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Pan, JB, Vernet M, Reynolds RA, Mitchell GB.  2019.  The optical and biological properties of glacial meltwater in an Antarctic fjord. PLOS ONE. 14: Public Library of Science   10.1371/journal.pone.0211107   Abstract

As the Western Antarctic Peninsula (WAP) region responds to a warmer climate, the impacts of glacial meltwater on the Southern Ocean are expected to intensify. The Antarctic Peninsula fjord system offers an ideal system to understand meltwater’s properties, providing an extreme in the meltwater’s spatial gradient from the glacio-marine boundary to the WAP continental shelf. Glacial meltwater discharge in Arctic and Greenland fjords is typically characterized as relatively lower temperature, fresh and with high turbidity. During two cruises conducted in December 2015 and April 2016 in Andvord Bay, we found a water lens of low salinity and low temperature along the glacio-marine interface. Oxygen isotope ratios identified this water lens as a mixture of glacial ice and deep water in Gerlache Strait suggesting this is glacial meltwater. Conventional hydrographic measurements were combined with optical properties to effectively quantify its spatial extent. Fine suspended sediments associated with meltwater (nanoparticles of ~ 5nm) had a significant impact on the underwater light field and enabled the detection of meltwater characteristics and spatial distribution. In this study, we illustrate that glacial meltwater in Andvord Bay alters the inherent and apparent optical properties of the water column, and develop statistical models to predict the meltwater content from hydrographic and optical measurements. The predicted meltwater fraction is in good agreement with in-situ values. These models offer a potential for remote sensing and high-resolution detection of glacial meltwater in Antarctic waters. Furthermore, the possible influence of meltwater on phytoplankton abundance in the surface is highlighted; a significant correlation is found between meltwater fraction and chlorophyll concentration.

Dierssen, HM, Vernet M, Smith RC.  2000.  Optimizing models for remotely estimating primary production in Antarctic coastal waters. Antarctic Science. 12:20-32. AbstractWebsite

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 an different from temperate waters. For these waters we show that over 60% of the 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 13-18) results from estimates of the photoadaptive variable (P-opt(B)). Further, the overall magnitude of P-opt(B) is low (median 1.09 mg C mg chl(-1) h(-1)) for these data compared to other regions and generally fits that expected for a cold water system. However, the variability of P-opt(B) over the course of a season (0.4 to 3 mg C mg chl(-1) h(-1)) 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 P-opt(B) 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.

Diaz, S, Camilion C, Deferrari G, Fuenzalida H, Armstrong R, Booth C, Paladini A, Cabrera S, Casiccia C, Lovengreen C, Pedroni J, Rosales A, Zagarese H, Vernet M.  2006.  Ozone and UV radiation over southern South America: Climatology and anomalies. Photochemistry and Photobiology. 82:834-843.   10.1562/2005-09-26-ra-697   AbstractWebsite

Ozone and UV radiation were analyzed at eight stations from tropical to sub-Antarctic regions in South America. Ground UV irradiances were measured by multichannel radiometers as part of the Inter American Institute for Global Change Radiation network. The irradiance channels used for this study were centered at 305 nm (for UV-B measurements) and 340 nm (for UV-A measurements). Results were presented as daily maximum irradiances, as monthly averaged, daily integrated irradiances and as the ratio of 305 nm to 340 nm. These findings are the first to be based on a long time series of semispectral data from the southern region of South America. As expected, the UV-B channel and total column ozone varied with latitude. The pattern of the UV-A channel was more complex because of local atmospheric conditions. Total column ozone levels of < 220 Dobson Units were observed at all sites. Analysis of autocorrelations showed a larger persistence of total column ozone level than irradiance. A decreasing cross-correlation coefficient between 305 and 340 nm and an increasing cross-correlation coefficient between 305 nm and ozone were observed at higher latitudes, indicating that factors such as cloud cover tend to dominate at northern sites and that ozone levels tend to dominate at southern sites. These results highlight the value of long-term monitoring of radiation with multichannel radiometers to determine climatological data and evaluate the combination of factors affecting ground UV radiation.