Cruise info
===========
Ocean/Atmosphere Exchange of Trace Compounds cruise 1992 (OAXTC 92)

The main goal of this study was to determine the atmospheric mixing ratio of 
hydrochlorofluorocarbon (HCFC-22) and its partial pressure in surface waters of 
the West Pacific Ocean to assess the possible existence of an oceanic sink for 
this compound.  

ABSTRACT
========
CFC-11 (CCl3F), CFC-12 (CCl2F2), methyl chloroform (CH3CCl3), carbon 
tetrachloride (CCl4), and HCFC-22 (CHClF2), nitrous oxide (N2O), and 
CFC-113  (CCl2F-CClF2) were measured in the air and surface 
waters of the Pacific Ocean from 55°N to 22°S during the late summer and early 
fall of 1992.  Atmospheric measurements of all gases agreed well with results 
from NOAA fixed stations at similar latitudes.  CFC-11 and CFC-12, which have 
long atmospheric lifetimes and are essentially inert in seawater, responded 
mainly to physical processes in the air and water.  Both gases were 
supersaturated by 2-6% at higher, northern latitudes, reflecting the effects of
radiative warming.  Their saturation anomalies declined southward through the 
tropics and ultimately became slightly negative in the southern hemisphere. 
HCFC-22 showed signs of small losses in the tropics and subtropics, a sink that
may account for 2% of the losses of this gas from the atmosphere.  CH3CCl3 
showed a similar pattern, with only a tropical sink.  This is consistent with 
hydrolysis and, together with data from an earlier expedition, implies that 
about 6% of atmospheric CH3CCl3 is lost to the ocean.  The net saturation anomaly 
for CCl4 was virtually negative everywhere and only slightly dependent upon 
latitude.  This would be expected for a sink that was not particularly 
temperature dependent and it is consistent with evidence from deepwater profiles 
that indicate a sink at depth.  Fluxes calculated from CCl4 saturation anomalies 
indicate that 15-35% of atmospheric CCl4 is lost to the ocean.

List of measured compounds:
===========================
CFC-11 (CCl3F)
CFC-12 (CCl2F2)
Methyl chloroform (CH3CCl3)
Carbon tetrachloride (CCl4)
HCFC-22 (CHClF2)
Nitrous Oxide (N2O)
CFC-113 (CCl2F-CClF2)

Method:
=======
Gas chromatography / electron capture detector (GC/MS)

The Platform:
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R/V John V. Vickers

Contact persons:
================
Juergen M. Lobert +1 303 497 7006 (tel) 7850 (fax)	jlobert@cmdl.noaa.gov
James H. Butler +1 303 497 6898 (tel 6290 (fax)		jbutler@cmdl.noaa.gov


see the World Wide Web homepage for this cruise:

	http://www.cmdl.noaa.gov/noah_home/ocean/oaxtc92.html