Different Magnitudes of Projected Subsurface Ocean Warming
SUPPLEMENTARY INFORMATION
Around Greenland and Antarctica
DOI: 10.1038/NGEO1189
Different magnitudes of projected subsurface
ocean warming around Greenland and Antarctica
Supplementary Text
Jianjun Yin1*, Jonathan T. Overpeck1, Stephen M. Griffies2,
Aixue Hu3, Joellen L. Russell1, and Ronald J. Stouffer2
1. Department of Geosciences, University of Arizona
2. Geophysical Fluid Dynamic Laboratory, NOAA
3. National Center for Atmospheric Research
* Corresponding author address:
Dr. Jianjun Yin
Department of Geosciences, University of Arizona
Tucson, AZ 85721
Email: yin@email.arizona.edu; Phone: (520) 626-7453
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1.
Oceanic Heat Transport in the GFDL CM2 Models
The performance of the GFDL CM2 in simulating the climate system has been
systematically evaluated1-4. Various metrics indicate that the GFDL CM2 is among the best
models in many aspects5. The ocean components of CM2.0 and CM2.1 use similar numerical
methods and physical parameterizations. In particular, advective tracer transport and vertical
mixing processes are identical. Both ocean models parameterize subgrid scale eddy processes via
diffusive and advective (or skew diffusive) operators oriented along isopycnal surfaces or neutral
surfaces6,7. The heat flux arising from such neutral physics processes is proportional to
,
(S1)
where the mixing tensor acting on the gradient of the tracer concentration is
.
Here,
is the neutral diffusion coefficient,
is the skew-diffusivity coefficient, and S is the
magnitude of the neutral slope with components
(
(S2)
and
. CM2.0 sets the neutral diffusivity
) equal to the eddy advection diffusivity, whereas CM2.1 sets the diffusivity equal to a
constant 600 m2 s-1. In both models, the skew diffusivity (
averaged horizontal density gradient
2
) is proportional to the vertically
,
where
(S3)
is a dimensionless tuning parameter set to 0.07, L a length scale set to 50 km,
a
buoyancy frequency set to 0.004 s-1, g is the gravitational acceleration equal to 9.8 m s-1,
1035 kg m-3 is the reference density for the Boussinesq approximation, and
is the average
of the horizontal density gradient taken over the depth range from 100 to 2000 m. Equation (1)
gives the vertically integrated heat transport by advection and parameterized neutral physics
processes.
2.
Meltwater Experiments with the NCAR CCSM3 Model
Similar to the GFDL CM2, the NCAR CCSM3 is also a leading fully coupled
atmosphere-ocean general circulation model8. The impact of additional meltwater from polar ice
sheets has been investigated using CCSM39,10. The baseline experiment is the standard SRES
A1B scenario run without additional meltwater from polar ice sheets. In the subsequent
experiments, additional meltwater from the GIS or WAIS is added uniformly in the surrounding
oceans of polar ice sheets. The initial meltwater flux at year 2000 is set to 0.01 Sv and 0.002 Sv
(1 Sv =106 m3/s) for the GIS and WAIS melt experiments, respectively. The meltwater flux
increases by 1% or 3% per year compound until 2099, representing the range of possible ice
sheet melt. The impact of the additional meltwater on the climate and ocean system can be
studied by comparing these meltwater experiments with the baseline experiment (Fig. S9).
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Supplementary Material References
1.
Delworth, T. L. et al. GFDL’s CM2 global coupled climate models. Part I: Formulation
and simulation characteristics. J. Clim. 19, 643-674 (2006).
2.
Gnanadesikan, A. et al. GFDL’s CM2 global coupled climate models. Part II: The
baseline ocean simulation. J. Clim. 19, 675-697 (2006).
3.
Wittenberg, A. T. et al. GFDL’s CM2 global coupled climate models. Part III: Tropical
Pacific climate and ENSO. J. Clim. 19, 698-722 (2006).
4.
Stouffer, R. J. et al. GFDL’s CM2 global coupled climate models. Part IV: Idealized
climate response. J. Clim. 19, 723-740 (2006).
5.
Gleckler, P. J., Taylor, K. E. & Doutriaux, C. Performance metrics for climate models. J.
Geophys. Res. 113, D06104 (2008).
6.
Griffies, S. M. et al. Formulation of an ocean model for global climate simulations.
Ocean Science 1, 45-79 (2005).
7.
Griffies, S. M. The Gent-McWilliams skew flux. J. Phys. Oceanogr. 28, 831-841 (1998).
8.
Collins, W. D. et al. The Community Climate System Model: CCSM3. J. Clim. 19, 21222143 (2006).
9.
Hu, A., Meehl, G. A., Han, W. & Yin, J. Transient response of the MOC and climate to
potential melting of the Greenland Ice Sheet in the 21st century. Geophys. Res. Lett. 36,
L10707 (2009).
10.
Hu, A., Meehl, G. A., Han, W. & Yin, J. Effect of the potential melting of the Greenland
Ice Sheet on the meridional overturning circulation and global climate in the future.
Deep-Sea Res. II, doi:10.1016/j.dsr2.2010.10.069 (2011).
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Table S1. The IPCC Fourth Assessment Report (AR4) models with the simulations and projections of ocean temperature available at
PCMDI. The simulations of the upper ocean temperature (0-1000 m) during 1951-2000 are compared to the observation (ref. 18). The
root-mean-square-error (RMSE) is calculated for each model. The models with RMSE greater than 4 and with problems at high
latitudes (IAP FGOALS) are not used. Totally 19 AR4 models are chosen for the ensemble mean projections of the 21st century. Data
from 13 AR4 models are available for the 22nd century projections.
Model
BCCR BCM2.0
CCCMA CGCM3.1
CCCMA CGCM3.1 T63
CNRM CM3
CSIRO MK3.0
CSIRO MK3.5
GFDL CM2.0
GFDL CM2.1
GISS AOM
GISS EH
GISS ER
IAP FGOALS
INGV ECHAM4
IPSL CM4
MIROC3.2 HIRES
MIROC3.2 MEDRES
MIUB ECHO G
MPI ECHAM5
MRI CGCM2.3.2
NCAR CCSM3
NCAR PCM
UKMO HADCM3
Institution
Bjerknes Centre for Climare Research, Norway
Canadian Centre for Climate Modeling Analysis, Canada
Canadian Centre for Climate Modeling Analysis, Canada
Centre National de Recherches Meteorogiques, France
Commonwealth Scientific and Industrial Research Organisation, Australia
Commonwealth Scientific and Industrial Research Organisation, Australia
Geophysical Fluid Dynamics Laboratory, USA
Geophysical Fluid Dynamics Laboratory, USA
Goddard Institute for Space Studies, USA
Goddard Institute for Space Studies, USA
Goddard Institute for Space Studies, USA
Institute of Atmospheric Physics, China
National Institute of Geophysics and Volcanology, Italy
Institut Pierre Simon Laplace, France
University of Tokyo, Japan
University of Tokyo, Japan
University of Bonn, Meteorological Administration, Germany/Korea
Max Planck Institute for Meteorology, Germany
Meteorological Research Institute, Japan
National Center for Atmospheric Research, USA
National Center for Atmospheric Research, USA
Hadley Centre for Climate Prediction and Research, UK
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Root-Mean-SquareError (oC)
1.70
1.70
1.43
2.21
2.18
1.94
1.83
1.37
4.13
2.12
4.64
1.83
1.99
1.63
1.80
1.57
1.60
2.41
1.69
1.63
2.42
1.47
Figure S1. Global map of recent observed and ensemble mean projections of subsurface (200500 m) ocean warming (oC) for the 21st and 22nd century under the A1B scenario. a, Observed
annual mean ocean temperature18 (shading) and the bias of the ensemble mean simulation by 19
AR4 models during 1951-2000 (contours). b, Projected ocean warming by 19 AR4 models
during 2091-2100. c, Projected ocean warming by 13 AR4 models during 2191-2200. Stippling
in b and c indicates the ensemble mean divided by the ensemble standard deviation is less than 1,
identifying regions where the models show less agreement.
Figure S2. Individual model projections of the ocean warming (oC) in 200-500 m surrounding
Greenland during 2091-2100. The results are from the A1B scenario runs. See Table S1 for
model information.
Figure S2. (Continued) Individual model projections of the subsurface ocean warming (oC) in
200-500 m surrounding Greenland during 2091-2100.
Figure S3. Changes in total surface heat flux (W/m2) over the 21st century. Upper panels: surface
heat flux during 1991-2000; lower panels: surface heat flux anomalies during 2091-2100.
Positive values indicate downward heat fluxes. Vectors indicate ocean currents (m/s) in 200-500
m.
Figure S4. Ocean temperature changes (oC) over the 21st century. Upper Panels: 73oN; middle
panels: 63oN; lower panels: zonal mean in the Southern Ocean. Contours show the ocean
temperature during 1991-2000. Shading shows the temperature anomalies during 2091-2100.
Figure S5. Changes in volume transport by ocean currents over the 21st century. The time series
include the East Greenland Current (EGC), West Greenland Current (WGC), Atlantic Meridional
Overturning Circulation (AMOC), Southern Ocean Meridional Overturning (SOMOC), North
Atlantic Subpolar Gyre (NA SPG) and Antarctic Circumpolar Current (ACC). The EGC and
WGC are the transport in the upper 500 m across Fram and Davis Strait, respectively. The
indices for the AMOC and SOMOC are, respectively, defined as the maximum overturning
streamfunction at 45oN in the Atlantic and south of 30 oS. The ACC index is the transport across
the Drake Passage. The SPG index is the extrema of the barotropic streamfunction in the gyre
circulation regions compared to a fixed point at the gyre edge.
Figure S6. Sea ice change over the 21st century. Shading shows the annual mean sea ice
thickness anomalies (m) during 2091-2100 compared to 1991-2000. Black and red lines indicate
the annual mean sea ice extent (ice concentration greater than 15%) during 1991-2000 and 20912100, respectively.
Figure S7. Wind Stress anomalies in the CM2.0 and CM2.1 projections. Upper and middle
panels: solid lines show wind stress and dashed lines show the anomalies. Bottom panels: zonal
mean of heat transport (TW) by advection in CM2.1. Vectors show heat transport and contours
are isopycnic surfaces (σo). Black and red colors indicate the results during 1991-2000 and 20912100, respectively. Box indicates the region of the enhanced upwelling of cold deep waters.
Figure S8. Barotropic streamfumction (Sv) in the Southern Ocean. Black color shows the values
during 1991-2000. Red color shows the values during 2091-2100.
Figure S9. Feedback of meltwater on subsurface ocean warming. The simulations are performed
using the NCAR CCSM3 climate model. The results show the ocean temperature anomalies
induced by additional meltwater in the A1B scenario run. Upper panel: 1% increase rate in
Greenland melt; middle panel: 3% increase rate of Greenland melt; lower panel: 3% increase rate
of Antarctic melt. The additional meltwater only has a very small impact (±0.1 oC) on the
subsurface warming around Greenland and Antarctica. See ref. 28 for details.