Report On Unprecedented Upwelling
On U.S. West Coast During 1999
Current Status of Accomplishment or Milestone: A manuscript is being prepared for submission to EOS that summarizes the unusually high upwelling seen during spring-summer 1999 along the U.S. west coast.
Background: The coastal upwelling index produced by PFEL indicates that coastal upwelling along much of the US west coast in 1999 was the highest in the 50+ years of the index. This goes along with extremely cold ocean temperatures through most of the summer off California, and may be related to a sustained La Niņa event occurring in the tropics since mid-1998.
Purpose of Activity/Goal of Project: Monitoring environmental variability using common physical variables and indices such as SST, wind, and coastal upwelling provides resource managers and researchers a guide to variations that affect ecosystem structure and marine populations. This report will highlight the unusually high upwelling identified from the data sets and products routinely prepared and analyzed by PFEL, augmented with data from other sources (e.g., University of Hawaii, SIO, NOAA CDC and NODC, Tiburon Lab). It will summarize this unusual event in a public forum. These unusual conditions also provide a great opportunity to test our hypotheses on the mechanisms responsible for climate change in the extratropics.
Description of Accomplishment and Significant Results: The analysis and interpretation of 1999 has been completed, in the context of the anomalous conditions that occurred in association with the 1997-98 El Niņo. Through much of spring-summer 1999, an unusually strong North Pacific High led to anomalously high alongshore upwelling-favorable winds in the California Current (CCS). Upwelling for the 1999 season at 36-42°N was the strongest in the 54-year record, and followed a period of weaker upwelling in 1998. SSTs dropped dramatically from Pt. Conception to the Oregon border in April and May 1999, to below 8°C (normally found near 200m depth) at some locations. Temperatures and salinities in the upper 200m off central California, measured during the Tiburon Laboratory's young-of-the-year rockfish surveys in May, were 1-2°C cooler and S=.2-.4 higher (1-2 std. dev.) than the long-term means. Anomalously low sea level since April 1999 agrees with upwelling anomalies. Sea level along northern California in 1999 was the lowest in the 25-year record for this season. Regional wind anomalies led to unprecedented rates of coastal upwelling and extreme SST and sea level anomalies in the CCS.
Significance of Accomplishment (e.g., to the Center, to Management, and to NMFS Strategic plan Goals): The analysis indicates the California Current ecosystem, home to a number of commercially important fish and protected marine mammals, is experiencing very unusual conditions that are likely to affect the distribution, abundance and reproductive capabilities of these species and their prey. This may be a short-lived phenomenon, possibly part of the El Niņo/La Niņa cycle. However it could represent a climatic regime shift to increased upwelling and cooler conditions, analogous to that seen in 1977, which may lead to major long-term shifts in ecosystem structure. Some biological shifts in species composition and distribution already have been reported at CalCOFI and other meetings.
Key Contact: Frank Schwing (831-648-9034, fschwing@pfeg.noaa.gov)