2. Outline of the talk Why study Arctic Boundary current? Methods Eddy-permitting/resolving simulations Observational evidence Mechanisms of the current Summary and future work

3. Arctic Boundary Current Schematic follows McLaughlin et al. (2009), Rudels et al. (1994), Schauer et al. (2002), Shimada et al. (2005), Steele et al. (2004), Woodgate et al (2007)  Flows along the continental shelf slope  Quickest way to transport water around the Arctic Ocean  Following observations he current transports Atlantic Water and Barents Sea waters through Eurasian and Canadian Arctic; affects Arctic halocline Unknown  Water masses constituting the Arctic Boundary current  Variability and mechanisms of the current  Pathways: does it follow the shelf slope all way around Arctic?  Flows along the continental shelf slope  Quickest way to transport water around the Arctic Ocean  Following observations he current transports Atlantic Water and Barents Sea waters through Eurasian and Canadian Arctic; affects Arctic halocline Unknown  Water masses constituting the Arctic Boundary current  Variability and mechanisms of the current  Pathways: does it follow the shelf slope all way around Arctic?

4. OCCAM Global ~8 km, 66 z-levels Eddy-resolving in the central Arctic and eddy-permitting on the outer shelf and shelf slope Sea ice: EVP + 2-layer Semtner Forcing: NCEP reanalysis fields 1985-2006 Methods: Models NEMO-NOCS (ORCA025) Global, ~6-15 km in the Arctic, 64/75 z-levels Eddy-permitting in the central Arctic, eddy non-permitting elsewhere in the Arctic Sea ice: LIM2 (VP + 2-layer Semtner) Forcing: DFS3 (ECMWF winds) reanalyses fields (1958-2007)

5. Conductivity-Temperature-Density measurements (CTD) NABOS (Nansen and Amundsen Basin Observational System) cross-slope sections summer 2002-2009: Typical station separation 6-20 km; 1-2 km (resolved Rossby radius) in 2007/2009 at 126°E Using shipboard SeaBird (SBE19), vertical resolution 1 m Methods: Observations Current meter measurements Long-term autonomous moorings at NABOS sections Acoustic current meter (ACM) on the McLane Mooring Profiler, vertical resolution 2 m Alaskan Mooring array at 152°W 31°E 126°E 152°W

6. T, S, σ and along-shelf U, Barents Sea Shelf at ~31°E (OCCAM 1989-2006) σ 0, U cm/s S, T°C, σ 0,

7. σ 0, U cm/s S, T°C, σ 0, T, S, σ and along-shelf U in Laptev Sea ~126°E (OCCAM, 1989-2006)

8. S, T°C, σ 0, σ 0, U geost cm/s T, S, σ and along-shelf U, Laptev Sea Shelf at ~123°E, Aug 2007

9. Model cores of the Arctic Boundary Current in Laptev Sea at ~126°E Cores defined with max along-shelf velocity at the section FSB (red) is slower than ASBB (blue) ASBB is fresher (and colder) than FSB Large changes in winter ASBB salinity: shelf waters entrainment Cores defined with max along-shelf velocity at the section FSB (red) is slower than ASBB (blue) ASBB is fresher (and colder) than FSB Large changes in winter ASBB salinity: shelf waters entrainment

10. OCCAM 1989-2006 σ 0, U cm/s Current meter array at ~152°W, 2002- 2003 T, S, σ and along-shelf U, Alaskan Shelf at ~152°W Obs. OCCAM

11. Flow on pseudo-neutral surface 27.7 and Montgomery function, OCCAM 1/12° M-function OCCAM Mar 1989-2006  For the Halocline surface (27.70) Barents Sea is PV source. Cyclonic continuous boundary current (ASBB). Outflow through Canadian Archipelago and Fram Straits.  For the Halocline surface (27.70) Barents Sea is PV source. Cyclonic continuous boundary current (ASBB). Outflow through Canadian Archipelago and Fram Straits.  On PnS PV inflow is defined by the Montgomery function gradient across the inflow boundary (G. Nurser)

12. Flow on pseudo-neutral 27.9 surface and Montgomery function, OCCAM 1/12°  For the Atlantic surface (27.90) Fram Strait is a weak PV source. Cyclonic continuous boundary current (FSB). Outflow through Fram Strait.  For the Atlantic surface (27.90) Fram Strait is a weak PV source. Cyclonic continuous boundary current (FSB). Outflow through Fram Strait. M-function OCCAM Mar 1989-2006

13. Mechanisms to generate ASBB: Ekman pumping and Buoyancy  ASBB (density surface 27.7 ) is driven by the Ekman drift west of Novaya Zemlya (top panel) and by the buoyancy loss in winter (bottom panel) Density gain (top) and Ekman pumping (bottom) along with the potential density surfaces 1989-2006, OCCAM 1/12° Ekman pumping 1989-2006, OCCAM 1/12°

14. Summary The Arctic Boundary current is continuous, consists of: the slow Atlantic core (FSB), deep Barents Sea (BSB) core and fast shelf slope core (ASBB) The ASBB is the fastest current, maximum in winter, transports Barents Sea halocline water The ASBB is driven by potential vorticity inflow through St.Anna Trough. The inflow is due to Ekman convergence and and buoyancy loss in the Barents Sea Questions remained Variability and mechanisms of the FSB (seasonal and interannual) Deep Arctic circulation (BSW)