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  • AGU (American Geophysical Union)  (12)
  • Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung  (8)
  • 2015-2019  (20)
  • 1
    Publication Date: 2022-01-31
    Description: Gelatinous zooplankton (Cnidaria, Ctenophora, and Urochordata, namely, Thaliacea) are ubiquitous members of plankton communities linking primary production to higher trophic levels and the deep ocean by serving as food and transferring “jelly‐carbon” (jelly‐C) upon bloom collapse. Global biomass within the upper 200 m reaches 0.038 Pg C, which, with a 2–12 months life span, serves as the lower limit for annual jelly‐C production. Using over 90,000 data points from 1934 to 2011 from the Jellyfish Database Initiative as an indication of global biomass (JeDI: http://jedi.nceas.ucsb.edu, http://www.bco‐dmo.org/dataset/526852), upper ocean jelly‐C biomass and production estimates, organism vertical migration, jelly‐C sinking rates, and water column temperature profiles from GLODAPv2, we quantitatively estimate jelly‐C transfer efficiency based on Longhurst Provinces. From the upper 200 m production estimate of 0.038 Pg C year−1, 59–72% reaches 500 m, 46–54% reaches 1,000 m, 43–48% reaches 2,000 m, 32–40% reaches 3,000 m, and 25–33% reaches 4,500 m. This translates into ~0.03, 0.02, 0.01, and 0.01 Pg C year−1, transferred down to 500, 1,000, 2,000, and 4,500 m, respectively. Jelly‐C fluxes and transfer efficiencies can occasionally exceed phytodetrital‐based sediment trap estimates in localized open ocean and continental shelves areas under large gelatinous blooms or jelly‐C mass deposition events, but this remains ephemeral and transient in nature. This transfer of fast and permanently exported carbon reaching the ocean interior via jelly‐C constitutes an important component of the global biological soft‐tissue pump, and should be addressed in ocean biogeochemical models, in particular, at the local and regional scale.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 2
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    Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung
    In:  EPIC3Communications and Media Relations, Bremerhaven, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 2 p.
    Publication Date: 2022-04-05
    Repository Name: EPIC Alfred Wegener Institut
    Type: Outreach , notRev
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  • 3
    Publication Date: 2022-03-09
    Description: The seasonal and interannual variability of chlorophyll in the Gulf of Mexico open waters is studied using a three‐dimensional coupled physical‐biogeochemical model. A 5 years hindcast driven by realistic open‐boundary conditions, atmospheric forcings, and freshwater discharges from rivers is performed. The use of recent in situ observations allowed an in‐depth evaluation of the model nutrient and chlorophyll seasonal distributions, including the chlorophyll vertical structure. We find that different chlorophyll patterns of temporal variability coexist in the deep basin which thereby cannot be considered as a homogeneous region with respect to chlorophyll dynamics. A partitioning of the Gulf of Mexico open waters based on the winter chlorophyll concentration increase is then proposed. This partition is basically explained by the amount of nutrients injected into the euphotic layer which is highly constrained by the dynamic of the winter mixed layer. The seasonal and interannual variability appears to be affected by the variability of atmospheric fluxes and mesoscale dynamics (Loop Current eddies in particular). Finally, estimates of primary production in the deep basin are provided.
    Type: Article , PeerReviewed
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  • 4
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    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Solid Earth, 121 (3). pp. 1405-1424.
    Publication Date: 2019-09-23
    Description: A bottom-simulating reflector (BSR) occurs west of Svalbard in water depths exceeding 600 m, indicating that gas hydrate occurrence in marine sediments is more widespread in this region than anywhere else on the eastern North Atlantic margin. Regional BSR mapping shows the presence of hydrate and free gas in several areas, with the largest area located north of the Knipovich Ridge, a slow-spreading ridge segment of the Mid Atlantic Ridge system. Here, heat flow is high (up to 330 mW m-2), increasing towards the ridge axis. The coinciding maxima in across-margin BSR width and heat flow suggest that the Knipovich Ridge influenced methane generation in this area. This is supported by recent finds of thermogenic methane at cold seeps north of the ridge termination. To evaluate the source rock potential on the western Svalbard margin, we applied 1D petroleum system modeling at three sites. The modeling shows that temperature and burial conditions near the ridge were sufficient to produce hydrocarbons. The bulk petroleum mass produced since the Eocene is at least 5 kt and could be as high as ~0.2 Mt. Most likely, source rocks are Miocene organic-rich sediments and a potential Eocene source rock that may exist in the area if early rifting created sufficiently deep depocenters. Thermogenic methane production could thus explain the more widespread presence of gas hydrates north of the Knipovich Ridge. The presence of microbial methane on the upper continental slope and shelf indicates that the origin of methane on the Svalbard margin varies spatially.
    Type: Article , PeerReviewed
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  • 5
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    Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung
    In:  EPIC3Communications and Media Relations, Bremerhaven, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 17 p.
    Publication Date: 2019-02-13
    Repository Name: EPIC Alfred Wegener Institut
    Type: Outreach , notRev
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  • 6
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    Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung
    In:  EPIC3Communications and Media Relations, Bremerhaven, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 17 p.
    Publication Date: 2016-06-14
    Repository Name: EPIC Alfred Wegener Institut
    Type: Outreach , notRev
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  • 7
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    Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung
    In:  EPIC3Communications and Media Relations, Bremerhaven, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 17 p.
    Publication Date: 2017-07-25
    Repository Name: EPIC Alfred Wegener Institut
    Type: Outreach , notRev
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  • 8
    Publication Date: 2023-03-09
    Description: The Weddell Gyre (WG) is one of the main oceanographic features of the Southern Ocean south of the Antarctic Circumpolar Current which plays an influential role in global ocean circulation as well as gas exchange with the atmosphere. We review the state‐of‐the art knowledge concerning the WG from an interdisciplinary perspective, uncovering critical aspects needed to understand this system's role in shaping the future evolution of oceanic heat and carbon uptake over the next decades. The main limitations in our knowledge are related to the conditions in this extreme and remote environment, where the polar night, very low air temperatures, and presence of sea ice year‐round hamper field and remotely sensed measurements. We highlight the importance of winter and under‐ice conditions in the southern WG, the role that new technology will play to overcome present‐day sampling limitations, the importance of the WG connectivity to the low‐latitude oceans and atmosphere, and the expected intensification of the WG circulation as the westerly winds intensify. Greater international cooperation is needed to define key sampling locations that can be visited by any research vessel in the region. Existing transects sampled since the 1980s along the Prime Meridian and along an East‐West section at ~62°S should be maintained with regularity to provide answers to the relevant questions. This approach will provide long‐term data to determine trends and will improve representation of processes for regional, Antarctic‐wide, and global modeling efforts—thereby enhancing predictions of the WG in global ocean circulation and climate.
    Type: Article , PeerReviewed
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  • 9
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    AGU (American Geophysical Union) | Wiley
    In:  Earth's Future, 5 (12). pp. 1252-1266.
    Publication Date: 2020-11-23
    Description: The potential of Coastal Ocean Alkalinization (COA), a carbon dioxide removal (CDR) climate engineering strategy that chemically increases ocean carbon uptake and storage, is investigated with an Earth system model of intermediate complexity. The CDR potential and possible environmental side effects are estimated for various COA deployment scenarios, assuming olivine as the alkalinity source in ice-free coastal waters (about 8.6% of the global ocean's surface area), with dissolution rates being a function of grain size, ambient seawater temperature and pH. Our results indicate that for a large-enough olivine deployment of small-enough grain sizes (10 μm), atmospheric CO2 could be reduced by more than 800 GtC by the year 2100. However, COA with coarse olivine grains (1000 μm) has little CO2 sequestration potential on this time scale. Ambitious CDR with fine olivine grains would increase coastal aragonite saturation Ω to levels well beyond those that are currently observed. When imposing upper limits for aragonite saturation levels (Ωlim) in the grid boxes subject to COA (Ωlim = 3.4 and 9 chosen as examples), COA still has the potential to reduce atmospheric CO2 by 265 GtC (Ωlim=3.4) to 790 GtC (Ωlim=9) and increase ocean carbon storage by 290 Gt (Ωlim=3.4) to 913 Gt (Ωlim=9) by year 2100.
    Type: Article , PeerReviewed
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  • 10
    Publication Date: 2022-01-31
    Description: Prediction and Research Moored Array in the Tropical Atlantic (PIRATA) is a multinational program initiated in 1997 in the tropical Atlantic to improve our understanding and ability to predict ocean-atmosphere variability. PIRATA consists of a network of moored buoys providing meteorological and oceanographic data transmitted in real time to address fundamental scientific questions as well as societal needs. The network is maintained through dedicated yearly cruises, which allow for extensive complementary shipboard measurements and provide platforms for deployment of other components of the Tropical Atlantic Observing System. This paper describes network enhancements, scientific accomplishments and successes obtained from the last 10 years of observations, and additional results enabled by cooperation with other national and international programs. Capacity building activities and the role of PIRATA in a future Tropical Atlantic Observing System that is presently being optimized are also described.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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