Vernet Maria

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Vernet
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Maria
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  • Preprint
    Multiscale control of bacterial production by phytoplankton dynamics and sea ice along the western Antarctic Peninsula : a regional and decadal investigation
    ( 2012-03-07) Ducklow, Hugh W. ; Schofield, Oscar M. E. ; Vernet, Maria ; Stammerjohn, Sharon E. ; Erickson, Matthew
    We present results on phytoplankton and bacterial production and related hydrographic properties collected on nine annual summer cruises along the western Antarctic Peninsula. This region is strongly influenced by interannual variations in the duration and extent of sea ice cover, necessitating a decade-scale study. Our study area transitions from a nearshore region influenced by summer runoff from glaciers to an offshore, slope region dominated by the Antarctic Circumpolar Current. The summer bacterial assemblage is the product of seasonal warming and freshening following spring sea ice retreat and the plankton succession occurring in that evolving water mass. Bacterial production rates averaged 20 mgC m-2 d-1 and were a low (5%) fraction of the primary production (PP). There was significant variation in BP between regions and years, reflecting the variability in sea ice, Chlorophyll and PP. Leucine incorporation was significantly correlated (r2 ranging 0.2-0.7, p<0.001) with both chlorophyll and PP across depths, regions and years indicating strong phytoplankton-bacteria coupling. Relationships with temperature were variable, including positive, negative and insignificant relationships (r2 <0.2 for regressions with p<0.05). Bacterial production is regulated indirectly by variations in sea ice cover within regions and over years, setting the levels of phytoplankton biomass accumulation and PP rates; these in turn fuel BP, to which PP is coupled via direct release from phytoplankton or other less direct pathways.
  • Dataset
    Production vs Irradiance data from RVIB Nathaniel B. Palmer cruise NBP0103 in the Southern Ocean in 2001 (SOGLOBEC project)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-05) Vernet, Maria
    Production vs Irradiance data from RVIB Nathaniel B. Palmer cruise NBP0103 in the Southern Ocean in 2001 (SOGLOBEC project) For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/2375
  • Dataset
    Particulate Organic Carbon and Nitrogen from RVIB Nathaniel B. Palmer cruises NBP0103, NBP0104, NBP0202, and NBP0204 in the Southern Ocean from 2001-2002 (SOGLOBEC project)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-05) Vernet, Maria
    Particulate Organic Carbon and Nitrogen from RVIB Nathaniel B. Palmer cruises NBP0103, NBP0104, NBP0202, and NBP0204 in the Southern Ocean from 2001-2002 (SOGLOBEC project) For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/2374
  • Dataset
    Chlorophyll data from bottles, buckets, and ice from RVIB Nathaniel B. Palmer cruises NBP0103, NBP0104, NBP0202, and NBP0204 in the Southern Ocean from 2001-2002 (SOGLOBEC project)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-04) Vernet, Maria
    Chlorophyll data from bottles, buckets, and ice from RVIB Nathaniel B. Palmer cruises NBP0103, NBP0104, NBP0202, and NBP0204 in the Southern Ocean from 2001-2002 (SOGLOBEC project) For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/2356
  • Article
    Export production and its regulating factors in the West Antarctica Peninsula region of the Southern Ocean
    (American Geophysical Union, 2012-04-24) Huang, Kuan ; Ducklow, Hugh W. ; Vernet, Maria ; Cassar, Nicolas ; Bender, Michael L.
    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.
  • Article
    Foehn winds link climate-driven warming to ice shelf evolution in Antarctica
    (John Wiley & Sons, 2015-11-03) Cape, Mattias R. ; Vernet, Maria ; Skvarca, Pedro ; Marinsek, Sebastian ; Scambos, Ted ; Domack, Eugene
    Rapid warming of the Antarctic Peninsula over the past several decades has led to extensive surface melting on its eastern side, and the disintegration of the Prince Gustav, Larsen A, and Larsen B ice shelves. The warming trend has been attributed to strengthening of circumpolar westerlies resulting from a positive trend in the Southern Annular Mode (SAM), which is thought to promote more frequent warm, dry, downsloping foehn winds along the lee, or eastern side, of the peninsula. We examined variability in foehn frequency and its relationship to temperature and patterns of synoptic-scale circulation using a multidecadal meteorological record from the Argentine station Matienzo, located between the Larsen A and B embayments. This record was further augmented with a network of six weather stations installed under the U.S. NSF LARsen Ice Shelf System, Antarctica, project. Significant warming was observed in all seasons at Matienzo, with the largest seasonal increase occurring in austral winter (+3.71°C between 1962–1972 and 1999–2010). Frequency and duration of foehn events were found to strongly influence regional temperature variability over hourly to seasonal time scales. Surface temperature and foehn winds were also sensitive to climate variability, with both variables exhibiting strong, positive correlations with the SAM index. Concomitant positive trends in foehn frequency, temperature, and SAM are present during austral summer, with sustained foehn events consistently associated with surface melting across the ice sheet and ice shelves. These observations support the notion that increased foehn frequency played a critical role in precipitating the collapse of the Larsen B ice shelf.
  • Dataset
    Simulated in situ production data from RVIB Nathaniel B. Palmer cruises NBP0103, NBP0104, NBP0202, and NBP0204 in the Southern Ocean from 2001-2002 (SOGLOBEC project)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-05) Vernet, Maria
    Simulated in situ production data from RVIB Nathaniel B. Palmer cruises NBP0103, NBP0104, NBP0202, and NBP0204 in the Southern Ocean from 2001-2002 (SOGLOBEC project) For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/2376
  • Dataset
    Integrated daily Photosynthetically Available Radiation (PAR) data from RVIB Nathaniel B. Palmer cruises NBP0103, NBP0104, NBP0202, and NBP0204 in the Southern Ocean from 2001-2002 (SOGLOBEC project)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-04) Vernet, Maria
    Integrated daily Photosynthetically Available Radiation (PAR) data from RVIB Nathaniel B. Palmer cruises NBP0103, NBP0104, NBP0202, and NBP0204 in the Southern Ocean from 2001-2002 (SOGLOBEC project) For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/2362
  • Article
    A new US polar research vessel for the twenty-first century
    (The Oceanography Society, 2012-09) Dunbar, Robert B. ; Alberts, Jon ; Ashjian, Carin J. ; Asper, Vernon L. ; Chayes, Dale ; Domack, Eugene ; Ducklow, Hugh W. ; Huber, Bruce ; Lawver, Lawrence ; Oliver, Daniel ; Russell, Doug ; Smith, Craig R. ; Vernet, Maria
    Scientific and political interests at the poles are significant and rapidly increasing, driven in part by the effects of climate change and emerging geopolitical realities. The polar regions provide important services to global ecosystems and humankind, ranging from food and energy to freshwater and biodiversity. Yet the poles are experiencing changes at rates that far outpace the rest of the planet. Coastal Arctic communities are impacted by climate change through coastal erosion, sea level rise, ice loss, and altered marine food webs, threatening the future of their subsistence lifestyle. Climate change has dramatically increased the melt rate of ice sheets and glaciers at both poles and has the potential to significantly raise sea level worldwide. Oil and gas drilling as well as transportation in the Arctic have reached all-time high levels, in part because of reduced sea ice cover. Tourism is a growing industry at both poles, bringing more than 20,000 tourists each year to the western Antarctic Peninsula alone. The collateral effects of human activities include the potential for pollution of the marine environment, particularly through spills of hydrocarbons. Our ability to understand the effects of such activities and mishaps is limited, particularly in ice-covered areas during winter.