US-GLOBEC NEP Phase IIIb-CGOA: Bottom-up Control of Lower-trophic Variability: A Synthesis of Atmospheric, Oceanic, and Ecosystem Observations
N. Bond, C. Mordy [Both at University of Washington], J. Napp [NOAA Alaska Fisheries Science Center], P. Stabeno [NOAA Pacific Marine Environmental Laboratory]

Project Summary

Data collected as part of CGOA GLOBEC and by other Gulf of Alaska programs will be synthesized for the purpose of quantifying bottom-up mechanisms impacting zooplankton community structure and abundance in the northern Gulf of Alaska (GOA). This work will feature a test of the hypothesis that lower-trophic level production during summer (after the spring bloom) is crucial to the marine ecosystem of the northern GOA shelf, and that fluctuations in production can be linked to atmospheric and physical forcing. The organizing principle of our investigation is that there are two principal factors that determine the properties of the water over the GOA shelf: (a) its source(s) and (b) the cross-shelf and vertical exchanges (mixing) to which it is subjected. The specific mechanisms that will be assessed involve the control of water sources and exchanges, and in turn, their impact on nutrient concentrations, primary production (both amount and species type), and ultimately, zooplankton communities. This assessment will be based on data collected from moorings, drifting buoys and ships, and integrated with results from numerical atmospheric, hydrographic and NPZ models. Comparisons will be made between the eastern (the Seward line), central (off Gore Point) and western (near Kodiak Island) portions of the study area, in the context of the state of the entire northern GOA. The physical and chemical part of the analysis will feature budget calculations of momentum, heat, salts and nutrients, in terms of both seasonal means and episodic events for the GLOBEC years. These results will be used in the analysis and interpretation of the bio-acoustic data from moorings and direct plankton observations from ships, and of simulations from numerical ocean models.

The physical elements of the system are expected to relate to both summertime air-sea interactions and the previous winter's weather, especially as pertaining to snowpack and hence the following warm season's runoff. The proposed project will yield understanding and indices of the atmospheric forcing, and physical and chemical ocean processes, that determine the CGOA primary and secondary production. It will provide valuable data sets for the validation of NPZ models, indicate whether particular regions of the shelf have predictable levels of production and characteristic plankton communities, and provide new insight on where to locate future observation system stations in the northern GOA. Although the program does not include explicit consideration of salmon, it will provide indices relating to ecosystem health that are necessary to understand interannual variability in recruitment success of pink salmon (Oncorhynchus gorbuscha). Here the focus will be on the feeding conditions that appear to enhance the probability for a successful year class (i.e. small phytoplankton cell dominated food webs that support mucous net feeders, larvacae and pteropods). Through enumeration of key aspects of the atmospheric and physical oceanographic forcing and lower-trophic level response, this program will yield critical information for a regional ocean observing system, namely, the parameters to measure, the critical spatial and temporal scales of measurement, and the indices necessary for an ecosystem approach to resource management.

Intellectual merit - Improved understanding of the mechanisms linking climate variability to the marine ecosystem is the core objective of the GLOBEC program. The proposed work will yield specific, quantitative information on these linkages for the shelf region of the northern GOA. This information should help guide improvements in physical and lower-trophic level modeling, and will be valuable for the pan-regional synthesis phase of GLOBEC.

Broader impacts - The results will be shared with fishery resource and ecosystem managers (North Pacific Fishery Management Council and the State of Alaska), and should prove highly useful in planning an ocean observing system for Alaskan waters (Oceans.US). The project includes a post-doctoral researcher and hence the professional development of a recent graduate.

This page was last updated on March 14, 2007.

Maintained by:
Hal Batchelder
College of Oceanic and Atmospheric Sciences
Oregon State University
Corvallis, OR 97331-5503
phone: 541-737-4500; FAX 541-737-2064