HR: 16:30h
AN: OS24B-03 INVITED     [Abstracts]
TI: Temporal Trends In Apparent Oxygen Utilization In The Upper Pycnocline Of The North Pacific
AU: * Emerson, S R
EM: emerson@u.washington.edu
AF: School of Oceanography, University of Washington , Settle, WA 98195 United States
AU: Watanabe, Y W
EM: yywata@ees.hokudai.jp
AF: Graduate School of Environmental and Earth Science, Hokkaido University, Sapporo, 060-0810 Japan
AU: Ono, T
EM: tono@fra.affrc.go.jp
AF: Hoddaido National Fisheries Research Institute, 116, Katsurakoi, Kushiro, 085-0802 Japan
AU: Mecking, S
EM: smecking@whoi.edu
AF: Woods Hole Oceanographic Institution, Department of Physical Oceaongraphy, Woods Hole, MA 02543 United States
AU: Deutsch, C
EM: cdeutsch@u.washington.edu
AF: School of Oceanography, University of Washington , Settle, WA 98195 United States
AB: We present a compilation of apparent oxygen utilization (AOU) changes observed in the upper pycnocline of the north Pacific Ocean over the last several decades. The general trend along repeat cross sections of the eastern and western subtropical ocean and the subarctic ocean is an increase in AOU from the mid 1980s to the mid 1990s. AOU has also been increasing in a time-series study in the northwest subarctic ocean off of Japan since the late 1960s. Observed AOU changes south of 35$\deg$N in the subtropical ocean are 10 to 20 $\micron$ol kg$^{-1}$, with much greater changes, reaching 60 to 80 $\micron$ol kg$^{-1}$ in isolated areas, in the subtropical/subarctic boundary and the subarctic ocean. Analysis of changes in both AOU and salinity on isopycnals suggests that there are significant salinity-normalized increases that must be due to alteration in the rate of ventilation, circulation or organic matter degradation. A common feature in the data is that the maximum increase in AOU is centered near the density horizon $\sigma_{\theta}$ = 26.6. Time series results from the Oyashio Current region near the winter outcrop area of this density horizon indicate that surface waters there have become fresher with time, which may mean this density surface has ceased to outcrop in the latter decades of the 20th century. A model description of the cause of these changes is described in a companion abstract in this session. Future determinations of the oxygen concentrations along these transects will be necessary to verify the suggested causes and help determine the role of anthropogenic influences.
DE: 4805 Biogeochemical cycles (1615)
DE: 4806 Carbon cycling
DE: 4845 Nutrients and nutrient cycling
DE: 4215 Climate and interannual variability (3309)
DE: 4532 General circulation
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting