A Synthesis Of In Situ Measured Export Production in the Southern Ocean Book uri icon

abstract

  • The southern ocean is a key region contributing to the regulation of both atmospheric CO sub(2) concentration and deep ocean O sub(2) levels in part through the "biological pump. Although numerous studies on the production and fate of biomass in this region have been carried out in the last two decades, a proper synthesis of the data has yet to be done. We have compiled and carried out a comprehensive analysis of the published POC flux data that were collected using three different techniques moored sediment traps, surface tethered traps and super(234)Th based measurements. All the available POC fluxes have been normalized to 100m using the Martin curve, which predicts carbon attenuation as a function of depth. The dataset can be segregated into three geographical/spatial regions (Atlantic Sector, Pacific Sector and Indian Sector) and two broad temporal regimes -spring (October-December) and summer (January-March). The Pacific and Indian sectors show a large temporal variability in the POC export between spring (95 mg C m super(-2) d super(-1) and 157 mg C m super(-2) d super(-1) respectively) and summer (62 mg C m super(-2) d super(-1) and 43 mg C m super(-2) d super(-1) respectively) but no such temporal variability in POC export between spring (118 mg C m super(-2) d super(-1)) and summer (113 mg C m super(-2) d super(-1)) was observed for the Atlantic sector. Based on the available in situ primary production data, the export efficiency (POC flux: Primary Production) was computed for each of these regions. The average spring time export efficiency for Atlantic, Pacific and Indian sectors were 0.08, 0.37 and 0.13 respectively while during summer the average export ratios were estimated to be 0.27, 0.11 and 0.06 respectively. The overall low export ratio for the Indian sector is due to the fact that all the available data falls to the north of the Polar Front compared with the Atlantic and Pacific sector data, which fall to the south of the Polar Front. Similar spring and summer time POC fluxes in the Atlantic sector can be explained to some extent by the higher biological production and lower export efficiency in spring compared to relatively lower biological production and higher export efficiency in summer. The ultimate goal of this data synthesis is to refine the satellite-derived export flux algorithms with special emphasis on Southern Ocean, which in turn will be used to balance the mixed layer O sub(2) budget and ocean climatologies of dissolved O sub(2). Preliminary model run matchups between monthly satellite based new production and the monthly in situ measured POC flux data are not high but significant. Further analysis needs to be done to effectively assimilate the observational dataset into the model in order to derive a better estimation of export flux that can reproduce the large seasonal and spatial variability associated with this region.

publication date

  • October 2007