only store coefficients if above significance threshold
• Use full record to reconstruct seasonal ice sheet temperatures– 1873-2004 available for annual means, (N = 132)
Greenland Synthesis project, SASS Seattle meeting 3/06
Regions of Maximum Correlation
Annual
Greenland Synthesis project, SASS Seattle meeting 3/06
Highest Rank (Primary)2nd Highest Rank (Secondary)
Dominant Annual Correlations
Greenland Synthesis project, SASS Seattle meeting 3/06
Thul Uper Ilul Nuuk Nars Danm Tasi
Primary 0.06 0.06 0.49 0.15 0.02 0.07 0.13
Secondary 0.10 0.04 0.21 0.46 0.14 0.01 0.01
Overall 0.08 0.05 0.70 0.31 0.08 0.04 0.07
Ilulissat and Nuuk dominate the annual variance
Results of Annual TrainingFraction of grid ‘belonging to’ each site
Greenland Synthesis project, SASS Seattle meeting 3/06
Annual Training Conclusions
• Iulissat and Nuuk temperatures are better linked with overall ice sheet temperature variability than other sites
• Tasiilaq and Upernavik variability represents maritime locations better than terrestrial locations
Greenland Synthesis project, SASS Seattle meeting 3/06
Annual Reconstruction
Greenland Synthesis project, SASS Seattle meeting 3/06
1873-20041873-2004 mean: mean: -21.89 C-21.89 C
Greenland Synthesis project, SASS Seattle meeting 3/06
Linear Trend: +0.045 C/ decadeLinear Trend: +0.045 C/ decade, 0.6 K increase over 132 years0.6 K increase over 132 years, r r =0.380=0.380
Greenland Synthesis project, SASS Seattle meeting 3/06
1873-2004 mean: 1873-2004 mean: -13.16 C -13.16 C Linear Trend:Linear Trend: ++0.0530.053 C/ decade, 0.7 K increase over 132 years, C/ decade, 0.7 K increase over 132 years,
r = 0.472r = 0.472
Greenland Synthesis project, SASS Seattle meeting 3/06
Climatological Conclusions
• Linear model explains < 2/5 of variance
• Inter-decadal oscillations?
• Warming 0.6 C overall, 0.7 C below 1200 m elevation
• 2003 warmest on record, 1883 coldest
Greenland Synthesis project, SASS Seattle meeting 3/06
Seasonal Correlations
Seasonal
Greenland Synthesis project, SASS Seattle meeting 3/06
Primary Secondary
Dominant Seasonal Correlations
Greenland Synthesis project, SASS Seattle meeting 3/06
Primary Secondary
Dominant Seasonal Correlations
Greenland Synthesis project, SASS Seattle meeting 3/06
Primary Secondary
Dominant Seasonal Correlations
Greenland Synthesis project, SASS Seattle meeting 3/06
Primary Secondary
Dominant Seasonal Correlations
Greenland Synthesis project, SASS Seattle meeting 3/06
Seasonal Training Conclusions
• Need to obtain longer seasonal records– Ilulissat– Narsarssuaq– Ivigtut
• Nuuk series not useful to reconstruct winter temperatures– Nuuk winter temperatures never register as
primary maximum correlator, hardly as secondary correlator
Greenland Synthesis project, SASS Seattle meeting 3/06
Reconstruction Results
Seasonal
Greenland Synthesis project, SASS Seattle meeting 3/06
Greenland Synthesis project, SASS Seattle meeting 3/06
Runoff Reconstruction
Greenland Synthesis project, SASS Seattle meeting 3/06
Greenland Synthesis project, SASS Seattle meeting 3/06
3) use 1 and 2 to investigate to what extent ice discharge variability from
Greenland outlet glaciers is attributable to short term climate variability (e.g., through enhanced basal lubrication from
surface melt)
Greenland Synthesis project, SASS Seattle meeting 3/06
Researchers:
Ice flow/change:
Mark Fahnestock, UNH, Ice flow and surface melt, RS of large ice sheets
Martin Truffer, UAF, Ice flow (field and modeling) - outlet glaciers
Ian Joughin, APL/UW, Ice flow - RS of large ice sheets and modeling
Byron Parizek, PSU, Ice flow modeling of large ice sheets
Melt/change:
Richard Alley, PSU, ice sheets and climate
Sarah Das, WHOI, ice core records of melt, RS of melt
Jason Box, BPRC/OSU, Polar meteorology/met stations/Atm modeling
David Rausch, PSU, ice sheet/climate connections, tools for data analysis
(Overlaps and connections between these two groups omitted for simplicity)
Greenland Synthesis project, SASS Seattle meeting 3/06
End of slideshow
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