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van der Mheen M, Wernberg T, Pattiaratchi C, Pessarrodona A, Janekovic I, Simpkins T, Hovey R, Filbee-Dexter K. Substantial kelp detritus exported beyond the continental shelf by dense shelf water transport. Sci Rep 2024; 14:839. [PMID: 38191572 PMCID: PMC10774291 DOI: 10.1038/s41598-023-51003-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 12/29/2023] [Indexed: 01/10/2024] Open
Abstract
Kelp forests may contribute substantially to ocean carbon sequestration, mainly through transporting kelp carbon away from the coast and into the deep sea. However, it is not clear if and how kelp detritus is transported across the continental shelf. Dense shelf water transport (DSWT) is associated with offshore flows along the seabed and provides an effective mechanism for cross-shelf transport. In this study, we determine how effective DSWT is in exporting kelp detritus beyond the continental shelf edge, by considering the transport of simulated sinking kelp detritus from a region of Australia's Great Southern Reef. We show that DSWT is the main mechanism that transports simulated kelp detritus past the continental shelf edge, and that export is negligible when DSWT does not occur. We find that 51% per year of simulated kelp detritus is transported past the continental shelf edge, or 17-29% when accounting for decomposition while in transit across the shelf. This is substantially more than initial global estimates. Because DSWT occurs in many mid-latitude locations around the world, where kelp forests are also most productive, export of kelp carbon from the coast could be considerably larger than initially expected.
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Affiliation(s)
- Mirjam van der Mheen
- School of Biological Sciences and UWA Oceans Institute, University of Western Australia, Perth, WA, Australia.
| | - Thomas Wernberg
- School of Biological Sciences and UWA Oceans Institute, University of Western Australia, Perth, WA, Australia
- Institute of Marine Research, Nye Flødevigveien 20, His, 4817, Norway
| | - Charitha Pattiaratchi
- Oceans Graduate School and UWA Oceans Institute, University of Western Australia, Perth, WA, Australia
| | - Albert Pessarrodona
- School of Biological Sciences and UWA Oceans Institute, University of Western Australia, Perth, WA, Australia
| | - Ivica Janekovic
- Oceans Graduate School and UWA Oceans Institute, University of Western Australia, Perth, WA, Australia
| | - Taylor Simpkins
- School of Biological Sciences and UWA Oceans Institute, University of Western Australia, Perth, WA, Australia
| | - Renae Hovey
- School of Biological Sciences and UWA Oceans Institute, University of Western Australia, Perth, WA, Australia
| | - Karen Filbee-Dexter
- School of Biological Sciences and UWA Oceans Institute, University of Western Australia, Perth, WA, Australia
- Institute of Marine Research, Nye Flødevigveien 20, His, 4817, Norway
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Vickers ML, Lengger SK, Bernasconi SM, Thibault N, Schultz BP, Fernandez A, Ullmann CV, McCormack P, Bjerrum CJ, Rasmussen JA, Hougård IW, Korte C. Cold spells in the Nordic Seas during the early Eocene Greenhouse. Nat Commun 2020; 11:4713. [PMID: 32948769 PMCID: PMC7501286 DOI: 10.1038/s41467-020-18558-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 08/21/2020] [Indexed: 11/18/2022] Open
Abstract
The early Eocene (c. 56 - 48 million years ago) experienced some of the highest global temperatures in Earth’s history since the Mesozoic, with no polar ice. Reports of contradictory ice-rafted erratics and cold water glendonites in the higher latitudes have been largely dismissed due to ambiguity of the significance of these purported cold-climate indicators. Here we apply clumped isotope paleothermometry to a traditionally qualitative abiotic proxy, glendonite calcite, to generate quantitative temperature estimates for northern mid-latitude bottom waters. Our data show that the glendonites of the Danish Basin formed in waters below 5 °C, at water depths of <300 m. Such near-freezing temperatures have not previously been reconstructed from proxy data for anywhere on the early Eocene Earth, and these data therefore suggest that regionalised cool episodes punctuated the background warmth of the early Eocene, likely linked to eruptive phases of the North Atlantic Igneous Province. The early Eocene was characterized by exceptionally high global temperatures and no polar ice. Here, clumped isotope paleothermometry of glendonite calcite from the Danish Basin shows that these were formed in waters below 5 °C, indicating that regionalised cool episodes punctuated the background warmth of the early Eocene.
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Affiliation(s)
- Madeleine L Vickers
- IGN, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen, Denmark.
| | - Sabine K Lengger
- Biogeochemistry Research Centre, School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, UK
| | | | - Nicolas Thibault
- IGN, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen, Denmark
| | | | - Alvaro Fernandez
- Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Allégaten 41, N-5007, Bergen, Norway
| | - Clemens V Ullmann
- Camborne School of Mines, University of Exeter, Penryn Campus, Penryn, Cornwall, TR10 9FE, UK
| | - Paul McCormack
- Biogeochemistry Research Centre, School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus, Plymouth, PL4 8AA, UK
| | - Christian J Bjerrum
- IGN, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen, Denmark
| | - Jan Audun Rasmussen
- Museum Mors, Fossil- and Mo-clay Museum, Skarrehagevej 8, 7900, Nykøbing Mors, Denmark
| | | | - Christoph Korte
- IGN, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen, Denmark
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Occurrence and seasonal variability of Dense Shelf Water Cascades along Australian continental shelves. Sci Rep 2020; 10:9732. [PMID: 32546836 PMCID: PMC7298046 DOI: 10.1038/s41598-020-66711-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 05/21/2020] [Indexed: 11/21/2022] Open
Abstract
Transport of water between the coast and the deeper ocean, across the continental shelf, is an important process for the distribution of biota, nutrients, suspended and dissolved material on the shelf. Presence of denser water on the inner continental shelf results in a cross-shelf density gradient that drives a gravitational circulation with offshore transport of denser water along the sea bed that is defined as Dense Shelf Water Cascade (DSWC). Analysis of field data, collected from multiple ocean glider data missions around Australia, confirmed that under a range of wind and tidal conditions, DSWC was a regular occurrence during autumn and winter months over a coastline spanning > 10,000 km. It is shown that even in the presence of relatively high wind- and tidal-induced vertical mixing, DSWCs were present due to the strength of the cross-shelf density gradient. The occurrence of DSWC around Australia is unique with continental scale forcing through air-sea fluxes that overcome local wind and tidal forcing. It is shown that DSWC acts as a conduit to transport suspended material across the continental shelf and is a critical process that influences water quality on the inner continental shelf.
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Spatial and Temporal Variability of Dense Shelf Water Cascades along the Rottnest Continental Shelf in Southwest Australia. JOURNAL OF MARINE SCIENCE AND ENGINEERING 2019. [DOI: 10.3390/jmse7020030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Along the majority of Australian shallow coastal regions, summer evaporation increases the salinity of shallow waters, and subsequently in autumn/winter, the nearshore waters become cooler due to heat loss. This results in the formation of horizontal density gradients with density increasing toward the coast that generates gravity currents known as dense shelf water cascades (DSWCs) flowing offshore along the sea bed. DSWCs play important role in ecological and biogeochemical processes in Australian waters through the transport of dissolved and suspended materials offshore. In this study a numerical ocean circulation model of Rottnest continental shelf, validated using simultaneous ocean glider and mooring data, indicated that the passage of cold fronts associated with winter storms resulted in rapid heat loss through evaporative cooling. These conditions resulted in enhancement of the DSWCs due to modifications of the cross-shelf density gradient and wind effects. Specifically, onshore (offshore) directed winds resulted in an enhancement (inhibition) of DSWCs due to downwelling (vertical mixing). Consequently, the largest DSWC events occurred during the cold fronts when atmospheric temperatures reinforced density gradients and onshore winds promoted downwelling that enhanced DSWCs. Advection of DSWCs was also strongly influenced by the wind conditions, with significantly more transport occurring along-shelf compared to cross-shelf.
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Bernardi Aubry F, Falcieri FM, Chiggiato J, Boldrin A, Luna GM, Finotto S, Camatti E, Acri F, Sclavo M, Carniel S, Bongiorni L. Massive shelf dense water flow influences plankton community structure and particle transport over long distance. Sci Rep 2018. [PMID: 29540707 PMCID: PMC5852251 DOI: 10.1038/s41598-018-22569-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Dense waters (DW) formation in shelf areas and their cascading off the shelf break play a major role in ventilating deep waters, thus potentially affecting ecosystem functioning and biogeochemical cycles. However, whether DW flow across shelves may affect the composition and structure of plankton communities down to the seafloor and the particles transport over long distances has not been fully investigated. Following the 2012 north Adriatic Sea cold outbreak, DW masses were intercepted at ca. 460 km south the area of origin and compared to resident ones in term of plankton biomass partitioning (pico to micro size) and phytoplankton species composition. Results indicated a relatively higher contribution of heterotrophs in DW than in deep resident water masses, probably as result of DW-mediated advection of fresh organic matter available to consumers. DWs showed unusual high abundances of Skeletonema sp., a diatom that bloomed in the north Adriatic during DW formation. The Lagrangian numerical model set up on this diatom confirmed that DW flow could be an important mechanism for plankton/particles export to deep waters. We conclude that the predicted climate-induced variability in DW formation events could have the potential to affect the ecosystem functioning of the deeper part of the Mediterranean basin, even at significant distance from generation sites.
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Affiliation(s)
- Fabrizio Bernardi Aubry
- Institute of Marine Sciences, National Research Council, Arsenale - Tesa 104, Castello 2737/F, 30122, Venice, Italy
| | - Francesco Marcello Falcieri
- Institute of Marine Sciences, National Research Council, Arsenale - Tesa 104, Castello 2737/F, 30122, Venice, Italy
| | - Jacopo Chiggiato
- Institute of Marine Sciences, National Research Council, Arsenale - Tesa 104, Castello 2737/F, 30122, Venice, Italy
| | - Alfredo Boldrin
- Institute of Marine Sciences, National Research Council, Arsenale - Tesa 104, Castello 2737/F, 30122, Venice, Italy
| | - Gian Marco Luna
- Institute of Marine Sciences, National Research Council, Largo Fiera della Pesca 2, 60125, Ancona, Italy
| | - Stefania Finotto
- Institute of Marine Sciences, National Research Council, Arsenale - Tesa 104, Castello 2737/F, 30122, Venice, Italy
| | - Elisa Camatti
- Institute of Marine Sciences, National Research Council, Arsenale - Tesa 104, Castello 2737/F, 30122, Venice, Italy
| | - Francesco Acri
- Institute of Marine Sciences, National Research Council, Arsenale - Tesa 104, Castello 2737/F, 30122, Venice, Italy
| | - Mauro Sclavo
- Institute of Marine Sciences, National Research Council, Arsenale - Tesa 104, Castello 2737/F, 30122, Venice, Italy
| | - Sandro Carniel
- Institute of Marine Sciences, National Research Council, Arsenale - Tesa 104, Castello 2737/F, 30122, Venice, Italy
| | - Lucia Bongiorni
- Institute of Marine Sciences, National Research Council, Arsenale - Tesa 104, Castello 2737/F, 30122, Venice, Italy.
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Luna GM, Chiggiato J, Quero GM, Schroeder K, Bongiorni L, Kalenitchenko D, Galand PE. Dense water plumes modulate richness and productivity of deep sea microbes. Environ Microbiol 2016; 18:4537-4548. [DOI: 10.1111/1462-2920.13510] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 08/19/2016] [Indexed: 11/27/2022]
Affiliation(s)
- Gian Marco Luna
- Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR-ISMAR); Ancona Italy
| | - Jacopo Chiggiato
- Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR-ISMAR); Venezia Italy
| | - Grazia Marina Quero
- Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR-ISMAR); Venezia Italy
| | - Katrin Schroeder
- Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR-ISMAR); Venezia Italy
| | - Lucia Bongiorni
- Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine (CNR-ISMAR); Venezia Italy
| | - Dimitri Kalenitchenko
- Sorbonne Universités, UPMC Université Paris 06, CNRS, Laboratoire d'Ecogeochimie des Environnements Benthiques (LECOB), Observatoire Océanologique; Banyuls sur Mer France
| | - Pierre E. Galand
- Sorbonne Universités, UPMC Université Paris 06, CNRS, Laboratoire d'Ecogeochimie des Environnements Benthiques (LECOB), Observatoire Océanologique; Banyuls sur Mer France
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Han D, Nam SI, Ha HK, Kim H, Sadowsky MJ, Lee YK, Hur HG. Bacterial biogeography influenced by shelf-basin exchange in the Arctic surface sediment at the Chukchi Borderland. Environ Microbiol 2015; 18:668-78. [PMID: 26411339 DOI: 10.1111/1462-2920.13064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 09/18/2015] [Accepted: 09/20/2015] [Indexed: 11/28/2022]
Abstract
It has been known that continental shelves around the Arctic Ocean play a major role in the ventilation of the deep basins as a consequence of shelf-basin exchange. In the present study, we found that bacterial assemblage of the surface sediment was different from that of seawater while seawater harboured local bacterial assemblages in response to the Arctic hydrography. This finding suggests that the Arctic seafloor sediments may have distinctive bacterial biogeography. Moreover, the distribution of bacterial assemblages and physicochemical properties in surface sediments changed gradually from the Arctic continental shelf to deep-sea basin. Based on the results, bacterial biogeography in the Arctic seafloor sediments may be influenced by winnowing and re-deposition of surface sediments through the sediment gravity flow. The present study offers a deeper understanding of shelf convection and its role for the construction of bacterial assemblages in the Arctic Ocean.
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Affiliation(s)
- Dukki Han
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, Republic of Korea
| | - Seung-Il Nam
- Korea Polar Research Institute, Incheon, 21990, Republic of Korea
| | - Ho Kyung Ha
- Department of Ocean Sciences, Inha University, Incheon, 22212, Republic of Korea
| | - Hyoungjun Kim
- Korea Polar Research Institute, Incheon, 21990, Republic of Korea
| | - Michael J Sadowsky
- Department of Soil, Water, and Climate, Biotechnology Institute, Microbial Plant and Genomics Institute, University of Minnesota, St. Paul, MN, 55108, USA
| | - Yoo Kyung Lee
- Korea Polar Research Institute, Incheon, 21990, Republic of Korea
| | - Hor-Gil Hur
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, 61005, Republic of Korea
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Ivanov V, Watanabe E. Does Arctic sea ice reduction foster shelf-basin exchange? ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2013; 23:1765-1777. [PMID: 24555308 DOI: 10.1890/11-1069.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The recent shift in Arctic ice conditions from prevailing multi-year ice to first-year ice will presumably intensify fall-winter sea ice freezing and the associated salt flux to the underlying water column. Here, we conduct a dual modeling study whose results suggest that the predicted catastrophic consequences for the global thermohaline circulation (THC), as a result of the disappearance of Arctic sea ice, may not necessarily occur. In a warmer climate, the substantial fraction of dense water feeding the Greenland-Scotland overflow may form on Arctic shelves and cascade to the deep basin, thus replenishing dense water, which currently forms through open ocean convection in the sub-Arctic seas. We have used a simplified model for estimating how increased ice production influences shelf-basin exchange associated with dense water cascading. We have carried out case studies in two regions of the Arctic Ocean where cascading was observed in the past. The baseline range of buoyancy-forcing derived from the columnar ice formation was calculated as part of a 30-year experiment of the pan-Arctic coupled ice-ocean general circulation model (GCM). The GCM results indicate that mechanical sea ice divergence associated with lateral advection accounts for a significant part of the interannual variations in sea ice thermal production in the coastal polynya regions. This forcing was then rectified by taking into account sub-grid processes and used in a regional model with analytically prescribed bottom topography and vertical stratification in order to examine specific cascading conditions in the Pacific and Atlantic sectors of the Arctic Ocean. Our results demonstrate that the consequences of enhanced ice formation depend on geographical location and shelf-basin bathymetry. In the Pacific sector, strong density stratification in slope waters impedes noticeable deepening of shelf-origin water, even for the strongest forcing applied. In the Atlantic sector, a 1.5x increase of salt flux leads to a threefold increase of shelf-slope volume flux below the warm core of Atlantic water. This threefold increase would be a sufficient substitute for a similar amount of dense water that currently forms in the Greenland, Iceland, and Norwegian (GIN) seas but is expected to decrease in a warming climate.
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Affiliation(s)
- Vladimir Ivanov
- International Arctic Research Center, University of Alaska, Fairbanks, Alaska 99775, USA.
| | - Eiji Watanabe
- International Arctic Research Center, University of Alaska, Fairbanks, Alaska 99775, USA
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Skogseth R, Smedsrud LH, Nilsen F, Fer I. Observations of hydrography and downflow of brine-enriched shelf water in the Storfjorden polynya, Svalbard. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007jc004452] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Rosentraub Z, Brenner S. Circulation over the southeastern continental shelf and slope of the Mediterranean Sea: Direct current measurements, winds, and numerical model simulations. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jc003775] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ivanov VV, Golovin PN. Observations and modeling of dense water cascading from the northwestern Laptev Sea shelf. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jc003882] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Canals M, Puig P, de Madron XD, Heussner S, Palanques A, Fabres J. Flushing submarine canyons. Nature 2006; 444:354-7. [PMID: 17108962 DOI: 10.1038/nature05271] [Citation(s) in RCA: 612] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Accepted: 09/13/2006] [Indexed: 11/09/2022]
Abstract
The continental slope is a steep, narrow fringe separating the coastal zone from the deep ocean. During low sea-level stands, slides and dense, sediment-laden flows erode the outer continental shelf and the continental slope, leading to the formation of submarine canyons that funnel large volumes of sediment and organic matter from shallow regions to the deep ocean(1). During high sea-level stands, such as at present, these canyons still experience occasional sediment gravity flows(2-5), which are usually thought to be triggered by sediment failure or river flooding. Here we present observations from a submarine canyon on the Gulf of Lions margin, in the northwest Mediterranean Sea, that demonstrate that these flows can also be triggered by dense shelf water cascading (DSWC)-a type of current that is driven solely by seawater density contrast. Our results show that DSWC can transport large amounts of water and sediment, reshape submarine canyon floors and rapidly affect the deep-sea environment. This cascading is seasonal, resulting from the formation of dense water by cooling and/or evaporation, and occurs on both high- and low-latitude continental margins(6-8). DSWC may therefore transport large amounts of sediment and organic matter to the deep ocean. Furthermore, changes in the frequency and intensity of DSWC driven by future climate change may have a significant impact on the supply of organic matter to deep-sea ecosystems and on the amount of carbon stored on continental margins and in ocean basins.
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Affiliation(s)
- Miquel Canals
- CRG Marine Geosciences, Department of Stratigraphy, Paleontology and Marine Geosciences, University of Barcelona, E-08028 Barcelona, Spain.
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Skogseth R, Fer I, Haugan PM. Dense-water production and overflow from an arctic coastal polynya in Storfjorden. THE NORDIC SEAS: AN INTEGRATED PERSPECTIVE OCEANOGRAPHY, CLIMATOLOGY, BIOGEOCHEMISTRY, AND MODELING 2005. [DOI: 10.1029/158gm07] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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