Variability of Arctic sea ice

143 Pages·2010·25.57 MB·English

Variability of Arctic sea ice
Nikolay Vladimirovich Koldunov
79
Berichte zur Erdsystemforschung
2010

Reports on Earth System Science

79
Berichte zur Erdsystemforschung
2010
Variability of Arctic sea ice
Nikolay Vladimirovich Koldunov
aus Sankt Petersburg, Russland
Hamburg 2010
79
Reports on Earth System Science
2010
ISSN 1614-1199
Nikolay Vladimirovich Koldunov
Max-Planck-Institut für Meteorologie
Bundesstrasse 53
20146 Hamburg
Germany
Als Dissertation angenommen
vom Department Geowissenschaften der Universität Hamburg
auf Grund der Gutachten von
Prof. Dr. Detlef Stammer
und
Prof. Dr. Jochem Marotzke
Hamburg, den 23. April 2010
Prof. Dr. Jürgen Oßenbrügge
Leiter des Departments für Geowissenschaften
ISSN 1614-1199
Variability of Arctic sea ice
Nikolay Vladimirovich Koldunov
Hamburg 2010
Cover picture
Upper panel: Mean sea ice concentration analyzed from the GSFC satellite data
over the period 1980-1999 for (left) March and (right) September. Lower panel:
Standard deviation of monthly mean sea ice concentrations analyzed from the
GSFC satellite data over the period 1980-1999 for (left) March and (right)
September. Rectangles indicate geographic locations for which time series of sea
ice concentrations are shown in Fig. 2.9
i
Contents
Dedication xi
Acknowledgement xiii
Abstract 1
1 Introduction 3
1.1 Goals of the thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2 Present-day Arctic Sea Ice Variability in the Coupled
ECHAM5/MPI-OM Model 9
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2.1 MPI-OM model . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2.2 Satellite observations . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.3 In situ data . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3 Sea ice concentration and thickness . . . . . . . . . . . . . . . . . . . 17
2.3.1 Seasonal distribution of sea ice concentration . . . . . . . . . 17
2.3.2 Seasonal sea ice thickness . . . . . . . . . . . . . . . . . . . . 21
2.3.3 Interannual variations of sea ice concentration . . . . . . . . . 24
2.4 Sea ice transports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2.5 Forcing fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.5.1 Atmospheric forcing . . . . . . . . . . . . . . . . . . . . . . . 30
2.5.2 Ocean forcing . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.6 Discussion and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . 37
3 Adjoint-based sensitivities of the Arctic sea ice 41
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.2 Present knowlege . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.3 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.3.1 MITgcm model setup . . . . . . . . . . . . . . . . . . . . . . 47
3.3.2 Adjoint calculation of sensitivities . . . . . . . . . . . . . . . 49
3.3.3 Experimental design . . . . . . . . . . . . . . . . . . . . . . . 50
3.4 Comparison of satellite and simulated SIC . . . . . . . . . . . . . . . 52
ii Contents
3.5 Spatial variability of mean adjoint sensitivities . . . . . . . . . . . . 58
3.6 Adjoint sensitivities during the three time periods: 1980-1989, 1990-
1999, and 2000-2007 . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.7 Time evolution of sensitivities in different regions . . . . . . . . . . . 86
3.8 Five-year run . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
3.9 Discussion and conclusions . . . . . . . . . . . . . . . . . . . . . . . . 98
4 Conclusions and outlook 105
4.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
4.2 Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Bibliography 111
iii
List of Figures
1.1 Arctic Ocean including geographical place names. The Amerasian
Basin,mentioned inthetext, includestheregion fromtheLomonosov
RidgetowardsthePacificOcean. TheEurasianBasinincludesregions
from the Lomonosov Ridge towards the Atlantic Ocean. Based on a
map produced by the International Bathymetric Chart of the Arctic
Ocean (IBCAO), Jakobsson et al. (2008). . . . . . . . . . . . . . . . 4
2.1 Upper panel: Mean sea ice concentration analyzed from the GSFC
satellite data over the period 1980-1999 for (left) March and (right)
September. Lowerpanel: Standarddeviationofmonthlymeanseaice
concentrations analyzed fromthe GSFC satellite data over the period
1980-1999for(left)Marchand(right)September. Rectanglesindicate
geographiclocationsforwhichtimeseriesofseaiceconcentrations are
shown in Fig. 2.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2 Upper panel: March mean sea ice concentrations (1980-1999) simu-
lated by (left) the ECHAM run and (right) the FNCEP run. Lower
panel: Differences in March mean (1980-1999) sea ice concentrations
of (left) ECHAM minus GSFC and (right) FNCEP minus GSFC. . 18
2.3 Upperpanel: Septembermeanseaiceconcentrations(1980-1999)sim-
ulated by (left) the ECHAM run and (right) the FNCEP run. Lower
panel: Differences in September mean (1980-1999) sea ice concentra-
tions of (left) ECHAM minus GSFC and (right) FNCEP minus GSFC. 19
2 6
2.4 Top panel: September Arctic Sea ice extent (in km 10 ) as observed
over the last 30 years (through 2008; green curve) and as simulated
by the MPI-OM ECHAM run (red curve) and the FNCEP run (blue
curve). Theperiodusedinthisanalysismarkedbyrectangle. Bottom
panel: DistributionofNorthernHemisphereseaiceconcentration(bin
width 0.1 frac., beginning at 0.01 frac.) for September (1980-1999),
as simulated by the two model runs and as observed by satellites. . 20
2.5 Left: ClimatologicalAprilmeanthicknessofobservedseaice,adapted
from Romanov (1995). Right column: mean April sea ice thickness
for (top) ECHAM and (bottom) FNCEP. . . . . . . . . . . . . . . . 21
2.6 Left: Climatological August-September mean thickness of observed
sea ice, adapted from Romanov (1995). Right column: mean August-
September sea ice thickness for (top) ECHAM and (bottom) FNCEP. 22
iv List of Figures
2.7 Distribution of sea ice thickness (bin width 0.5 m, beginning at 0.01
m) as simulated by the ECHAM and FNCEP model runs. . . . . . 24
2.8 Standard deviation of monthly mean sea ice concentrations for
September (1980-1999) (left) in the ECHAM run and (right) in the
FNCEP run. Rectangles indicate geographic locations for which time
series of sea ice concentrations are shown in Fig. 2.9. . . . . . . . . 25
2.9 Time series of mean September sea ice concentrations from different
areas for the period 1980-1999. Shown are GSFC observations (green
curve),theECHAMrun(redcurve)andtheFNCEPrun(bluecurve).
Shown in the top, center and bottom panels are time series from
positions 1 through 3 in Figs. 2.1 and 2.8, respectively. . . . . . . . 26
2.10 Ice motion vectors for March (left column) and October (right col-
umn) for (upper panel) Pathfinder project data, (middle panel) the
ECHAM run, and (lower panel) the FNCEP run. For Pathfinder
data, every fifth vector is shown, for ECHAM and FNCEP runs, ev-
ery second vector is shown. Color-coded is the speed of each vector
−1
(in cm s ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.11 Distribution of seaice velocities fromtheentire NorthernHemisphere
for March (upper panel) and September (lower panel). Percentage
values of the y-axis correspond to histogram bins along the x-axis
−1 −1
with a bin width of 0.01 m s beginning at 0.001 m s . Shown
are Pathfinder data, the ECHAM run and the FNCEP run as green,
red and blue curves, respectively. Note the different vertical scale on
graphs.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.12 Seaicevolume transportthroughtheFram Straitas simulated by the
ECHAM and FNCEP model runs and analyzed by previous studies. 29
2.13 Climatological monthly mean surface air temperature (color coded in
◦
C) and sea level pressure (contours as hPa) fields for (left) March
and (right) September. Shown are results for (upper row) ECHAM
and (lower row) the NCEP-RA1 reanalysis. . . . . . . . . . . . . . . 31
2.14 Toprow: Shownascontoursaredifferencesbetweentheclimatological
monthly mean (left) March and (right) September ECHAM - NCEP-
RA1 SLP (contour interval is 1 hPa). Superimposed as vector field
aretherespectiveclimatological monthlymeandifferencefieldsforice
motions,withonlyeverysecondvectorplottedandspeedscolorcoded
−1
in cm s . Bottom row: Shown as contour lines are differences in
climatological (left) March and (right) September ECHAM - NCEP-
RA1 SAT fields. Superimposed as color are respective ECHAM -
GSFC SIC difference fields. . . . . . . . . . . . . . . . . . . . . . . . 32
2.15 Upper row: Vertical profiles of September ocean; top:temperature,
middle:salinity and bottom:density from PHC climatolofy and model
runs (1980-1999). Green -PHC, red - ECHAM run, blue - FNCEP
run. Parameters are averaged over the area showed at the middle
panel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35