1. Changsheng Chen 1, Guoping Gao 1, Andrey Proshuntinsky 2 and Robert C. Beardsley 2 1 Department of Fisheries Oceanography University of Massachusetts-Dartmouth (UMASSD), New Bedford, MA 02744 2 Department of Physical Oceanography Woods Hole Oceanographic Institution, Woods Hole, MA 02543 Website: http://fvcom.smast.umassd.edu E-mail: c1chen@umassd.edu; ggao@umassd.edu; aproshuntinsky@whoi.edu; rbeardsley@whoi.edu An Unstructured Grid Arctic Ocean Model (FVCOM-Arctic): Validations via Observations and Needs for Horizontal Resolution

2. Outline A brief description of the FVCOM-Arctic system; Comparison between high- and coarse resolution FVCOM- Arctic results; Comparison with the observations, with focus on water currents.

3. Coarse-grid AO-FVCOM/UG-CICE (10 km to 50 km) Generalized Ecosystem Model (FVCOM-GEM) Global Ocean FVCOM (Coupled with Sea Ice Model: UG-CICE) (5 km to 50 km) Forcings FVCOM System KEY Data assimilation Larval data High-resolution AO-FVCOM/UG-CICE (1 km to 50 km) Astronomic tides (8 major constituents) Arctic Ocean FVCOM System (AO-FVCOM) Offline Models River discharges (Number: 406 ) Winds, Heat flux, P-E, Sea Level Pressure (ECMWF-ERA-15) Satellite SST Survey T,S Boundary (B) nesting (common B) Forcings Same Initial C Multi-Stage Zooplankton Model (IBM and Concentration-based) Nutrients, Chl-a

5. Coarse grid (10-50 km)Finer grid (1.0-25 km)

6. Procedures used in the experiment Spin up the FVCOM-Global for 50 years with inclusion of the data assimilation of water temperature and salinity on a monthly base. Forcing: daily meteorological forcing (ECMWF-ERA-15), river discharges, and tides. Initialize AO-FVCOM with FVCOM-Global fields and run AO-FVCOM through a mass conservative nesting boundary provided by FVCOM-Global. This applies for both high-and coarse resolution cases.

7. How could we resolve a multi-scale process in the ocean covering the global to regional Arctic Ocean using a model? Multi-Models’ Nesting Mass conversation? Surface wave propagation-energy accumulation?

8. Common boundary Non-hydrostatic process Unstructured nesting approach: Mass conservation

11. Monthly averaged currents at 400 m (summer) Coarse grid

12. Monthly averaged currents at 400 m (summer) Finer grid

14. Bering Strait, Chukchi Sea and Alaska coast Coarse grid Finer grid Annual mean vertically averaged currents in the depths of 0-50 m Transports across Bering Strait: 0.8 Sv for the coarse grid case 1.1 Sv for the finer grid case

15. Canadian Archipelago Annual mean vertically averaged currents in the depths of 0-50 m Coarse grid Finer grid

16. Parry Channel in Canadian Archipelago Annual mean velocity at a depth of 400 m Coarse grid Finer grid

17. Coarse gridFiner grid Annually averaged currents at a depth of 1500 m

18. Annually averaged near-surface currents Coarse gridFiner grid

19. Annually averaged currents at a depth of 700 m Finer grid AO- FVCOM results Red: modeled Black: observed

20. Summary AO-FVCOM provides a new model tool for the study of the Arctic Ocean. By resolving the complex coastal geometry and steep bottom topography, FVCOM is robust to capture the complex structures of water currents in the Arctic Ocean and adjacent regions An attention is needed for the horizontal resolution of the model in order to capture the cross-shelf scale and intensity of the currents over the slope and in the regions characterized with complex geometries.