HR: 0800h
AN: C41A-0179    [Abstracts]
TI: The West Greenland and Ellesmere Coastal Currents: Spatial Scales of Freshwater Fluxes in Nares Strait From Synoptic Velocity Observations
AU: Brown, L M
EM: lbrown@udel.edu
AF: Graduate College of Marine Studies, University of Delaware, Robinson Hall, Newark, DE 19716 United States
AU: * Muenchow, A
EM: muenchow@udel.edu
AF: Graduate College of Marine Studies, University of Delaware, Robinson Hall, Newark, DE 19716 United States
AB: The Canadian Archipelago constitutes one major pathway of freshwater from the Arctic Ocean into the North-Atlantic. The hypothesized freshwater flux is hypothesized to impact vertical stratification in the ocean and thus the global thermohaline circulation. While this simplification appears reasonable, it involves a number of physical processes all of which are poorly understood in general and most are ignored in the Arctic System Science context that requires integrations over large spatial and temporal domains. What are the physics that transform 0.0 psu salinity (fresh) water at the land-ocean, land-ice, or ice-ocean interfaces to the so-called "fresh" 34.9 psu salinity water at 2000-m depth in the Labrador Sea? How do fresh and thus buoyant waters mix vertically from the surface down and how do they advect horizontally from shallow coastal areas to the deep ocean? These are non-trivial dynamical questions that require appreciation of geophysical fluid dynamics. More specifically, the earth's rotation imposes a very strong dynamical constraint that often prevents across-shelf exchange. It's dynamically hard to move buoyant material from coastal waters to the deep ocean. It also explains why most fresh water is generally found adjacent to coastal regions. Buoyant discharge from point sources (.e.g., a river or the Arctic ocean) or line sources (the ice edge, the melting ice sheet of Greenland) cause circulation that vary at the internal Rossby radius of deformation. This fundamental dynamical scale is generally less than 10-km in most high-latitude ocean systems. Besides buoyant discharges, plumes, and coastal currents, it also scales eddies throughout the ocean. We here provide first examples on the spatial scales of the three-dimensional velocity field in Nares Strait and northern Baffin Island. Our 2003 surveys off western Greenland and Ellesmere Islands using data from the acoustic Doppler current profiler system aboard the USCGC Healy reveal complex but dynamically consistent flow patters that indeed suggest the internal deformation radius of about 5-km as the dominant spatial scale of variability. We find coastally trapped flows both off Ellesmere Island where they advect fresh waters southward and coastally trapped flows off Greenland where they advect fresh waters northward. Spatially variable tidal currents constitute a major source of temporal variability and we predict them using both state-of-the-art numerical models as well as a locally adapted least-squares function fitting. The two methods agree surprisingly well and give us great confidence in both model and data. It also gives confidence that the observed coastally trapped flows represent a significant signal. Biogeochemically motivated studies usually do not resolve the scales of these features in time or space resulting in severely aliased fields.
UR: http://newark.cms.udel.edu/~muenchow/0307adcp
DE: 4207 Arctic and Antarctic oceanography
DE: 4508 Coriolis effects
DE: 4512 Currents
DE: 4528 Fronts and jets
DE: 4594 Instruments and techniques
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting