Mid- and High-Latitude Oceanogaphy

SS1.01: Shelf-Basin Interactions in the Western Arctic
Organizer: Terry E. Whitledge, University of Alaska Fairbanks (terry@ims.uaf.edu) ) and Jackie Grebmeier, University of Tennessee (jgrebmei@utk.edu)

This special session would be focused on the processes crucial to understanding the exchange and interaction between Arctic shelves and the basin. This focus encompasses the critical zone comprised of the shelf, shelf break and slope regions where many important biological, chemical, and physical processes undergo significant changes and modifications. The exchange between the shelves and basin in the Arctic is a key element in determining the current extent of global change and the prediction of further change in the future. The focus of the shelf-basin zone targets the area in the Arctic seas where the least is known about transport processes and fluxes, biological activity, chemical modifications, and the paleo-sedimentary environment. The session would emphasize interdisciplinary research and recent process/survey/mooring studies. International participants would be encouraged to submit contributions.

SS1.02: Oceanography and Ecology of the Aleutian Archipelago
Organizers: George L. Hunt, Jr., University of California, Irvine (glhunt@uci.edu) and Carol Ladd, NOAA Pacific Marine Environmental Laboratory (carol.ladd@noaa.gov)

This special symposium will address the oceanography and ecology of the Aleutian Archipelago. This region is relatively poorly known, but is important as the gateway through which nutrients and heat pass from the North Pacific Ocean to the Bering Sea. The region is also important in its own right, as the site of fisheries for Pacific cod and Atka mackerel, and for its populations of marine birds and mammals. During 2001 and 2002, there were two expeditions that investigated the oceanography of the eastern and central Aleutian Islands, with studies of physical oceanography, nutrients and production, zooplankton and marine birds and mammals. In addition, there have been a number of studies of the paleo-ecology of the region based on the remains in middens of the bones of fish, marine mammals and seabirds. Both in paleo records and in the recent work, there is evidence if a gradient in primary production from east to west. There is also a sharp break in the physical system at Samalga Pass (temperature, salinity and nutrients), the last pass through which Alaska Coastal water passes. At this same pass, there are remarkably sharp changes in zooplankton species composition, fish species composition and in the types of marine birds and mammals that are dominant. Thus there appears to be a clear linkage from physics, to nutrients, to production and ecosystem structure. This present-day spatial structuring of the system is echoed in the paleo-record. We will explore the ties of these patterns and processes to atmospheric forcing and the mechanisms whereby shifts in climate could alter the functioning of this system, perhaps differentially in the eastern and western Aleutians. This session will cover a very broad range of topics from regional climatology through physics, nutrients, production, zooplankton, fish, birds and mammals, and human uses, at least in an archeological sense.

SS1.03: Differential Mixing of Salinity and Temperature
Organizer: Dave Hebert, University of Rhode Island (david.hebert@uri.edu) and Chris Rehmann, University of Illinois (rehmann@ux1.cso.uiuc.edu)

The flux of heat and salt by small-scale mixing processes in the ocean are often represented by eddy diffusivity coefficients, generally assumed to be the same for heat and salt. Differential diffusion is the preferential transfer of one of these tracers to the other. The most commonly known differential mixing is double-diffusion (e.g., salt-fingers and double-diffusive convection). A growing body of evidence from laboratory and numerical experiments, and from field observations, has caused this phenomenon to be considered as a serious possibility for turbulent mixing in the ocean. Recent studies have concluded that differential diffusion can cause thermohaline intrusions to form in frontal waters initially stable to double-diffusion, and could even affect thermohaline circulation on the larger scale (A.E. Gargett, 2003, Differential diffusion: an oceanographic primer, Progress in Oceanography 56 (2003) 559-570). The purpose of this special session is to review recently published findings on differential mixing, and provide a forum for new, unpublished laboratory, numerical, theoretical, and observational studies that pertain to differential diffusion.

SS1.04: Integration of Meso/Sub-Mesoscale Hydrodynamics and Acoustic Propagation in Continental Shelf-Break Regions
Organizers: Pat C. Gallacher, Naval Research Laboratory (gallacher@nrlssc.navy.mil) and Steven Finette, Naval Research Laboratory (finette@wave.nrl.navy.mil)

Sub-mesoscale oceanographic phenomena in continental shelf-slope environments can be associated with complex space-time distributions of temperature and salinity. These distributions have a significant effect on both acoustic propagation and acoustic system performance. In addition, mesoscale phenomena, such as eddies and tides, influence the sub-mesoscale oceanography. Strong forcing and complex bathymetry generate three dimensional circulation patterns and sound speed fields. Internal bores, solitons and buoyant jets are some of the phenomena that require nonhydrostatic hydrodynamical models and 3D acoustical models for accurate prediction. In other cases, such as moderately homogeneous internal wave fields, hydrostatic models and 2D acoustic models can capture much of the variability. The aspect ratio, a=h/L, of the flow is the critical parameter. For aspect ratios near one, nonhydrostatic dynamics and 3D acoustics are required. As the long wavelength limit is approached, the hydrostatic assumption and 2D acoustics are sufficient. Recent research programs have focused on observations and modeling of submesoscale oceanographic phenomena, acoustic propagation and acoustic system performance in continental shelf/slope environments. We encourage the presentation of results from observational, modeling and laboratory studies that address these issues. Particular areas of interest are combined hydrodynamical/acoustical simulations including nonhydrostatic and hydrostatic dynamics, with 2-D and 3-D acoustic modeling, and integrating mesoscale and submesoscale ocean models.