Showing papers by "Heidi M. Dierssen published in 2000"

Bio‐optical properties and remote sensing ocean color algorithms for Antarctic Peninsula waters

Abstract: Increasing evidence suggests that bio-optical properties of Antarctic waters are significantly different than those at temperate latitudes. Consequently, retrieval of chlorophyll concentrations from remotely sensed reflectance measurements using standard ocean color algorithms are likely to be inaccurate when applied to the Southern Ocean. Here we utilize a large bio-optical data set (>1000 stations) collected in waters west of the Antarctic Peninsula in conjunction with the Palmer Long Term Ecological Research program to assess ocean optical properties and associated ocean color algorithms. We find that the remote sensing reflectance spectrum as a function of chlorophyll concentrations appears significantly different from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Bio-optical Algorithm Mini-workshop data set collected from other regions of the world's oceans. For Antarctic waters, remote sensing reflectance is significantly higher in the blue region and lower in the green region of the spectrum for high chlorophyll concentrations (>1 mg Chl m -3 ). Therefore applying general processing algorithms for both Coastal Zone Color Scanner and SeaWiFS in these Antarctic waters results in an underestimate of chlorophyll by roughly a factor of 2. From modeled estimates of absorption and backscattering we hypothesize that both low chlorophyll-specific absorption and low backscattering contribute to the high reflectance ratios.

Optimizing models for remotely estimating primary production in Antarctic coastal waters

Abstract: Primary productivity and associated biogeochemical fluxes within the Southern Ocean are globally significant, sensitive to change and poorly known compared to temperate marine ecosystems. We present seasonal time series data of chlorophyll a, primary productivity and in-water irradiance measured in the coastal waters of the Western Antarctica Peninsula and build upon existing models to provide a more optimum parameterization for the estimation of primary productivity in Antarctic coastal waters. These and other data provide strong evidence that bio-optical characteristics and phytoplankton productivity in Antarctic waters are different from temperate waters. For these waters we show that over 60% ofthe variability in primary production can be explained by the surface chlorophyll a concentration alone, a characteristic, which lends itself to remote sensing models. If chlorophyll a concentrations are accurately determined, then the largest source of error (13-1 8%) results from estimates of the photoadaptive variable (PBo,,>. Further, the overall magnitude of PBopt is low (median 1.09 mg C mg chl-l h-l) for these data compared to other regions and generally fits that expected for a cold water system. However, the variability of PBopt over the course of a season (0.4 to 3 mg C mg chl-I h-I) is not consistently correlated with other possible environmental parameters, such as chlorophyll, sea surface temperature, incident irradiance, day length, salinity, or taxonomic composition. Nonetheless, by tuning a standard depth-integrated primary productivity model to fit representative PBOp, values and the relatively uniform chlorophyll-normalized production profile found in these waters, we can improve the model to account for approximately 72-73% variability in primary production both for our data as well as for independent historic Antarctic data.