The Atlantic Inflow: Origin, Circulation, and Role in Arctic Change

1. The Atlantic Inflow – forcing, advection and variabilityA. ProshutinskyWoods Hole Oceanographic InstitutionDAMOCLES workshop,December 6, 2006Bremen, Germany

2. Questions: • What is the origin of Atlantic waters in the Arctic Ocean and why do they inflow to the Arctic? • How does AW circulate in the Arctic Ocean? • What is the range of AW variability at different time scales? • How does AW influence rate of sea ice melt in the Arctic and what is its role in the Arctic change?

3. 1. Why does Atlantic water penetrate to the Arctic Ocean?Historically this was explained by different scientific schools differently:a) driven by global thermohaline factors externally (positive freshwater balance of the Arctic Ocean)b) driven by Arctic winds which remove surface waters from the Arctic Ocean and Atlantic water inflow compensates this.c) there are also other factors which can influence this basic processes such as bathymetry, stratification, sea ice melt/freeze cycle.

4. Schematic of an estuarine circulation: A freshwater flux R drives an outflow at the surface. Entrainment of water and salt from the deeper layer increases the outflow and drives an inflow to balance the salt budget. In the Arctic Mediterranean the freshwater driven in- and outflows are side by side, not on top of each other.Courtesy of M. Tomczak

24. How to solve these problems? • Numerical experiments? • Volume and salt budget calculations? • Accuracy? What kind of observations is needed???

25. 2. How does Atlantic water circulate in the Arctic Ocean?a) cyclonically/anticyclonicaly and what does drive these regimes?b) what is the ratio of between AW inflow via Fram Strait and via the Barents Sea?c) how do inflows change seasonally, interannualy and from decade to decade?

26. How does AW circulate in the Arctic Ocean?

28. Models with cyclonic circulation of Atlantic water MOM high resolution MOM low resolution POM Global, OPA AOMIP studies showed that some models generate cyclonic circulation which intensity changes in time insignificantly. Other model results show that circulation changes and even may reverse its direction. What is the origin of these reversals? MOM

29. Models with anticyclonic circulation of Atlantic layer Finite elements Several models showed that the Atlantic water circulation is very stable and is anticyclonic!!! Note that model forcing, initial conditions, bathymetry, etc. MOM high resolution were identical in the models reproduced cyclonic and anticyclonic motion of the Atlantic water. Well organized and coordinated observations are needed to solve this question and IARC’s NABOS and CABOS observational programs can address this problem MOM

31. Atlantic Water circulation There are several scientific questions associated with the origin, direction, and variability of the Atlantic water layer circulation in the Arctic Ocean. Observational studies suggest that this circulation is cyclonic and its intensity may change depending on Arctic Oscillation or North Atlantic Oscillation regime. How surface forced ocean regulates circulation in deep layers is not clear. Figures above suggest that deep circulation does not change significantly when surface circulation changes from anticyclonic to cyclonic.

32. Circulation and potential vorticity(courtesy of Jiayan Yang, WHOI) 0.8Sv 0.8Sv 2.0 Sv 2.0 Sv 1.0 Sv 1.0 Sv Realistic bathymetry Depth in Fram Strait is reduced

33. Penetration of The Great Thermal Anomaly - (1990’s) Variability of Atlantic water parameters 98 03 93 94 91 89 By topographically-steered Currents and thermohaline Intrusions

35. Circulation of Atlantic waters at ~300m and change of rotation sense from 3 AOMIP models from top to bottom: LANL, UW, and AWI

36. Left panel: Numerals I–VI indicate temperature sections (°C) taken in 2004 (data are reduced by means taken from the 40-year mean EWG [1997] climatology). Numerals I, III, and IV indicate cross-sections occupied during IB Kapitan Dranitsyn, RV Lance, and FS Polarstern cruises respectively, numerals II and VII refer to sections carried out during SS Akademik Fedorov cruise, numeral V refers to a cross-section from the Russian manned drifting station SP-32, and numeral VI indicates a panel showing vertical profiles of temperature (°C) measured at the North Pole. Horizontal axes show distance in panels I–V and VII and temperature in panel. Right panel shows details of high resolution mooring array locations (left panel is modified after Polyakov, et al. , 2005)

41. Atlantic Water layer structure

42. B A

43. B A

45. 3. What is the role of AW in the arctic warming and sea ice melt? • Role of the Fram Strait AW branch • Role of the Barents Sea AW branch

48. ?

49. The Arctic Mediterranean can be considered as a large fjord supplied in the interior with freshwater from rivers, melting icebergs and precipitation, and which communicates with the North Atlantic. This fresh water mixes with saline ocean water. In steady state two conservation laws apply to such systems: --- the conservation of volume and --- the conservation of salt. This requires a circulation with an outflow larger than the freshwater fluxes and a compensating inflow.

50. Eddy Carmack’s Question: Is there a contiguous (e.g. a daisy chain) of gravity-driven flow that serves to transport freshwater in a clockwise direction around continents and islands in the Northern Hemisphere, and thus connect the Pacific, Arctic and Atlantic?