Goyet, C. Woods Hole Oceanographic Institution, cgoyet@whoi.edu
Peltzer, E. Monterey Bay Aquarium Research Institute, etp3@mbari.org
Eischeid, G. Woods Hole Oceanographic Institution, geischeid@whoi.edu
Kirchlechner, T. University of Otago, thomas.kirchlechner@stonebow.otago.ac.nz

In order to quantify the role of dissolved organic matter in the global carbon cycle, we measured the total organic carbon (TOC) concentration in discrete samples collected in surface waters and in samples collected throughout the water column. The samples were collected and measured on board the R/V Roger Revelle during cruises conducted as part of the US JGOFS Southern Ocean program. Both cruises departed and ended in Littleton, New Zealand. The cruise during November of 1997, occurred during the austral spring and witnessed the poleward retreat of the marginal ice zone. The January cruise occurred during the austral summer. The measurements were performed using a manual injection high-temperature-combustion technique (Peltzer and Brewer, 1993; Peltzer et al., 1996). Samples were collected from both the underway sampling system and from the CTD rosette casts using 20L Niskin bottles. Following collection, the samples were immediately acidified and stored at 4degC until analyzed. All samples were analyzed on-board to avoid problems with sample preservation and contamination during transport. The data indicate that TOC in surface waters decreases significantly (by approximately 15 umol/L) across the subtropical front area, with higher concentrations north of the front than south of the front. In deep waters, south of the subtropical front, the concentration of TOC is constant at approximately 42 umol/L. This value is consistent with earlier work in the area as well as observations made in the Ross Sea during 1996 and 1997. However, the TOC concentration in the sub-surface and surface waters was approximately 10 to 15 umol/L higher than in the deep waters. While the near surface enrichment was not as large as observed previously in the Equatorial Pacific Ocean (Peltzer and Hayward, 1996) or the Arabian Sea (Hansell and Peltzer, in press) considerable quantities of carbon were tied up in the dissolved organic matter. Additionally, substantial spatial gradients were observed in the mixed-layer distribution. The depth and slope of these gradients vary both in time and space. References: Peltzer, E. T. and P. G. Brewer (1993). Some practical aspects of measuring DOC-sampling artifacts and analytical problems with marine samples. Marine Chemistry 41: 243-252. Peltzer, E. T., B. Fry, P. H. Doering, J. H. McKenna, B. Norrman and U. L. Zweifel (1996). A comparison of methods for the measurement of dissolved organic carbon in natural waters. Marine Chemistry 54: 85-96. Peltzer, E. T. and N. A. Hayward (1996). Spatial and temporal variability of total organic carbon along 140degW in the equatorial Pacific ocean in 1992. Deep-Sea Research II (Equatorial Pacific 2) 43: 1155-1180. Hansell, D. A. and E. T. Peltzer (in press). Spatial and Temporal Variations of Total Organic Carbon in the Arabian Sea. Deep-Sea Research II (US-JGOFS Arabian Sea Special Volume).
Day: Wednesday, Feb. 3
Time: 04:00 - 04:15pm
Location: Sweeney Center
Code: SS31WE0400S