Develop a Biologically Effective Upwelling and Transport Index (BEUTI)

Current Status of Accomplishment or Milestone: Development of this index is still in progress.

Background: The standard upwelling index developed at Pacific Fisheries Environmental Laboratory has long been a workhorse in studies of physical-biological coupling in the world’s eastern boundary current systems. This index is derived exclusively from geostrophic estimates of wind stress on the ocean, hence does not contain relevant information on the properties of the ocean water being upwelled. An improved upwelling index would account for variations in water column structure, including mixed layer depth, strength of stratification, and nutrient concentration, all of which could impact the biological utility of newly upwelled waters.

Purpose of Activity/Goal of Project: This work seeks to examine the relationships between water column structure and the biological utility of coastal upwelling. The ultimate objective is a new upwelling index that better represents the physical forcing of lower-trophic productivity.

Description of Accomplishment and Significant Results: Several steps have been taken towards the development of BEUTI. The first is the completion of a manuscript on seasonal and long-term trends in stratification in the California Current, which will be submitted to a peer-reviewed journal shortly. Results from this analysis are being used to quantify the relationships between wind-forcing and water column structure, and will be used to augment comparisons between the standard upwelling index and biological time series (e.g., CalCOFI zooplankton). A second study is utilizing satellite-derived sea surface temperatures and chlorophyll concentrations as tracers of newly upwelled waters.

Significance of Accomplishment (e.g., to the Center, to Management, and to NMFS Strategic plan Goals): The research accomplished thus far has revealed the importance of water column stratification on the biological utility of upwelling. Increased stratification and a deeper thermocline in parts of the California Current appear to have mitigated the effectiveness of a long-term increase in upwelling-favorable winds. An operational BEUTI will greatly assist efforts to understand how environmental variability can impact marine ecosystems, including commercially-relevant fish stocks on the U.S. West Coast.

Problems: No significant problems. Research on the development of BEUTI will continue in FY04.

Key Contact: Steven Bograd (831-648-8314, sbograd@pfeg.noaa.gov)