Arctic Sea Ice, Atlantic Water Transport in the Arctic and Adjacent Seas, and NAO

1. Jinlun Zhang Polar Science Center Arctic Sea Ice, Atlantic Water Transport in the Arctic and Adjacent Seas, and NAO Jinlun Zhang PSC/APL/UW

2. Coworkers: Drew Rothrock Mike Steele Ron Lindsay Axel Schweiger http://psc.apl.washington.edu/IDAO/ for data sets, movies of sea ice thickness

3. Outline • Motivation • Model description • AW transport in the Arctic & adjacent seas • Variability and decline of arctic sea ice • Link between AW transport and sea ice • Link between AW transport and NAO • Conclusions

4. Motivation • Satellite and submarine observations and model results show a rapid decline of arctic sea ice in recent years. • The decline is linked to changes in the atmospheric circulation (NAO/AO). • Changes in atmospheric circulation also responsible for increased presence of Atlantic water (AW) in the Arctic. • How is the northward AW transport varying on interannual and decadal time scales in the Arctic and adjacent seas? • What is the role of AW in the variability and decline of arctic/NH sea ice? • Need a coupled global ocean and sea ice model to examine the link between AW transport and NH sea ice.

5. A global Parallel Ocean and sea Ice Model (POIM) • POP ocean model. • Multicategory thickness and enthalpy distribution (TED) sea-ice model. • Parallel LSR (line successive relaxation) ice dynamics solver. • Generalized curvilinear coordinate system. • NCEP Reanalysis forcing 1948−2003.

6. Ocean velocity at 15 m (1948−2003 mean) One vector is drawn for every 4 grid cells

8. 1948−2003 mean AW inflow: 1.1 Sv Greenland Spitzbergen 1948-2003 mean ocean velocity across Fram Strait, cm/s 1948−2003mean AW inflow: 1.1 Sv Spitzbergen Norway 1948-2003 mean ocean velocity across Barents Sea Opening, contour interval 0.5 cm/s

9. Interannual variability of NH sea ice volume Annual September

10. Satellite passive microwave images of minimum ice concentration and modeled September ice concentration and thickness 1979 2003 Observations and model results show a substantial reduction in summer ice concentration and thickness in 2003.

11. Interannual variability of northward AW transport (Sv) Iceland-Scotland Ridge Correlation with NAO: 0.49 Fram Strait * 1 year lag Correlation with NAO: 0.43* Barents Sea Opening Correlation with NAO: 0.52 • Increasing AW transports • Especially since 1960s • Close correlation with NAO • Trends linked to NAO elevation NAO

12. 0.57 0.55 0.51* * 1 year lag 0.53

14. Lagged correlations: ISR heat influx ~ LaggedNH sea ice volume ISR heat influx ~ Lagged upward ocean heat flux in the Arctic Delayed effect of AW transport on sea ice Delayed effect of NAO on sea ice

15. Modeled ice thickness and satellite observed ice edge, Septembers

16. Conclusions • Northward AW transport is increasing in the Arctic and adjacent seas, bringing more heat to the polar ocean, since 1960s. • The variability of AW volume and heat fluxes is closely correlated with NAO; the positive trend is closely linked to the recent NAO elevation. • Upward oceanic heat flux used to melt ice in the Arctic Ocean is increasing and is linked to increasing heat transport from the North Atlantic Ocean. • Increasing heat transport from the North Atlantic Ocean is accelerating sea ice melting. • AW heat transport impacts arctic sea ice 2−3 years later, representing a delayed effect of NAO on sea ice. • If AW heat influx continues to increase, and the NAO does not shift to an enduring negative mode, the decline of arctic sea ice is likely to continue.

17. Thanks

18. Grid configuration of the global POIM Fram Strait Barents Sea Opening Iceland-Scotland Ridge (ISR)

19. Comparison of submarine and model ice draft W: winter S: summer

20. Upward ocean heat flux is used to actually melt ice