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  • American Geophysical Union (AGU)  (4)
  • 1995-1999  (4)
  • 1
    Online Resource
    Online Resource
    The application of radiotracers to a study of Black Sea circulation: Validation of numerical simulations against observed weapons testing and Chernobyl 137 Cs data
    American Geophysical Union (AGU) ; 1999
    In:  Journal of Geophysical Research: Oceans Vol. 104, No. C5 ( 1999-05-15), p. 11099-11114
    Details
    In: Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), Vol. 104, No. C5 ( 1999-05-15), p. 11099-11114
    Abstract: In this paper, we use the distribution of the artificial radionuclide, 137 Cs, to investigate mixing and ventilation in the Black Sea. Timeseries data of vertical radionuclide distributions are combined with model simulations in order to follow the magnitude and depth of penetration of surface oxic water into intermediate depths, below the oxic/anoxic interface. Simulated data are produced by a three‐dimensional circulation model that includes a new parameterization of the Bosphorus inflow/plume to simulate the effects of Mediterranean water on internal mixing. A radioactive tracer model for pre‐Chernobyl 137 Cs (weapons testing 137 Cs) and Chernobyl 137 Cs is coupled to the circulation model. The model results are compared to field data collected between 1986 and 1992. The main output from the simulations is the identification of the contribution of entrainment in the mixing of surface waters into subsurface layers. The trend of tracer penetration into the deeper layers following isopycnal surfaces is well demonstrated in the model and is consistent with the known circulation and physics of the Black Sea. The correlation between the activities of radionuclides and salinity, found in the field data, is supported by the simulations. These model results illustrate that the time‐space abundance of the existing field data is sufficient for reconstructing the distribution of tracers in space and time, provided reliable estimates of Black Sea circulation exist.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1998JC900121
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1999
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    detail.hit.zdb_id: 2403298-0
    detail.hit.zdb_id: 2016800-7
    detail.hit.zdb_id: 161666-3
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
    detail.hit.zdb_id: 2016804-4
    detail.hit.zdb_id: 3094181-7
    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    The decoupling of production and particulate export in the surface ocean
    American Geophysical Union (AGU) ; 1998
    In:  Global Biogeochemical Cycles Vol. 12, No. 2 ( 1998-06), p. 297-310
    Details
    In: Global Biogeochemical Cycles, American Geophysical Union (AGU), Vol. 12, No. 2 ( 1998-06), p. 297-310
    Abstract: The relationship between primary production in the surface ocean and export of particulate organic carbon (POC) on sinking particles is examined in studies that have utilized 234 Th as a tracer of upper ocean export. Comparisons between production and export are made in a wide range of open ocean settings and seasons. The results indicate that much of the ocean is characterized by low POC export relative to primary production (export/production = ThE 〈 5–10%). Exceptions to this pattern are found during blooms at high latitudes, accompanying spring blooms at midlatitudes, and perhaps in association with more episodic export pulses. These sites of high export are most often characterized by food webs dominated by large phytoplankton, in particular diatoms. These results can be used to better parameterize surface export in biogeochemical models in order to provide a more accurate prediction of the flow of C and associated nutrients in the oceans.
    Type of Medium: Online Resource
    ISSN: 0886-6236 , 1944-9224
    URL: Article
    DOI: 10.1029/97GB03366
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1998
    detail.hit.zdb_id: 2021601-4
    SSG: 12
    SSG: 13
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Phosphorus 32, phosphorus 37, beryllium 7, and lead 210: Atmospheric fluxes and utility in tracing stratosphere/troposphere exchange
    American Geophysical Union (AGU) ; 1999
    In:  Journal of Geophysical Research: Atmospheres Vol. 104, No. D9 ( 1999-05-20), p. 11745-11754
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 104, No. D9 ( 1999-05-20), p. 11745-11754
    Abstract: The deposition of 32 P, 33 P, 7 Be, and 210 Pb was measured in individual rain events at Woods Hole, Massachusetts, from March 1996 to February 1998 and in bimonthly integrated samples from Portsmouth, New Hampshire, from March to November 1997. Annual depositional fluxes of 32 P and 33 P were 0.178 and 0.165 disintegrations per minute (dpm) cm −2 yr −1 , respectively, at Woods Hole and 0.212 and 0.175 dpm cm −2 yr −1 at Portsmouth. Beryllium 7 and 210 Pb fluxes averaged 12.8 and 1.43 dpm cm −2 yr −1 , respectively, at Woods Hole and 16.6 and 0.95 dpm cm −2 yr −1 at Portsmouth. High ratios of 33 P/ 32 P were observed in rain during severe storm events, suggesting that these isotopes trace stratosphere/troposphere exchange processes. Similar occurrences, however, were not observed in 7 Be/ 32 P, 7 Be/ 33 P, and 7 Be/ 210 Pb ratios. This indicates that there is substantial fractionation occurring among phosphorus, beryllium, and lead between time of production and atmospheric removal via precipitation.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/1998JD100101
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1999
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    detail.hit.zdb_id: 161666-3
    detail.hit.zdb_id: 161667-5
    detail.hit.zdb_id: 2969341-X
    detail.hit.zdb_id: 161665-1
    detail.hit.zdb_id: 3094268-8
    detail.hit.zdb_id: 710256-2
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    detail.hit.zdb_id: 3094181-7
    detail.hit.zdb_id: 3094219-6
    detail.hit.zdb_id: 3094167-2
    detail.hit.zdb_id: 2220777-6
    detail.hit.zdb_id: 3094197-0
    SSG: 16,13
    Location Call Number Limitation Availability
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Iron‐stimulated changes in 13 C fractionation and export by equatorial Pacific phytoplankton: Toward a paleogrowth rate proxy
    American Geophysical Union (AGU) ; 1999
    In:  Paleoceanography Vol. 14, No. 5 ( 1999-10), p. 589-595
    Details
    In: Paleoceanography, American Geophysical Union (AGU), Vol. 14, No. 5 ( 1999-10), p. 589-595
    Abstract: We present δ 13 C values for phytol, an algal biomarker, which document up to 7 per mil isotopic enrichment during the IronEx II iron fertilization experiment. We evaluate these data using a laboratory‐derived 13 C fractionation model and show this variability is largely the result of elevated growth rates. Isotopic enrichment and stimulation of growth rate were accompanied by a sevenfold increase in the export of particulate organic carbon as estimated from 234 Th activities. This is the first direct evidence that enhanced productivity following iron enrichment can lead to both increased export of organic matter and an associated isotopic signal in an algal biomarker. On the basis of these results, we propose biomarker isotopic data be used in conjunction with paleo‐CO 2 records to reconstruct paleogrowth rates. This approach provides a means to test for iron‐stimulated changes in algal growth in sedimentary records.
    Type of Medium: Online Resource
    ISSN: 0883-8305 , 1944-9186
    URL: Article
    DOI: 10.1029/1999PA900026
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1999
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    SSG: 16,13
    SSG: 13
    Location Call Number Limitation Availability
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    Online Resource
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