Post on 29-Jan-2016
description
Jamie Morison
Polar Science Center, University of Washington
morison@apl.washington.edu
PresentationSEARCH Open Science Meeting
Seattle, WashingtonTuesday, October 28, 2003
SEARCH Vision and Core Hypotheses
SEARCH Motivation
“Axiom”The Arctic has been characterized in
recent decades by a complex of significant, interrelated, pan-Arctic
changes (Unaami).
Ice thickness decreased 42% in last 30 years (Rothrock et al, 1999)
Beaufort High decreased and shifted east in 1990s
Transpolar Drift of ice shifted axis counterclockwise producing a more cyclonic motion in 1990s
Ice extent decreased 3%/decade (Parkinson et al.)
Atmospheric Pressure and Ice Changes
Comparing the 1993 SCICEX data with the EWG climatology, we
see a salinity increase in the upper 200 m of the Makarov Basin,
indicating a shift in front between Atlantic and Pacific waters.
Ocean Salinity Change
From Morison, et al., , 2000, , Arctic, 53, 4.
Saltier Atlantic-Derived Water
Frontal Shift
Salinity Increase
Fresher Pacific-Derived Water
(from Brodeur et al., 1999)
Marine Ecosystem Change in 1990s
Brackish water sea-ice ecosystems
Whale migrations shifting with reduced ice extent
Barents Sea fisheries shifting north
Bering Sea jellyfish increase
Bering Sea phytoplankton blooms
Terrestrial Change - Increased Runoff
Over 64 years, discharge from the 6 largest Eurasian arctic rivers has increased 7% (128 km3/y or 0.004 Sv) [Petersen et al., Science 2002]
June Runoff Annual Runoff
Pavlov et al., 1998
Peterson, Bruce J. , Robert M. Holmes, James W. McClelland, Charles J. Vörösmarty, Richard B. Lammers, Alexander I. Shiklomanov, Igor A. Shiklomanov, and Stefan Rahmstorf, Increasing River Discharge to the Arctic Ocean, Science, December 13; 298: 2171-2173.
Terrestrial Change - Thawing of Frozen Ground
(from Osterkamp & Romanovsky, 1999)
Permafrost temperatures in the Russian Arctic and intermittent permafrost region of Alaska rising in the 90s.
Permafrost temperatures falling in eastern Canada.
1985T. Osterkamp photo1997 T. Osterkamp photo
Thermokarst formation - drainage changes
Highest Highest 1/31/3
Middle 1/3Middle 1/3 Lowest 1/3Lowest 1/3
High values in PC-1 correlated variables occur in recent years
1965 1975 1985 1995 Overland et al., Clim. Change, 2003
What’s Unaami you ask?Check out the Unaami Web site :http://www.unaami.noaa.gov and Jim’s Principal Component analysis.
Three Types of Arctic Change
(30 Years of Data) PC-1: Regime-like – Arctic Oscillation/NAO
1989 Shift PC-2: Interdecadal - High Arctic (P&J Index)
PC-3: Linear – Lower Arctic Land
SEARCH Hypothesis 1
Unaami is related to a spin up of the atmospheric Polar Vortex
(e.g., AO).
Connection to the Polar Vortex
Low pressure spins up Polar Vortex, brings warm air to Greenland Sea & Russian Arctic
Warm air over Greenland Sea allows warmer Atlantic Water in Arctic Ocean
Warm air advection increases SAT, warms permafrost
Increase in Polar Vortex- More cyclonic ocean circulation- Shift in front and Transpolar Drift - Russian shelf water to Beaufort
Increase in Polar Vortex- Increases open water- Decreases Albedo- Increases radiative heating & melt- Freshens upper Beaufort Sea
AO Index
1900 1920 1940 1960 1980 20001900 1920 1940 1960 1980 2000
Rising AO means lowers SAP over the Arctic.
Thompson and Wallace, 1998)
1950 1960 1970 1980 1990 2000 2010
-1.5
-1
-0.5
0
0.5
1
1.5
2AO Index (NDJFMA) 1950-2003 Relative to 1950 -88 Avg
AO update: Decreased in mid 90s but on average still high
Cyclonic Circulation
- Increases export of fresh water and sea ice- Decreases salinity and increases stratification of the sub-Arctic seas- Inhibits global ocean overturning
Does positive AO produce more cyclonic circulation?
- Gudkovich (1961)- Proshutinsky and Johnson (1997)- Zhang, Rothrock and Steele, 1998, Warming of the Arctic Ocean by a strengthened Atlantic inflow, GRL, 25, 1745-1748.
a) 1979 - 88
b) 1989 - 96
b) - a)
More Cyclonic
Shift in axis of front and surface current
Does high AO cause a frontal shift?
1973 LOW AO
Concentration of Atlantic Water tracer (%) averaged over depth of 180-560 m for repeated 1973 forcing (Maslowski et al, 2000)
1993 HIGH AO
Concentration of Atlantic Water tracer (%) averaged over depth of 180-560 m for repeated 1993 forcing (Maslowski et al., 2000)
Model Suggests: YesFrom: Furevik, Chapman Conference, 2002
SEARCH Hypothesis 2
Unaami is a component of climate change.
Spin up of the Polar Vortex as part of greenhouse warming response
(Shindell et al., 1999)
AO observations
EOF 1 in GHW simulation with stratosphere
(Fyfe et al.,1999)
1950 2000 2050 2100
GHW Simulation
GHW Simulation
GHW Simulation
Control Simulation
Observed -
earlier and larger than simulated
AO Index
SEARCH Hypothesis 3
Feedbacks among the ocean, the land, and the atmosphere are critical to
Unaami.
Zhang
Zhang, Rothrock and Steele, 2000, , J. Clim., 13, 3099-3114.
-0.5
-1.00.0
2.01.0
Simulated sea ice changes by Zhang et al. (2000) show shift in drift axis, increased drift speeds, increased lateral melt
(a) 1979 - 88 mean
These lead to reduced residence time, reduced average thickness in the basin, but
increased ice export from the Basin to the North Atlantic.
Ice Budget Differences in the Basin*(89 to 96) - (79 to 88)Vert. Growth 0.0Lateral Melt - 0.6Export - 0.7Ice Production -1.3
* (1012 m3 yr-1)
(b) 1989 - 96 mean
(c) = (b) - (a) UnaamiAffects Albedo
Affects Global THC
entire system undergone freshening
Unaami’s increased runoff, change in Pacific water circulation, and increased ice production may be manifest in a general freshening of the entire system of overflow and entrainment that ventilates the deep Atlantic.
Dickson et al 2002
Borrowing from Bob Dickson’s talk tomorrow:
The Polar Vortex Responds to Arctic Change
A simulated atmospheric response to a change in Labrador Sea ice cover from minimum to maximum produces a shift in NAOmodel of -0.7 Std.
Changes in ice cover feedback on hemispheric circulation of the
atmosphere
&
snow in Seattle, temperature in Washington D.C., etc.
Simulated difference in long-term JFM 1000 hPa height (m) between max ice extent and minimum ice extent in the Labrador Sea
Kvamtso, Skeie, and Stephenson, 2003, accepted, Int. J.of Climatology
+40
-20
SEARCH Hypothesis 4
The physical changes of Unaami have large impacts on the Arctic ecosystems and society.
Human Dimension of Change
Ice extent, thickness, and duration are reduced, hurting transportation and subsistence
43% decrease in sea ice thickness (Rothrock et al. (1999)
From Alaska Native Science Commission and Institute of Social and Economic Research, Alaska Traditional Knowledge and Native Foods Database, http://www.native knowledge.org
Changes in climate raises concern about native foods
Inland precipitation changes cause drying affecting food gathering
Increases in fire frequency in Alaska over the past 50 years (Oechel and Vourlitis, 1996)
Increase in the abundance of woody shrub species and slow northward movement of treeline have major impacts on winter snow accumulation and soil temperature (Sturm et al., 2001),
Decreased ice extent & changes in storm patterns produce higher seas that accelerate coastal erosion
Enhanced cyclonic ocean circulation raises coastal sea level (Proshutinsky and Johnson, 1997)
Weather is more unpredictable affecting safety, food gathering, and transportation
Increases in cyclone activity north of 65°N since at least 1958 (Serreze et al., 2000)
Can the SEARCH paradigm help deal with change?
Example
Rigor et al. (2002) find a negative correlation between winter AO index and ice extent the following fall. This suggests that ….
Six month ice condition “outlooks” are possible!
http://iabp.apl.washington.edu/SeaIceAO/
Can the SEARCH paradigm help deal with change?
Example
Griffith et al. (2002) find a negative correlation between winter AO index and growth of the Porcupine Caribou herd. This suggests …
We can and should account for natural climate variations in discussions wildlife management in general and of
ANWR specifically.
To test these hypotheses and help society deal with change…
requires a program long-term, large-scale observations (including retrospective and paleo studies), analysis, and modeling —SEARCH.
Ocean Temperature Changes
§Comparing the 1993 SCICEX data with the EWG climatology, we see warm
cores over ridges indicating a shoaling and 1.5° warming of the temperature
maximum where the Atlantic Water inflow subducts to spread through the
Eurasian basin.
Atlantic Water 1.5° warmer
From Morison, et al., , 2000, , Arctic, 53, 4.
Conditions at the North Pole
EWG: 0.5° AW core at 350 m & 31 o/oo surface salinity 1990s: 1.5° AW core @ 250 m & 32.5 o/oo surface salinity
2000-02: AW temp slightly less than 1995 max Surface salinity < 1990’s
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030 31 32 33 34 35-2 -1 0 1 2
Salinity — North Pole 1950–2001 — Temperature (°C)
EWG Climatology,1950s, 60s, 70s, 80s
Oden ‘91,SCICEX, ’93-’99
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Salinity — North Pole 1950–2001 — Temperature (°C)
200288° 30' N71° 14' E
NPEO 2000 2001 2002
2003
2003: Atlantic Water slightly fresher
Variations in Global Temperature and their uncertainties,1861- April 2001(land air and sea surface temperature)
The context (i): during the past century, the global mean temperature has increased in two main episodes of warming
When we plot air temperature as a function of latitude and time, two things become clear: 1) the World is warmer. Including 2002, all ten of the warmest years since records began in 1861 have occurred since 1990; Jones and Moberg, 2003. 2) in the last two decades the distribution of warming has become global.
Courtesy Tom Delworth, GFDL
…and Karcher et al have pieced together the spread of warming around the boundary of the Arctic Ocean ……in 1980, 1984, 1987 & 1991,
from Karcher et al 2003.
… and its continued spread in 1993, 1995, 1996 & 1999,
from Karcher et al 2003.