1. Numerical modeling of the circulation and sea ice in the Canadian Arctic
John (Qiang) Wang, Paul G. Myers,
Xianmin Hu, Andrew B.G. Bush
Dept. of Earth and Atmospheric Sciences, University of Alberta

2. Outline 1. Model configuration
2. Model validation: Downwelling shortwave radiation
3. Model results: Southward flow in M’Clintock Channel
4. Summary

3. Model Domain Arctic Ocean Beaufort Sea Canadian Arctic Archipelago
This figure show the model domain and water depth. The water is deep in Arctic Ocean and central Baffin Bay.
NEMO model is used, ice model use LIM2, Elastic Viscous Plastic ice rheology is used in ice model.
We use tripolar grid, the model resolution is about 7.5 km in Lancaster Sound.
The background is the bathymetry.
There are many shallow sills and narrow straits in Canadian Arctic.
There are three major channels connecting the Arctic Ocean to Baffin Bay, they are Nares Strait, Jones Sound, and Lancaster Sound.
The water flow from Arctic Ocean to Baffin Bay through those three channels .
Canadian Arctic Archipelago
Baffin Bay
Model: NEMO LIM2-EVP ice rheology, Bathymetry: IBCAO
Tripolar Grid: resolution km, 7.5 km in Lancaster Sound, 46 levels

4. Model boundary condition
T S U V
Ice BC data
PIOMAS, UW
Z.Wang BIO
Q10, U10 V10
LW & SW Radiation
Precipitation and snow
CORE
T,S PHC
Surface air temperature is revised based on IABP/POLES data
The forcing data is from CORE data.
The ocean boundary data are derived from a 1 degree global model.
The ice boundary data are derived from a Pan-Arctic Model.
The surface air temperature is from CORE data but is revised based on IABP/POLES data.
The initial temperature and salinity are from PHC data.
PIOMAS: Pan-Arctic Ice-Ocean Modeling and Assimilation System.
IABP/POLES: International Arctic Buoy Programme/ Polar Exchange at the sea surface.
CORE: Common Ocean-ice Reference Experiments.

5. Schematic experiments
Start from Sep. 1, and run 5 years and 4 months
Normal year forcing
Inter-annual year forcing
From Jan to Nov
We also set the ice velocity is zero in Nares Strait from mid-Feb to mid-July. The date when the ice velocity is zero is according to Kwok et al
Because the model could not simulate well about the ice bridge in Nares Straits.

6. Downwelling shortwave radiation
Arctic Global Radiation data in June
Location of the data
The top left figure show the downwelling shortwave radiation from Arctic Global Radiation dataset in June.
The Arctic Global radiation dataset is based on observation.
The bottom left figure show the downwelling shortwave radiation from core data,
Both dataset show that the downwelling shortwave radiation is high on Greenland.
There is difference between AGR data and CORE data in nothern Baffin Bay.
The right figure show the location of AGR data.
Arctic Global Radiation dataset lack of observational data in Baffin Sea.
From Serreze et al. (1998)
Arctic Global Radiation (AGR) data set is from NSIDC (Box et al.,1998).
AGR data is based on observation.
CORE data in June

7. Downwelling Shortwave radiation: AGR – CORE data
May
June
The four figures show the difference between AGR downwelling shortwave radiation data and CORE data, that is AGR data minus CORE data
There are about 60 Wm-2 difference in May and June in northern Baffin Bay. Downwelling shortwave radiation in Arctic Global Radiation dataset is higher.
CORE data is low in northern Baffin Bay.
In July and August, the difference between reduced to about 30 Wm-2 in northern Baffin Bay.
In Arctic Ocean near the Canadian Arctic, observational data is higher than CORE data in May but is smaller than CORE data in July.
July
August
Arctic Global Radiation (AGR) data set is from NSIDC (Box et al.,1998)

8. Sea ice concentration 1998 July Observational data (from SSM/I)
(top-right) Model results of sea ice concentration in July 1998 with shortwave radiation correction
The top left figure shows the observational sea ice concentration in July The observational data is from SSM/I.
The top right figure shows the model results of sea ice concentration in July 1998.
The bottom left figure shows the model results of sea ice concentration in July 1998 without shortwave radiation correction.
With shortwave correction, the sea ice concentration agrees well with observation in northern Baffin Bay.
Without shortwave correction, model results of sea ice concentration is higher than observational results.
The sea ice concentration from two experiments is similar in Beaufort Sea.
(left) Model results of sea ice concentration in July 1998 without shortwave radiation correction in normal year and interannual year

9. Sea ice concentration 1999 Obs July 2000 obs July
The top figures show the observational sea ice concentration in July 1999 and 2000.
The bottom figures show the model results of sea ice concentration in July 1999 and 2000.
The model results show there is Polynya in southern Beaufort Sea, which agree well with observation.
The model results agree well with observational results in Baffin Bay.
1999 Model July Model July

10. Transport through Lancaster Sound
This top figure shows the time series of volume transport through western Lancaster Sound.
The red line show the observational results. The blue line show the model results.
The dot points show the mean value of volume transport.
We calculate the correlation between volume transport from observational results and model results from Jan to Nov
The correlation is 0.53.
But the amplitude of variation from observation is higher than that of model results.
The bottom figure show the freshwater transport through the Lancaster Sound.
The red line is observational results. The blue line is model results.
The correlation between the observational freshwater flux and modeled freshwater flux is 0.54.
The dotted lines are the mean value of freshwater transport.
Observational data is from Dr. Prinsenberg.

11. Currents Byam Martin Channel Western Lancaster Sound
Average currents over top 300m
M’Clure Strait
Parry Channel
This figure shows the mean currents over top 300 m currents in last year model run under normal forcing. One fifth of the horizontal grid point is shown.
The water flows southward through Byam Martin Channel.
The water flows southeastward through M’Clure Strait.
The water flows southward through M’Clintock Channel and then flows northward through Peel Sound.
M’Clintock Channel
Peel Sound

12. Currents Byam Martin Channel Average currents over top 300m
Parry Channel
This figure shows the mean currents over 300m in the last year of model run under normal forcing. This is the zoom in currents.
The water flows southward through Byam Martin Channel and then flows eastward in Parry Channel.
The water flows through M’Clintock Channel is not from Byam Martin Channel but is from M’Clure Strait. In fact, most of the water flows this way.
The water flows northward through Peel Sound and then flows eastward in Parry Channel.
Average currents over top 300m
M’Clintock Channel
Peel Sound

13. Model results
Average meridional stress on the ocean from Dec. to May when the sea ice could not move there
Average currents over top 300m
1. The left figure shows the mean currents over top 300 m in the last year of the model run under normal forcing,
The right figure shows the mean meridional stress on the ocean from Dec. to May when the ice could not move.
In March, the ice could not move in M’Clintock Channel and Peel Sound as strong internal ice stress.
The stress on the ocean is determined by the difference between water velocity and ice velocity,
Since the water flows southward and the ice could not move, the stress on the ocean is northward in M’Clintock Channel,
In Peel Sound, water flow northward while the ice could not move, the stress on the ocean is southward,
Therefore, the stress on the ocean is opposite to the flow direction and it is not the reason that the water flow southward in M’Clintock Channel.
M’Clintock Channel
Peel Sound

14. Model results Real bathymetry Idealized bathymetry
Barrow Strait
Idealized bathymetry
The left figure show the real bathymetry in Canadian Arctic.
There is a sill in Barrow Strait and the water depth is smaller than 150m.
The water depth decreases when the water flows toward Barrow Strait.
The water depth increases when water flows toward the Baffin Bay in Lancaster Sound,
The water depth at the northern entrance M’Clintock Channel is deeper than 200m.
We did a sensitivity experiment to water depth, the water depth is 300m in central Canadian Arctic.
And now there is no sill in Barrow Strait, but there are sills in other straits.
The table shows the mean volume transport through different straits in the first year model run under real bathymetry and idealized bathymetry.
The volume transport through M’Clure Strait increase from 0.31 to 0.90 because the water depth in central Canadian Arctic increases.
The volume transport through M’Clintock Channel and Peel Sound decrease from 0.29 to Therefore, the bottom topography has strong impact on the circulation in the central Canadian Arctic.
Mean volume transport through different straits in the first year run
Byam Martin Channel
M’Clintock
Channel
Peel
Sound
M’Clure
Strait
Lancaster Sound
Real bathy
0.21
-0.29
0.29
0.31
0.73
Idea bathy
0.04
-0.10
0.10
0.90
1.06

15. Potential vorticity
Model results of average Ertel potential vorticity over top 300 m under real topography
Units: kg∙m-4∙s-1×10-7
Model results of average Ertel potential vorticity in the last month under idealized bathymetry
This top figure show the contours of average potential vorticity over top 300 m and the bottom figure show the potentail vorticity under idealized bathymetry.
The potential vorticity in M’Clintock Channel is about same as the potential vorticicy at the upstream.
The water flow southward through M’Clintock Channel because of conservation of potential vorticity.
The potential vorticity is similar in the Parry Channel under idealized bathymetry.
The water flow eastward through Parry Channel because of conservation of potential vortiicty under idealized bathymetry.

16. Impact on sea ice
Mean sea ice concentration from 1984 to 2004 (SSM/I) in September
The figure shows the observational sea ice concentration in central Canadian Arctic from 1984 to 2004 in September.
Because the water flow southward in M’Clintock Channel, the ice also move southward in M’Clintock Channel in summer.
The sea ice concentration is higher in M’Clintock Channel than that in Peel Sound.
In M’Clintock Channel and Peel Sound, the average wind in September is southeastward in September.
The sea ice concentration is relatively low in Peel Sound than M’Clintock Channel.

17. Summary
1. The downwelling shortwave radiation from Arctic Global Radiation dataset in northern Baffin Bay is higher than CORE data from May to August. The model results of sea ice concentration become better after making correction to the CORE data.
Because of topographic steering and conservation of potential vorticity, the water flows southward in M’Clintock Channel and flows northward in Peel Sound, rather than just directly down the sea level gradient from the Beaufort Sea to Lancaster Sound and beyond.

18. Nares Strait Nares strait closed for sea ice from mid-Feb to mid-July
Nares Strait open