GLOBEC 2000: Seasonal and Interannual Variability of the Alaska Coastal Current: Long-Term, Three-dimensional Observations using a Telemetering, Autonomous Vehicle
Craig Lee and Charles Eriksen (both at University of Washington)

A five-year program of physical and biological measurements is proposed to study the seasonal and interannual variability of the Alaska Coastal Current (ACC). The dynamics of the ACC govern stratification and circulation over the inner portion of the Alaska continental shelf, a region that plays a critical role in the early life history of several commercially important fish species, including juvenile salmon. The system resonds strongly to large seasonal and interannual changes in freshwater discharge and wind-forcing. Moreover, seasonal shifts in dynamics likely exert strong infuences on the temporal and spatial structure of stratification, on the spring phytoplankton bloom and on the advective transport of zooplankton and fish. Seasonal cycles in dynamics may also play a key role in explaining how nutrients are replenished in this downelling-favorable system that is inundated by nutrient-deplete freshwater discharge. Thus, variability in wind-forcing and freshwater discharge produce significant changes in ACC dynamics which can influence the recruitment success of zooplankton and fish through a number of different pathways. The proposed study will focus on understanding:

• Seasonal and interannual variability in ACC freshwater content and transport
• The ACC's role in governing springtime mixed layer evolution over the shelf
• Processess controlling temporal and spatial variability in the spring bloom
• Processes that may produce onshore nutrient flux

These processes are inherently three-dimensional and exhibit a wide range of temporal scales. To address these sampling requirements, this program will exploit the capabilities of new, autonomous, telemetering vehicles (Seagliders) to make continuous, high-resolution sections of the ACC. Seagliders measure temperature, conductivity, pressure, chlorophyll fluorescence, dissolved oxygen and backscatter, profiling from the surface to within 10 m of the shelf bottom with 2 km horizontal resolution. A Seaglider will be operated year-round, repeating a sampling pattern designed to provide five sections across the ACC every twenty days. The sampling strategy was designed in coordination with other Long Term Observation Program (LTOP)) investigators to augment existing and proposed LTOP components. The temporal and spatial resolution provided by Seaglider surveys will resolve processes such as springtime restratification and phytoplankton blooms, while the multi-year extent of these observations will explore the system's response to long timescale perturbations in forcing.

This page was last updated on October 31, 2000.

Maintained by:
Hal Batchelder [hbatchelder@coas.oregonstate.edu
College of Oceanic & Atmospheric Sciences
Oregon State University
Corvallis, OR 97331-5503
phone: 541-737-4500; FAX 541-737-2064