THE CONSORTIUM ON THE OCEAN'S ROLE IN CLIMATE
Link to NOAA Strategic Plan: NOAA's Mission Goal 2: Understand Climate Variability and Change to Enhance Society's Ability to Plan and Respond
RESEARCH OBJECTIVES AND SPECIFIC PLANS TO ACHIEVE THEM
The objectives of the Consortium on the Ocean’s Role in Climate (CORC) are (1) to maintain critical elements of the ocean climate observing system in the Pacific Ocean and disseminate descriptions of observed climate variability, (2) to develop new observational and data-assimilation methods for documenting and diagnosing climate change in the ocean, and (3) contribute to the assessment of climate change and the predictability of climate variability.
During this no-cost-extension period CORC’s progress met expectations. Basin-scale high-quality Voluntary Observing Ship (VOS) measurements of ocean structure and transport, surface-temperature and surface current measurements by drifters provided quantitative measures of how the ocean participates in broad-scale climate variability. A Spray underwater glider continued monitoring the Pacific’s South Equatorial Current between New Caledonia and the Solomon Islands as it feeds the climatically important equatorial current system. A data-assimilating model, which is being developed to integrate disparate ocean climate observations, was extensively tested over the calendar year 2000 and a study of the impact of California Current sea-surface temperature on temperatures in the western U.S. was completed. The previously developed Underway CTD and Spray glider were made commercially available.
RESEARCH ACCOMPLISHMENTS
Quarterly High Resolution eXpendable (HRX) transects were maintained along basin-spanning routes that include:
PX37/10/44 (North Pacific – San Francisco to Hawaii to Guam to Hong Kong)
PX38 (North Pacific – Hawaii to Alaska)
PX08 (South Pacific – New Zealand to Panama)
PX06/31 (Central Pacific – New Zealand to Fiji to Los Angeles)
PX30 (South Pacific – Brisbane to Fiji, joint with CSIRO Australia)
IX15/21 (South Indian – Fremantle to Mauritius to Durban)
Logistical assistance or XBT probes are provided collaboratively for:
PX34 (South Pacific – Wellington to Sydney, CSIRO Australia)
IX28 (Southern Ocean – Hobart to Antarctica, CSIRO Australia)
AX22 (Southern Ocean – Drake Passage)
During each cruise, XBT temperature profiles (0-800 m) are collected at spatial intervals from 10 km near ocean boundaries and the equator, to 50 km in interior regions – resolving boundary currents and interior eddies for calculation of ocean-wide integrals of geostrophic transport. A web site for the project, with downloadable data, is maintained at http://www-hrx.ucsc.edu. HRX data are transmitted on the GTS immediately after collection for real-time applications. Due to the rapidly evolving nature of the present-day commercial shipping industry, a strong focus of the work has been to maintain sampling along routes as ships and shipping companies change.
Surface drifter (Niiler) sampling of surface currents and surface temperature were maintained as part of the Surface Velocity Program.
A Spray glider completed a second crossing of the Pacific’s South Equatorial Current (SEC) from Guadalcanal, Solomon Islands to New Caledonia. While good data was obtained for part of this section, fish bite became, for the first time, an identified operational problem. Two separate strikes, separated by weeks, first damaged the glider’s vertical stabilizer causing erratic flight and making the vertically integrated velocity measurements dubious, and then introduced a shift into the CTD calibration. A paper describing the first crossing was accepted for publication.
A second glider was prepared for deployment from an IRD, Noumea cruise off New Guinea from which point it will transit the Solomon Sea to Guadalcanal for recovery. This is planned as the first of 4 sections across the low-latitude western boundary current that connects the SEC to the climatically critical equatorial zone.
Cornuelle (SIO), Stammer (SIO/IFM), and Hoteit (SIO) are using the data-assimilating ECCO-MITGCM model to synthesize observations in the tropical Pacific Ocean into a coherent description of climate variability. Over 135 iterations of the year 2000 assimilation have been run, significantly improving the fit to the observations compared with forward runs. Most tropical Pacific observations were used: altimeter SSH, TMI SST, climatological T & S profiles, TAO, XBT, CTD, ARGO, and drifters, as well as Johnson's analysis of mean currents. The model evolution is now being studied to diagnose the dynamics of the tropical Pacific, and gives a realistic testbed for evaluating theories of the tropical circulation, such as the Equatorial Undercurrent (EUC) dynamical balances, and the predictability of tropical instability waves (TIW). A paper describing these results is in preparation.
Air temperature anomalies in the western United States have important impacts, including effects on energy demand and human health. Monthly SST anomalies averaged over the California Current were found to be positively correlated at modest magnitudes with monthly continental surface air temperature fluctuations. Basin scale Pacific SST is known to be linked to continental air temperature anomalies, but a strictly coastal influence also appears to operate. This was demonstrated in a study by Cayan using correlations of California Current SST with air temperature recorded at hundreds of cooperative weather stations, most spanning a time period beginning in 1948. To remove possible remote effects from basin scale SST influences, the Pacific Decadal Oscillation (PDO) was removed, via linear regression, from the California Current SST. The spatial extent of the SST influence varies with season and other factors, but in many cases, correlations tend to decay beyond about 200 km from the coastline. The SST influence persists for a few to several months, and shows up in both daytime and nighttime air temperature fluctuations.
