HR: 13:55h
AN: OS23F-02    [Abstracts]
TI: Water Mass Property Variability in the Eastern Basin of the North Atlantic Ocean
AU: * Johnson, G C
EM: gregory.c.johnson@noaa.gov
AF: NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE Bldg. 3, Seattle, WA 98115-6349 United States
AU: Bullister, J L
EM: john.l.bullister@noaa.gov
AF: NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE Bldg. 3, Seattle, WA 98115-6349 United States
AU: Gruber, N
EM: ngruber@igpp.ucla.edu
AF: IGPP & Dept. of Atmospheric Sciences, University of California, Los Angeles, CA 90095-4996 United States
AU: Zhang, J
EM: jia-zhong.zhang@noaa.gov
AF: Ocean Chemistry Division, NOAA/AOML, 4301 Rickenbacker Causeway, Miami, FL 33149 United States
AB: A meridional hydrographic section has been occupied from south of Iceland across the equator at least three times over the past two decades. The first occupation was WOCE section A16N in July - August 1988, the second was a NOAA OACES section in July - August 1993, and the third was the first section of the Repeat Hydrography Program in support of the Carbon Cycle and CLIVAR Programs in June - August 2003. Some of the differences between the 2003 and 1988 occupations include: 1. Colder, fresher, denser, more oxygen-rich Labrador Sea Water (LSW) in 2003 compared with 1988. This change, visible between 40$\deg$N and Iceland from 1500 to 3000 dbar, reveals variability in LSW reaching to the eastern basins of the North Atlantic. LSW was more vigorously ventilated in the years leading up to 2003 than in the years prior to 1988, consistent with the water mass property changes. 2. Regional mode waters (indicated by widely spaced isotherms in the vertical starting near 7$\deg$C off Iceland and ending near 14$\deg$C by 32$\deg$N) are warmer and lighter in 2003 compared with 1988, and their associated potential vorticity minimum shifts to lighter, warmer, and shallower horizons north of about 42$\deg$N. The pattern suggests that over a few years prior to 2003 conditions were warmer, and these waters less vigorously ventilated, than prior to 1988. 3. Substantial decreases in oxygen concentration are observed from the base of these mode waters down to the oxygen minimum in 2003 compared with 1988. These changes within the oxycline, strongest from about 40$\deg$N to Iceland, are again consistent with less vigorous ventilation of the local mode waters just above in the years prior to 2003 compared with 1988.
DE: 4805 Biogeochemical cycles (1615)
DE: 4215 Climate and interannual variability (3309)
DE: 4223 Descriptive and regional oceanography
DE: 4283 Water masses
DE: 4504 Air/sea interactions (0312)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting