Correlations between the satellite‐derived seasonal cycles of phytoplankton biomass and aerosol optical depth in the Southern Ocean: Evidence for the influence of sea ice

Abstract

[1] The relationship between the production of dimethylsulfide (DMS) in the upper ocean and atmospheric sulfate aerosols has been confirmed through local shipboard measurements, and global modeling studies alike. In order to examine whether such a connection may be recoverable in the satellite record, we have analyzed the correlation between mean surface chlorophyll (CHL) and aerosol optical depth (AOD) in the Southern Ocean, where the marine atmosphere is relatively remote from anthropogenic and continental influences. We carried out the analysis in 5-degree zonal bands between 50°S and 70°S, for the period (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004), and in smaller meridional sectors in the Eastern Antarctic, Ross and Weddell seas. Seasonality is moderate to strong in both CHL and AOD signatures throughout the study regions. Coherence in the CHL and AOD time series is strong in the band between 50°S and 60°S, however this synchrony is absent in the sea-ice zone (SIZ) south of 60°S. Marked interannual variability in CHL occurs south of 60°S, presumably related to variability in sea-ice production during the previous winter. We find a clear latitudinal difference in the cross correlation between CHL and AOD, with the AOD peak preceding the CHL bloom by up to 6 weeks in the SIZ. This suggests that substantial trace gas emissions (aerosol precursors) are being produced over the SIZ in spring (October-December) as sea ice melts. This hypothesis is supported by field data that record extremely high levels of sulfur species in sea ice, surface seawater, and the overlying atmosphere during ice melt.Citation: Gabric, A. J., J. M. Shephard, J. M. Knight, G. Jones, and A. J. Trevena (2005), Correlations between the satellite-derived seasonal cycles of phytoplankton biomass and aerosol optical depth in the Southern Ocean: Evidence for the influence of sea ice, Global Biogeochem. Cycles, 19, GB4018,

The CLAW hypothesis: a review of the major developments

“…MSA is thought to be a more or less conservative marker for DMS and lower MSA correlates with a lower extent of sea ice, because waters covered by sea ice in winter tend to be highly biologically active after sea ice melt, and a major source of DMS and hence MSA. [90,91] Satellite observations have shown that since 1950 the extent of the sea ice has diminished, corresponding to a decrease in MSA in the ice core, [90] which could imply a reduction in DMS emissions. [91,92] The modelling study of Sarmiento et al [93] suggests that as surface temperatures increase with increasing carbon dioxide, there will be an increase in primary productivity of between 0.7 and 8.1%.…”

“…[90,91] Satellite observations have shown that since 1950 the extent of the sea ice has diminished, corresponding to a decrease in MSA in the ice core, [90] which could imply a reduction in DMS emissions. [91,92] The modelling study of Sarmiento et al [93] suggests that as surface temperatures increase with increasing carbon dioxide, there will be an increase in primary productivity of between 0.7 and 8.1%. However, there would be major shifts from currently productive regions to other ocean regions.…”

Characterization of the inter-annual, seasonal, and diurnal variations of condensation particle concentrations at Neumayer, Antarctica

“…Nevertheless, there is some observational evidence of considerable particle nucleation within the MBL in regions with enhanced DMS flux (Davison et al, 1996;O'Dowd et al, 1997;Clarke et al, 1998). In this context, the Southern Ocean surrounding the Antarctic continent shows striking biological activity during polar spring and summer (Gabric et al, 2005;Korhonen et al, 2008;Lana et al, 2011), provoking pronounced formation of biogenic sulfur aerosol (Minikin et al, 1998;Preunkert et al, 2007). Accordingly, nucleation events have also been reported from coastal Syowa (Ito, 1993) and the rather coastal Finnish Antarctic station Aboa (73 • 03 S, 13 • 25 W, 130 km away from coastline; Koponen et al, 2003), while at continental South Pole comparable events had to be typically associated with the impact local pollution during calm weather conditions (Park et al, 2004).…”

Fluorescence-Based Approach to Estimate the Chlorophyll-A Concentration of a Phytoplankton Bloom in Ardley Cove (Antarctica)

“…Research seldom applies chlorophyll-a profiles and integrated chlorophyll-a signals to compare in situ and satellite match-ups. Current reports have already shown the obvious underestimation from satellite algorithms [6][7][8][9][10][11]. If considering the deep chlorophyll-a maximum and chlorophyll-a profile, there is a larger underestimation in SO chlorophyll-a retrieval.…”

“…As a result, satellite measurements from space still have large errors in estimating phytoplankton biomass [4,5] and global chlorophyll-a satellite algorithms typically underestimate chlorophyll-a in the Southern Ocean [6][7][8][9][10][11].…”