Lagrangian Aspects of the Surface Circulation and mixing on Wide Arctic
Shelves
Andreas Muenchow
Institute of Marine and Coastal Sciences, Rutgers University
71 Dudley Rd., New Brunswick, NJ 08901-8521, U.S.A.
Tel: 1-732-932-3218
Fax: 1-732-932-8578
andreas@ahab.rutgers.edu
http://marine.rutgers.edu/ac/munchow.html
The Arctic Ocean is presently ice covered not for the cold air temperatures but for its vertical salinity stratification. The fresh water that stratifies this ocean derives from the inflow of riverine waters which subsequently spread and mix over the generally broad and shallow continental shelves. Using recent observational data from in situ platforms, I here discuss kinematic and dynamical aspects of the circulation, mixing, and exchange of buoyant shelf waters in the East Siberian, the Chukchi, and the Mackenzie Shelf Seas.
More specifically, I present direct velocity observations from surface drifters (and vessel-mounted ADCPs) that indicate correlation, terms in the momentum balance, and dispersive characteristics. At mid-latitudes riverine discharges generally force coastally trapped along-shore coastal currents. Often these current in semi-geostrophic balance that facilitates little across-shelf exchange. In contrast, Arctic riverine discharges prior to the onset of winter freezing appear on the shelf as unsteady and diffusive flows susceptible to but not always correlated with wind stress forcing. Drifters cross isobaths easily and exhibit isotropic dispersive characteristics. Dispersion coefficients are about 2-3(107cm2s-1. These characteristics resemble those of open ocean drifters more than they resemble the generally anisotropic dispersive characteristics of drifters released into the coastal ocean.
