Post on 15-Aug-2018
North Atlantic warming, disappearing sea ice and winter cooling
Vladimir A. Alexeev, International Arctic Research Center, UAF
with contributions from V. Ivanov, R. Kwok, I.Ezau,
J.Cohen, J.Furtado, M.Barlow
Geography of IARC schools
Fairbanks, AK
Toolik Lake, AK Barrow, AK McCarthy, AK
Fedorovskoe, Russia Arc�c Ocean Bellingshausen,
Antarc�ca
First summer school, July 2003
Geography of IARC schools
Map with locations of summer schools (red markers) and (incomplete!) locations of origins of attending students (blue markers).
2010: King George Island, Bellingshausen sta�on
in collabora�on with APECS, RAE, RAS, AWI, AARI, IAP
Scope
Focus on the Arc�c (and sub-‐polar regions) Climate system perspec�ve
Depending on loca�on, some�mes more focus on one of the components Students get involved in hands-‐on ac�vi�es
(seeing is believing)
Sea ice extent
ocean heat content (delayed freeze up)
Surface-based mechanisms are the most likely contributors to the recent Arctic warming in the summer and fall
Fate of Early 2000s Century Arctic Warm Water Pulse
By I.Polyakov, V.Alexeev, I.Ashik, S. Bacon, A.Beszczynska-Möller, E.Carmack, I.Dmitrenko, L.Fortier, J.-C.Gascard, E.Hansen, J.Hölemann, V.Ivanov, T.Kikuchi, S.Kirillov, Y-D.Lenn, F.A.McLaughlin, J.Piechura, I.Repina, L.Timokhov, W.Walczowski , and R.Woodgate
Bull. Of the Amer Met Soc, 2011
Water temperature (ºC) distribution, Laptev Sea, Sep 2013
At cross-slope section along 90ºE)
Thick (up to 50 m) warm surface layer, which almost merges with intermediate Atlantic water layer
http://www.ijis.iarc.uaf.edu
Atlantic Water and arctic sea ice. Winter
Alexeev et al, 2013, submitted
March 2012
Scoresby, W. 1820. An account of the Arctic regions with a history and description of the Northern whale fishery, (PhD Thesis by S.H.Teigen)
2004 2008
Fraction of multi-year ice
1
0
0 100 200 300 400 500
5 4 3 2 1 0 -1 -2
2004 2006 2008
Alexeev et al, 2013
AW temperature. Fram Strait and Svalbard
March-April 2005
March-April 2006
February-March 2008
Winter sea ice thickness. Atlantic sector
Thinning of ice is local Alexeev et al, 2013
Ice thickness and motion vectors, ICESat Ivanov et al, 2012, Alexeev et al 2013
Meridional wind
DLW (contours) snow anomalies Feb-Mar2008
Ice concentration anomaly
0
0.2
0.4
0.6
2004 2005 2006 2007 2008
How much ice does AW melt?
Explains at least 20% of the negative 2004-08 trend (volume-wise)
Alexeev et al, 2013
Winter temperature anomalies, NCEP/ NCAR Reanalysis data set
2010 2011
2012 Cohen, Barlow, Furtado, Alexeev, Cherry, 2012, ERL
% %
%%%
% %
%%%
% %
%%%
% %
%%%
DJF Trend = 0.07°C/10 yr
MAM Trend = 0.39°C/10 yr**
JJA Trend = 0.38°C/10 yr**
SON Trend = 0.49°C/10 yr**
1990 1995 2000 2005 2010
Time - [year]
[°C
]
0
1
2
0
1
2
0
1
2
0
1
2
[°C
]
[°C]
[°C]
**p < 0.01
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$$
$
$ $
0 1-1
[°C per 10 years]
(a) (b)
(c)
(d)
(e)
Northern Hemisphere Land Temperatures 1987-2010
Data: CRU temperature Alexeev et al, 2012, Clim Change; Cohen et al, 2012, ERL
Arctic Trends 1988-2010
2
% %
%%
%
% %
%
#
% %
%%%
6
7
# # # # # #
% %
%%
%
% %
%%
A
B
C
D
E
0
1
-1
[°C
]
0.35
0.45
0.25
[Frac. Area]
12
8
[106 km
2]
7
6
[kg
m-2
]
2
0
-2
[std
]
1990 1995 2000 2005 2010Time - [year]
5
JAS Arctic-MeanTemperature Anomaly
September ArcticSea Ice Coverage
Fall Arctic-Mean Lower Tropospheric Moisture
October EurasianSnow Cover
DJF AO Index
Trend = 0.44°C/10 yr**
Trend = -0.05/10 yr**
Trend = 1.46x106 km2/10 yr**Trend = -0.29x106 km2/10 yr**
Trend = 0.54 kg m-2/10 yr**
Trend = -1.0 std/10 yr** ** p < 0.01
Obs
CMIP5 Ens Mean
Warming Arctic
Less sea ice
More atmospheric moisture
Increasing snow cover
Decreasing Arctic Oscillation trend
Alexeev et al, 2005, Clim Dyn; Cohen et al, 2012, ERL
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!
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!
Negative Phase of the Arctic Oscillation
[hPa]
!
"
#
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#
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!
Tropospheric Winter Trends
Trend in SLP and zonal wind at 10m (ERA-Interim)
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!U 10m
Changes in January surface air temperature. The Arctic becomes warmer by up to 40°° C but the latitudinal belt south of 60°°N over land becomes colder by up to 8°°C. Newson 1973;
Nature, 241, 39-40
One of the first UKMO GCM sensitivity experiments with polar ice replaced by water at 0°°C
Description of the Numerical Model
- Upper mixed layer ocean coupled to a full 3D atmospheric GCM
- Seasonal cycle - Albedo feedbacks intentionally omitted
(no snow, ice) - Land points have 10 times lower thermal
inertia than the ocean
Warm Arc�c – Cold Con�nents (‘wet’ con�nents, no albedo feebacks)
‘Reduced’ sea ice – increased heat content before cold season ‘Ghost forcing’ added to Barents and Chukchi seas in summer
Summary/conclusions The Arc�c is warming, sea ice is disappearing North Atlan�c warming and associated increase in the
AW temperature are responsible for mel�ng of a significant por�on of arc�c sea ice
Delayed freeze-‐up, more open water and consequent heat input to the atmosphere lead to significant changes in atmospheric circula�on, including switching the polarity of the transpolar dri� to posi�ve phase.
Significant nega�ve AO/NAO trend in the recent years is a manifesta�on of the warming in the Arc�c Ocean
Negative AO/NAO trends are responsible for the negative winter temperature trends in Northern Eurasia (also in the lower 48)