Schlosser
Peter
Schlosser
Peter
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ArticleMantle 3He distribution and deep circulation in the Indian Ocean(American Geophysical Union, 2004-06-10) Srinivasan, Ashwanth ; Top, Zafer ; Schlosser, Peter ; Hohmann, Roland ; Iskandarani, Mohamed ; Olson, Donald B. ; Lupton, John E. ; Jenkins, William J.The World Ocean Circulation Experiment Indian Ocean helium isotope data are mapped and features of intermediate and deep circulation are inferred and discussed. The 3He added to the deep Indian Ocean originates from (1) a strong source on the mid-ocean ridge at about 19°S/65°E, (2) a source located in the Gulf of Aden in the northwestern Indian Ocean, (3) sources located in the convergent margins in the northeastern Indian Ocean, and (4) water imported from the Indonesian Seas. The main circulation features inferred from the 3He distribution include (1) deep (2000–3000 m) eastward flow in the central Indian Ocean, which overflows into the West Australian Basin through saddles in the Ninetyeast Ridge, (2) a deep (2000–3000 m) southwestward flow in the western Indian Ocean, and (3) influx of Banda Sea Intermediate Waters associated with the deep core (1000–1500 m) of the through flow from the Pacific Ocean. The large-scale 3He distribution is consonant with the known pathways of deep and bottom water circulation in the Indian Ocean.
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ArticleChanges in gross oxygen production, net oxygen production, and air-water gas exchange during seasonal ice melt in Whycocomagh Bay, a Canadian estuary in the Bras d'or Lake system(European Geosciences Union, 2019-09-05) Manning, Cara C. ; Stanley, Rachel H. R. ; Nicholson, David P. ; Loose, Brice ; Lovely, Ann ; Schlosser, Peter ; Hatcher, Bruce G.Sea ice is an important control on gas exchange and primary production in polar regions. We measured net oxygen production (NOP) and gross oxygen production (GOP) using near-continuous measurements of the O2∕Ar gas ratio and discrete measurements of the triple isotopic composition of O2, during the transition from ice-covered to ice-free conditions, in Whycocomagh Bay, an estuary in the Bras d'Or Lake system in Nova Scotia, Canada. The volumetric gross oxygen production was 5.4+2.8−1.6 mmol O2 m−3 d−1, similar at the beginning and end of the time series, and likely peaked at the end of the ice melt period. Net oxygen production displayed more temporal variability and the system was on average net autotrophic during ice melt and net heterotrophic following the ice melt. We performed the first field-based dual tracer release experiment in ice-covered water to quantify air–water gas exchange. The gas transfer velocity at >90 % ice cover was 6 % of the rate for nearly ice-free conditions. Published studies have shown a wide range of results for gas transfer velocity in the presence of ice, and this study indicates that gas transfer through ice is much slower than the rate of gas transfer through open water. The results also indicate that both primary producers and heterotrophs are active in Whycocomagh Bay during spring while it is covered in ice.
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ArticleSea ice and its effect on CO2 flux between the atmosphere and the Southern Ocean interior(American Geophysical Union, 2011-11-15) Loose, Brice ; Schlosser, PeterThe advance and retreat of sea ice produces seasonal convection and stratification, dampens surface waves and creates a separation between the ocean and atmosphere. These are all phenomena that can affect the air-sea gas transfer velocity (k660), and therefore it is not straightforward to determine how sea ice cover modulates air-sea flux. In this study we use field estimates k660 to examine how sea ice affects the net gas flux between the ocean and atmosphere. An inventory of salinity, 3He, and CFC-11 in the mixed layer is used to infer k660 during the drift of Ice Station Weddell in 1992. The average of k660 is 0.11 m d−1 across nearly 100% ice cover. In comparison, the only prior field estimates of k660 are disproportionately larger, with average values of 2.4 m d−1 across 90% sea ice cover, and 3.2 m d−1 across approximately 70% sea ice cover. We use these values to formulate two scenarios for the modulation of k660 by the fraction of sea ice cover in a 1-D transport model for the Southern Ocean seasonal ice zone. Results show the net CO2 flux through sea ice cover represents 14–46% of the net annual air-sea flux, depending on the relationship between sea ice cover and k660. The model also indicates that as much as 68% of net annual CO2 flux in the sea ice zone occurs in the springtime marginal ice zone, which demonstrates the need for accurate parameterizations of gas flux and primary productivity under partially ice-covered conditions.
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ArticleInfluence of rain on air-sea gas exchange : lessons from a model ocean(American Geophysical Union, 2004-07-01) Ho, David T. ; Zappa, Christopher J. ; McGillis, Wade R. ; Bliven, Larry F. ; Ward, Brian ; Dacey, John W. H. ; Schlosser, Peter ; Hendricks, Melissa B.Rain has been shown to significantly enhance the rate of air-water gas exchange in fresh water environments, and the mechanism behind this enhancement has been studied in laboratory experiments. In the ocean, the effects of rain are complicated by the potential influence of density stratification at the water surface. Since it is difficult to perform controlled rain-induced gas exchange experiments in the open ocean, an SF6 evasion experiment was conducted in the artificial ocean at Biosphere 2. The measurements show a rapid depletion of SF6 in the surface layer due to rain enhancement of air-sea gas exchange, and the gas transfer velocity was similar to that predicted from the relationship established from freshwater laboratory experiments. However, because vertical mixing is reduced by stratification, the overall gas flux is lower than that found during freshwater experiments. Physical measurements of various properties of the ocean during the rain events further elucidate the mechanisms behind the observed response. The findings suggest that short, intense rain events accelerate gas exchange in oceanic environments.
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ArticleEvidence of an active volcanic heat source beneath the Pine Island Glacier(Nature Publishing Group, 2018-06-22) Loose, Brice ; Naveira Garabato, Alberto C. ; Schlosser, Peter ; Jenkins, William J. ; Vaughan, David ; Heywood, Karen J.Tectonic landforms reveal that the West Antarctic Ice Sheet (WAIS) lies atop a major volcanic rift system. However, identifying subglacial volcanism is challenging. Here we show geochemical evidence of a volcanic heat source upstream of the fast-melting Pine Island Ice Shelf, documented by seawater helium isotope ratios at the front of the Ice Shelf cavity. The localization of mantle helium to glacial meltwater reveals that volcanic heat induces melt beneath the grounded glacier and feeds the subglacial hydrological network crossing the grounding line. The observed transport of mantle helium out of the Ice Shelf cavity indicates that volcanic heat is supplied to the grounded glacier at a rate of ~ 2500 ± 1700 MW, which is ca. half as large as the active Grimsvötn volcano on Iceland. Our finding of a substantial volcanic heat source beneath a major WAIS glacier highlights the need to understand subglacial volcanism, its hydrologic interaction with the marine margins, and its potential role in the future stability of the WAIS.
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ArticleA comprehensive global oceanic dataset of helium isotope and tritium measurements.(Copernicus Publications, 2019-04-05) Jenkins, William J. ; Doney, Scott C. ; Fendrock, Michaela ; Fine, Rana A. ; Gamo, Toshitaka ; Jean-Baptiste, Philippe ; Key, Robert M. ; Klein, Birgit ; Lupton, John E. ; Newton, Robert ; Rhein, Monika ; Roether, Wolfgang ; Sano, Yuji ; Schlitzer, Reiner ; Schlosser, Peter ; Swift, James H.Tritium and helium isotope data provide key information on ocean circulation, ventilation, and mixing, as well as the rates of biogeochemical processes and deep-ocean hydrothermal processes. We present here global oceanic datasets of tritium and helium isotope measurements made by numerous researchers and laboratories over a period exceeding 60 years. The dataset's DOI is https://doi.org/10.25921/c1sn-9631, and the data are available at https://www.nodc.noaa.gov/ocads/data/0176626.xml (last access: 15 March 2019) or alternately http://odv.awi.de/data/ocean/jenkins-tritium-helium-data-compilation/ (last access: 13 March 2019) and includes approximately 60 000 valid tritium measurements, 63 000 valid helium isotope determinations, 57 000 dissolved helium concentrations, and 34 000 dissolved neon concentrations. Some quality control has been applied in that questionable data have been flagged and clearly compromised data excluded entirely. Appropriate metadata have been included, including geographic location, date, and sample depth. When available, we include water temperature, salinity, and dissolved oxygen. Data quality flags and data originator information (including methodology) are also included. This paper provides an introduction to the dataset along with some discussion of its broader qualities and graphics.
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ArticleThe transpolar drift as a source of riverine and shelf-derived trace elements to the central Arctic Ocean(American Geophysical Union, 2020-04-08) Charette, Matthew A. ; Kipp, Lauren ; Jensen, Laramie T. ; Dabrowski, Jessica S. ; Whitmore, Laura M. ; Fitzsimmons, Jessica N. ; Williford, Tatiana ; Ulfsbo, Adam ; Jones, Elizabeth M. ; Bundy, Randelle M. ; Vivancos, Sebastian M. ; Pahnke, Katharina ; John, Seth G. ; Xiang, Yang ; Hatta, Mariko ; Petrova, Mariia V. ; Heimbürger, Lars-Eric ; Bauch, Dorothea ; Newton, Robert ; Pasqualini, Angelica ; Agather, Alison ; Amon, Rainer M. W. ; Anderson, Robert F. ; Andersson, Per S. ; Benner, Ronald ; Bowman, Katlin ; Edwards, R. Lawrence ; Gdaniec, Sandra ; Gerringa, Loes J. A. ; González, Aridane G. ; Granskog, Mats A. ; Haley, Brian ; Hammerschmidt, Chad R. ; Hansell, Dennis A. ; Henderson, Paul B. ; Kadko, David C. ; Kaiser, Karl ; Laan, Patrick ; Lam, Phoebe J. ; Lamborg, Carl H. ; Levier, Martin ; Li, Xianglei ; Margolin, Andrew R. ; Measures, Christopher I. ; Middag, Rob ; Millero, Frank J. ; Moore, Willard S. ; Paffrath, Ronja ; Planquette, Helene ; Rabe, Benjamin ; Reader, Heather ; Rember, Robert ; Rijkenberg, Micha J. A. ; Roy-Barman, Matthieu ; van der Loeff, Michiel Rutgers ; Saito, Mak A. ; Schauer, Ursula ; Schlosser, Peter ; Sherrell, Robert M. ; Shiller, Alan M. ; Slagter, Hans ; Sonke, Jeroen E. ; Stedmon, Colin ; Woosley, Ryan J. ; Valk, Ole ; van Ooijen, Jan ; Zhang, RuifengA major surface circulation feature of the Arctic Ocean is the Transpolar Drift (TPD), a current that transports river‐influenced shelf water from the Laptev and East Siberian Seas toward the center of the basin and Fram Strait. In 2015, the international GEOTRACES program included a high‐resolution pan‐Arctic survey of carbon, nutrients, and a suite of trace elements and isotopes (TEIs). The cruises bisected the TPD at two locations in the central basin, which were defined by maxima in meteoric water and dissolved organic carbon concentrations that spanned 600 km horizontally and ~25–50 m vertically. Dissolved TEIs such as Fe, Co, Ni, Cu, Hg, Nd, and Th, which are generally particle‐reactive but can be complexed by organic matter, were observed at concentrations much higher than expected for the open ocean setting. Other trace element concentrations such as Al, V, Ga, and Pb were lower than expected due to scavenging over the productive East Siberian and Laptev shelf seas. Using a combination of radionuclide tracers and ice drift modeling, the transport rate for the core of the TPD was estimated at 0.9 ± 0.4 Sv (106 m3 s−1). This rate was used to derive the mass flux for TEIs that were enriched in the TPD, revealing the importance of lateral transport in supplying materials beneath the ice to the central Arctic Ocean and potentially to the North Atlantic Ocean via Fram Strait. Continued intensification of the Arctic hydrologic cycle and permafrost degradation will likely lead to an increase in the flux of TEIs into the Arctic Ocean.