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In connection with the Palmer LTER program, mixed layer water samples were collected during the cruise of the L.M. Gould in Jan., 2008 at 49 stations on a 20 × 100 km grid in the West Antarctica Peninsula (WAP) region of the Southern Ocean. In this study, [O2]/[Ar] ratios and the triple isotope composition of dissolved O2 were measured, and were used to estimate net community O2 production (NCP) and gross primary O2 production (GPP), respectively. These estimates are further converted to carbon export production, primary production and the f-ratio. Our measurements give NCP ranging from -3 to 76 mmol O2 m-2 day-1 (-25 to 650 mg C m-2 day-1), and GPP from 40 to 220 mmol O2 m-2 day-1 (180 to 1010 mg C m-2 day-1). The O2 NCP/GPP ratios range from -0.04 to 0.43, corresponding to f-ratios of -0.08 to 0.83. NCP and the NCP/GPP ratio are highest in the northern coastal areas, and decrease to lower values toward the southern coastal area and the open ocean. The inshore-offshore gradient appears to be regulated primarily by iron availability, as supported by the positive correlation between NCP and Fv/Fm ratios (r² = 0.22, p < 0.05). Mixed layer depth (MLD) is inversely correlated with NCP (r² = 0.21, p < 0.002) and NCP/GPP (r² = 0.21, p < 0.02), and highest NCP occurred in the fresh water lenses probably formed from melted coastal glaciers. These results suggest that export production and the f-ratio increase where water stratification is intensified by input of fresh meltwater, and that mixed layer stratification is the major factor regulating NCP in the inner-shelf and coastal regions. Along-shelf variability of phytoplankton community composition is highly correlated with NCP, i.e., NCP increases when the diatom-dominated community in the south transitions to the cryptophyte-dominated one in the north. A high correlation is also observed between NCP and the logarithm of the surface chlorophyll concentration (r² = 0.72, p < 0.0001) , which makes it possible to estimate carbon export as a function of Chl a concentration in this region. [ABSTRACT FROM AUTHOR]

Abstract: Disintegration of the Antarctic Peninsula''s eastern ice shelves has increased the population of icebergs traversing the Weddell Sea, but until recently little was known about their ecological impact on the pelagic environment. Here we describe a class of algal communities that occur on the submerged flanks of large, free-drifting, glacially-derived tabular icebergs. We used remotely operated vehicles to examine these icebergs directly for the first time, to survey the algal communities and collect material for shipboard laboratory studies. The communities, principally diatoms, were associated with a characteristic cupped configuration of the ice surface, and they served as feeding sites for aggregations of Antarctic krill. Production rate measurements indicate that these communities are providing a substantial contribution to regional primary production in summer. As the number of icebergs grows, the number of algae communities may also be increasing, along with their cumulative contribution to organic carbon flux. [Copyright &y& Elsevier]

We describe the results from a spatial cyberinfrastructure developed to characterize the meitwater field around individual icebergs and integrate the results with regionaland global-scale data. During the course of the cyberinfrastructure development, it became clear that we were also building an integrated sampling planning capability across multidisciplinary teams that provided greater agility in allocating expedition resources resulting in new scientific insights. The cyberinfrastructure-enabled method is a complement to the conventional methods of hydrographic sampling in which the ship provides a static platform on a station-by-station basis. We adapted asea-floor mapping method to more rapidly characterize the sea surface geophysically and biologically. By jointly analyzing the multisource, continuously sampled biological, chemical, and physical parameters, using Global Positioning System time as the data fusion key, this surface-mapping method enables us to examine the relationship between the meltwater field of the iceberg to the larger-scale marine ecosystem of the Southern Ocean. Through geospatial data fusion, we are able to combine very fine-scale maps of dynamic processes with more synoptic but lower-resolution data from satellite systems. Our results illustrate the importance of spatial cyberinfrastructure in the overall scientific enterprise and identify key interfaces and sources of error that require improved controls for the development of future Earth observing systems as we move into an era of petaand exascale, data-intensive computing. [ABSTRACT FROM AUTHOR]

The article presents a study which examined the impact of free-drifting icebergs in the Atlantic sector of the Southern Ocean aboard the Antarctic Research and Supply Vessel (ARSV) Laurence M. Gould (LMG) and aboard the Research Vessel Ice Breaker (RVIB) Nathaniel B. Palmer. It describes how the icebergs affect pelagic ecosystem such as physical disruption and the availability of critical nutrients. It discusses the iceberg ecosystem structure and function.

Abstract: Observations near a large tabular iceberg in the Weddell Sea in March and April 2009 show evidence that water from ice melting below the surface is dispersed in two distinct ways. Warm, salty anomalies in T–S diagrams suggest that water from the permanent thermocline is transported vertically as a result of turbulent entrainment of meltwater at the iceberg''s base. Stepped profiles of temperature, salinity, and density in the seasonal thermocline are more characteristic of double-diffusive processes that transfer meltwater horizontally away from the vertical ice face. These processes contribute comparable amounts of meltwater–O(0.1m3) to the upper 200m of a 1m2 water column–but only basal melting results in significant upwelling of water from below the Winter Water layer into the seasonal thermocline, suggesting that these two processes may have different effects on vertical nutrient transport near an iceberg. [Copyright &y& Elsevier]