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  • 1
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    Pergamon Press
    In:  Deep Sea Research Part A: Oceanographic Research Papers, 35 (12). pp. 1919-1935.
    Publikationsdatum: 2020-08-04
    Beschreibung: Helium data from the waters of the Bransfield Strait, the southern Drake Passage and the northwestern shelf of the Weddell Sea are presented. The 3He profiles from the eastern and central basins of the Bransfield Strait show maxima (δ3He ≈ 7%) below the sill depths that separate the strait from the surrounding open ocean. The 3He excess is interpreted as a local injection of a 3He-rich helium component into the deep waters of the Bransfield Strait from backarc rifting. Tritiogenic 3He and excess 3He from mixing with Circumpolar Deep Water are excluded as possible sources. The estimated 3He/4He ratio of the injected helium component (2.4–5.0 × 10−6) is less than that of pure mantle helium and may contain radiogenic helium from continental crustal material which underlies the Bransfield Strait.
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  • 2
    Publikationsdatum: 2020-06-05
    Beschreibung: Data from sections across the Eurasian Basin of the Arctic Ocean occupied in 1987 and 1991 are used to derive information on the freshwater balance of the Arctic Ocean and on sources of the deep waters of the Nansen, Amundsen and Makarov basins. Using salinity, H218O, and mass balances we estimate the river-runoff and the sea-ice melt water fractions contained in the upper waters of the Arctic Ocean and infer pathways of the river-runoff signal from the shelf seas across the central Arctic Ocean to Fram Strait. The average mean residence time of the river-runoff fraction contained in the Arctic Ocean halocline is determined to be about 11 to 14 years. Pacific water entering through Bering Strait is traced using silicate and its influence on the halocline waters of the Canadian Basin is estimated. Water column inventories of river-runoff and sea-ice melt water are calculated for a section just north of Fram Strait and implications of these inventories for sea-ice export through Fram Strait are discussed. Comparison of the ratios of shelf water, Atlantic water and the deep waters of the Arctic Ocean indicate that the sources of the deep and bottom waters of the Eurasian Basin are located in the Barents and Kara seas.
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  • 3
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    AMS (American Meteorological Society)
    In:  Journal of Physical Oceanography, 16 (5). pp. 814-826.
    Publikationsdatum: 2018-04-04
    Beschreibung: Simulated transient-tracer distributions (tritium, 3H3, freons) on the isopycnal horizons σ0=26.5 and 26.8 kg m−3 are presented for the East Atlantic, 10° −40°N. Tracer transport is modeled by employing a baroclinic flow field based on empirical data in a kinematic isopycnal advection-diffusion numerical model, in which winter convection is taken as the mechanism of communication with the ocean surface layer, and the isopycnal diffusivity is a free parameter. Diapucnic transport is ignored. The simulations employ time-dependent tracer boundary conditions, which are constructed on the basis of available observations. Simulations are compared to data obtained on a meridional section in 1981 (F/S Meteor, cruise 56/5). Best simulations were obtained by means of a subjective optimization procedure. On both levels, the observed distributions and the best simulated distributions agree well. The fact that the surface boundary conditions and interior distributions of the tracers are distinctly different leads us to the conclusion that our model provides a consistent description of upper main-thermocline ventilation and interior transport Surface-water densities in February are found to represent adequately the winter outcrop boundaries with an uncertainty of about ±300 km across. The required isopycnal diffusivity south of 29°N is 1700 m2 s−1, and 2900 m2 s−1 further north (+70/−40%). Interior transport is found to be predominantly advective. Advective ventilation across 30.5°N east of 33°W amounts to only 12% and 40% for the 26.5 and 26.8 horizons of the total ventilation rates reported by Sarmiento. The North Atlantic/South Atlantic Central Water boundary near 15°N is found to be predominantly determined by advection.
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  • 4
    Publikationsdatum: 2020-06-04
    Beschreibung: A technique for 14C measurement of small volume (0.5L) oceanic water samples by Accelerator Mass Spectrometry (AMS) is described. Samples were taken from a CTD/rosette system used for standard hydrographic work. After CO2 extraction and target preparation, the samples were measured at the Zürich tandem accelerator facility. On the basis of 14C data from samples collected on a station in the northern Weddell Sea, the precision of the measurements is estimated to ca ±8‰. The error in the present AMS results is dominated by the statistical error in 14C detection. From results of duplicate targets, it is concluded that a precision of ±5° can be reached. The 14C data are discussed in relation to the Weddell Sea hydrography.
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  • 5
    Publikationsdatum: 2017-03-09
    Beschreibung: We present ΔA14C and 39Ar data collected in the Nansen, Amundsen and Makarov basins during two expeditions to the central Arctic Ocean (RV Polarstern cruises ARK IV/3, 1987 and ARK VIII/3, 1991). The data are used, together with published Δ14C values, to describe the distribution of Δ14C in all major basins of the Arctic Ocean (Nansen, Amundsen, Makarov and Canada Basins), as well as the 39Ar distribution in the Nansen Basin and the deep waters of the Amundsen and Makarov Basins. From the combined Δ14C and 39Ar distributions, we derive information on the mean “isolation ages” of the deep and bottom waters of the Arctic Ocean. The data point toward mean ages of the bottom waters in the Eurasian Basin (Nansen and Amundsen Basins) of ca. 250-300 yr. The deep waters of the Amundsen Basin show slightly higher 3H concentrations than those in the Nansen Basin, indicating the addition of a higher fraction of water that has been at the sea surface during the past few decades. Correction for the bomb 14C added to the deep waters along with bomb 3H yields isolation ages for the bulk of the deep and bottom waters of the Amundsen Basin similar to those estimated for the Nansen Basin. This finding agrees well with the 39Ar data. Deep and bottom waters in the Canadian Basin (Makarov and Canada Basins) are very homogeneous, with an isolation age of ca. 450 yr. Δ14C and 39Ar data and a simple inverse model treating the Canadian Basin Deep Water (CBDW) as one well-mixed reservoir renewed by a mixture of Atlantic Water (29%), Eurasian Basin Deep Water (69%) and brine-enriched shelf water (2%) yield a mean residence time of CBDW of ca. 300 yr.
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  • 6
    Publikationsdatum: 2017-05-31
    Materialart: Article , NonPeerReviewed
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  • 7
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    Institut für Meereskunde
    In:  Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 139 . Institut für Meereskunde, Kiel, Germany, 161 pp.
    Publikationsdatum: 2013-06-27
    Materialart: Report , NonPeerReviewed
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  • 8
    Publikationsdatum: 2019-07-26
    Materialart: Report , NonPeerReviewed
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  • 9
    Publikationsdatum: 2019-09-23
    Beschreibung: The Columbia Climate Center, in partnership with World Wildlife Fund, Woods Hole Research Center, and Arctic 21, held a workshop titled A 5˚C Arctic in a 2˚C World on July 20 and 21, 2016. The workshop was co-sponsored by the International Arctic Research Center (University of Alaska Fairbanks), the Arctic Institute of North America (Canada), the MEOPAR Network (Marine Environmental Observation, Prediction, and Response), and the Future Ocean Excellence Cluster. The goal of the workshop was to advance thinking on the science and policy implications of the temperature change in the context of the 1.5 to 〈2˚C warming expected for the globe, as discussed during the 21st session of the Conference of the Parties of the United Nations Framework Convention on Climate Change at Paris in 2015. For the Arctic, such an increase means an anticipated increase of roughly 3.5 to 5˚C. An international group of 41 experts shared perspectives on the regional and global impacts of an up to +5˚C Arctic, examined the feasibility of actively lowering Arctic temperatures, and considered realistic timescales associated with such interventions. The group also discussed the science and the political and governance actions required for alternative Arctic futures.
    Materialart: Report , NonPeerReviewed
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  • 10
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    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 41 (7). pp. 1053-1068.
    Publikationsdatum: 2018-01-17
    Beschreibung: The mean residence time of river-runoff on the shelves and in the halocline of the Arctic Ocean is estimated from salinity and tracer data (tritium, 3He and the 18O/16O ratio). These estimates are derived from comparison of apparent tracer ages of the halocline waters using a combination of tracers that yield different information: (1) the tritium “vintage” age, which records the time that has passed since the river-runoff entered the shelf; and (2) the tritium/3He age, which reflects the time since the shelf waters left the shelf. The difference between the ages determined by these two methods is about 3–6 years. Correction for the initial tritium/3He age of the shelf waters (about 0.5–1.5 years) yields a mean residence time of the river-runoff on the shelves of the Siberian Seas of about 3.5 ± 2 years.
    Materialart: Article , PeerReviewed
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