Comparison of upwelling indices off Baja California derived from three different wind data sources

This report is not copyrighted. The definitive version was published in California Cooperative Oceanic Fisheries Investigations Reports 48 (2007): 204-214.We compared the NOAA Southwest Fisheries Science Center’s Environmental Research Division (formerly Pacific Fisheries Environmental Laboratory: PFEL) coastal upwelling indices along the northern Baja California coast with those derived from winds measured by coastal meteorological stations and estimated by the QuikSCAT satellite. With the exception of the PFEL series at 33°N, the three data sets compare reasonably well, having similar typical year patterns, correlations >0.6, and significant coherences for periods three to five days or longer. By contrast, the seasonal variations, the timing and magnitude of maximum upwelling, and the variability of the PFEL indices at 33°N are significantly different compared to all the other time series, including QuikSCAT at that location. The performance of the QuikSCAT winds close to shore was evaluated using the coastal meteorological station data. Although large root-meansquare (RMS) errors in direction were found for the QuikSCAT winds, both datasets have properties similar to the variance ellipses, and show reasonable coherences for frequencies in the weather band and lower, particularly south of 33°N.This project was partially funded by the U.S. National Science Foundation through grants to J. P. and M. L

Long-Period Transport Changes in the Eastern North Atlantic and Their Simulation by Propagating Waves

An analysis is presented of geostrophic volume transport across a zonal line along 28-degrees-N in the eastern Atlantic. The data are from an array of five moorings with 200-km spacing carrying temperature sensors and one current meter each for 1 or 2 years. Transport changes in the main thermocline relative to a fixed depth level are obtained by the use of temperature-salinity relationships. The transport variability is simulated by two propagating waves with first-order baroclinic mode structure. Solutions exist with annual and semi-annual periods and zonal wavelengths of 100-200 km and 300 km, respectively. Assuming quasi-geostrophic dynamics and using results on the Reynolds stress, the dominating waves of annual and semi-annual period are found to propagate to the southwest, with 45-degrees-60-degrees and 25-degrees to the south off the westward direction, respectively. Wave solutions with a 90-day period and a zonal wavelength of about 300 km are interpreted as an effect of barotropic waves arising due to horizontal temperature inhomogeneity. The propagation is about +/-25-degrees off the westward direction. In general, good approximations are obtained with the propagating wave simulations in the western and central part of the array, while large differences occur between observation and simulation close to the Canary archipelago. Possible causes for these differences are discussed

Hydrographic conditions near the coast of northwestern Baja California : 1997–2004

Author Posting. © The Authors, 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Continental Shelf Research 26 (2006): 885-901, doi:10.1016/j.csr.2006.01.017.The effects of the 1997-98 and 2002-04 El Ni˜no on the upper waters in the con- tinental shelf and slope regions off northwestern Baja California are explored with data from eight cruises taken in late spring from 1998 to 2004 and the summers of 1997 and 1998. Geostrophic velocities were calculated referenced to a specific vol- ume anomaly surface separating the southward flowing California Current waters from the waters advected to the north by the California Undercurrent. The result- ing fields show equatorward flow near the surface except in the summer of 1997, when a poleward jet was found in the upper 40 dbars. This shallow jet advected anomalously warm and salty waters characteristic of the 1997-98 El Ni˜no, with its core found within 20-30 kms from the coast. By spring of 1998, the waters brought into the region by the jet had mixed across the pycnoline with the salty California Undercurrent waters below, resulting in high salinity levels on the density surfaces corresponding to the otherwise fresh California Current waters (25-26¾t). By con- trast, the 2002-04 El Ni˜no stands out for the very fresh and cold waters found on the same density surfaces in late spring of 2003 and 2004, marking a pronounced presence of subarctic waters. The fresh conditions found on the latter years repre- sent a nearshore expresion of the anomalous intrusion of subarctic waters observed 50-150 km from the coast of Southern California and Punta Eugenia, reported from July 2002 until April 2003. Our results suggest that the presence of this intrusion has continued to influence the region at least until May 2004.This work was supported by the US NSF (OCE-9986627 and OCE-0083976)

Seismic Expression of Pleistocene Paleoceanographic Changes in the California Borderland from Digitally Acquired 3.5 Khz Subbottom Profiles and Ocean Drilling Program Leg 167 Drilling

We correlate processed 3.5 kHz seismic profiles with physical properties of cores collected during ODP Leg 167 from the Tanner, East Cortes, and San Nicolas Basins through much of the Pleistocene succession. Results indicate that seismic horizons in the unconsolidated Pleistocene sediments (top 50 m) are mainly controlled by density contrasts. Removing of the compaction trend from the density reveals a very interesting relationship between density and composition - the density closely and inversely correlates with organic carbon indicating that large-scale variations in organic carbon are responsible for seismic reflections through their influence on density. This is a significant discovery since there apparently is no other paleoceanographic setting that we know of where such a close linkage between acoustic properties and organic carbon has been established. The variations in organic carbon are mainly marine in origin and derive from variations in primary productivity associated with upwelling and the preservation regime related to oxygenation of water. Pleistocene reflections on 3.5 kHz profiles in the Borderland province thus record regional cyclical fluctuations in the paleoclimatic signals. The close resemblance in the density profiles at the three different basins indicates that the sedimentary regime was similar in those basins through the Pleistocene. These common density patterns produce regional seismic horizons that correlate well among the basins. It is likely these correlated and dated horizons could be extrapolated to other Borderland basins (e.g., San Clemente), where they can potentially be used as time markers for neotectonic studies in the region