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367 ␥ storm tracks (Oglesby et al. 1989). The relatively rapid sediment-accumulation rates in the Gulf of Mexico allow development of records with submillennial to decadal resolution . The primary surface-ocean current in the Gulf of Mexico is the Loop Current that brings warm waters from the Caribbean Sea through the Yucatan Straits into the Gulf of Mexico. The Loop Current exits the Gulf of Mexico into the North Atlantic Ocean through the Straits of Florida. Surface-water and wind circulation in the Caribbean– Gulf of Mexico region show large annual changes linked to seasonal migration of the Intertropical Convergence Zone (ITCZ) (Fig. 22.1). During the Northern Hemisphere winter, the ITCZ lies near the equator, and easterly winds from the Atlantic blow onto South America, bringing rains to the Amazon basin. Prevailing westerly surface winds from the Pacific Ocean bring moisture into the west coast of North America. Precipitation in the southwestern United States and eastern Mexico is low (Tang and Reiter 1984). During winter the Loop Current generally does not penetrate into the western or northern Gulf of Mexico. Warm, tropical waters from the Caribbean are usually restricted to the southeastern Gulf of Mexico reflecting the flow of the Loop Current from the Yucatan Straits to the Straits of Florida. However, the penetration of the Loop Current into the northern Gulf of Mexico varies from year to year, and anticyclonic eddies that break off the Loop Current at irregular intervals can bring warm waters to the northern and central Gulf of Mexico during some winters (Müller-Karger et al. 1991). Planktic foraminifers are commonly used as proxies in paleoceanographic studies. Information on assemblages and variations in the abundance of individual taxa is used to estimate surface-water temperature, identify the influence of currents and water masses, and infer structure in the upper part of the water column (thermocline depth) (e.g., Imbrie and Kipp 1971; Brunner 1979; Ravelo et al. 1990). In addition, measurement of the isotopic and trace-element composition of foraminifer tests is being used to obtain quantitative estimates of temperature and salinity in past oceans (e.g., Elderfield and Ganssen 2000). This report presents census data for planktic foraminifer assemblages in 3 cores recovered from the Gulf of Mexico . The census data are being used to determine climate and environmental changes in the Gulf of Mexico and surrounding region for the last 10,000 years (10 ka) (e.g., Poore et al. 2004; Poore et al. 2005). Background The Gulf of Mexico is a semi-enclosed basin at the northwestern edge of the tropical Atlantic Ocean. Information on surface-water and surface-circulation history of the Gulf of Mexico is of interest because the Gulf of Mexico is the source of moisture for a large area of North America, Greenland, and the North Atlantic region (Peixóto and Oort 1983). Sea-surface temperatures (SST) in the Gulf of Mexico determine the amount of water vapor transported out of the Gulf of Mexico and influence North Atlantic 22 Planktic Foraminiferal Relative Abundance and Trends in Gulf of Mexico Holocene Sediments Records of Climate Variability R. Z. Poore, S. Verardo, J. Caplan, K. Pavich, and T. Quinn 368 ~ Poore, Verardo, Caplan, Pavich, and Quinn divided into 2 subzones based on the last occurrence of G. crassaformis but was not sampled or studied in detail. Malmgren and Kennett (1976) did a principal component analysis of the foraminiferal assemblage data from Kennett and Huddleston (1972) and found that the first principal component contrasted warm- and cool-water species . The stratigraphic plot of the coordinates of individual samples in cores along the axis of the first principal component was interpreted as a paleoclimate signal. Brunner (1982) used the transfer function technique of Imbrie and Kipp (1971) to estimate SSTs and salinities extending back through the last interglacial in several cores from the Gulf of Mexico. The quantitative estimates of SST by Brunner (1982) differ in detail from those of previous studies but show the same general pattern. Sample resolution was designed to establish the glacial-interglacial signal. Only a few Holocene temperature estimates were made, although some records show evidence for a mid-Holocene winter temperature maximum (Brunner 1982, her Fig. 8). More detailed information on the character of the Holocene record in the Gulf of Mexico is available from cores from the Orca Basin on the Louisiana slope south of the Mississippi River delta (Fig. 22.1). As part of studies into the impact of meltwater influx into...

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