TITLE:   Palmer LTER: Temporal and Spatial Variability of Dissolved Inorganic
         Carbon, Oxygen Saturation and Partial Pressure of Carbon Dioxide in
         Surface Waters West of the Antarctic Peninsula
AUTHORS: C. J. Carrillo and D. M. Karl
DATE:    31 Aug - 4 Sep 1998
PLACE:   VII SCAR International Biology Symposium in New Zealand
         Workshop on Long Term Ecological Research in Antarctica 

         Christopher J. Carrillo, School of Ocean & Earth Sciences and 
	 Technology, University of Hawaii
         David M. Karl, School of Ocean & Earth Science and Technology,
	 University of Hawaii

ABSTRACT:
Chemical, physical and biological controls on in-situ dissolved inorganic
carbon (DIC) concentrations, oxygen (O2) saturation and partial pressure
of carbon dioxide (pCO2) in surface water induce temporal and spatial
habitat variability. The Palmer Long-Term Ecological Research (LTER)
Program was established in 1990 to study the Antarctic marine ecosystem in
the area West of the Antarctic Peninsula, especially habitat variability
and response to global climate change (Smith et al. 1995).  Our component
of this multi-disciplinary project is entitled "Microbiology and carbon
flux", and includes measurements of C and O inventories (dissolved gases
and solutes), C and O fluxes (production, particle export and air-to-sea
gas exchange) and microbial community structure and function. This poster
summarizes one aspect of this broader set of research objectives.
 DIC, O2 and pCO2 show large interannual and spatial variability
throughout the region. During the austral summer LTER field seasons
(1996-1998), surface water measurements of pCO2 showed large onshore to
offshore gradients relative to interannual variations. Depending on the
year, pCO2 gradients (ocean-to-atmosphere) ranged from         -260 matm
(undersaturation with respect to the atmosphere) in Marguerite Bay to +50
matm (supersaturation with respect to the atmosphere) in offshore, open
ocean waters. Between 1996 and 1998, the relative area of supersaturated
surface waters increased from offshore to onshore throughout the LTER
study region. Surface water oxygen saturation ranged from 93% to 140% with
respect to atmospheric concentrations.  During the 1993 and 1996 field
seasons, supersaturated O2 surface water prevailed throughout the study
area. In the 1994 and 1995 field seasons, however, undersaturated O2
surface water occurred through much of the area.  We believe these changes
result from hydrographic variations. Between 1993 and 1996, normalized DIC
(to a salinity of 33.5) showed little correlation with measured O2
concentrations. Normalized DIC concentrations ranged from 2159 mmol/kg to
2045 mmol/kg.   Combining the records of O2 saturation and pCO2 saturation
shows a 2-year cycle, where regions oscillate between supersaturated and
undersaturated surface water concentrations with respect to each
parameter. The magnitude and timing of sea-ice throughout the LTER region
and fluctuations in the amount of Antarctic Circumpolar Water upwelled
onto the shelf may explain the interannual and spatial variability shown
here. 

References
Smith R.C., Baker K.S., Fraser W. R., Hofmann E. E., Karl D.M., Klink J.
M., Quetin L. B., Prezelin B. B., Ross R. M., Trivelpiece W. Z., Vernet M.
1995. Oceanography 8, 77-86.