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  • 1
    Book
    Book
    Der Einfluss der Wärmebilanz auf die Struktur der saisonalen Grenzschicht : = The role of the heat budget in the seasonal boundary layer (1987)
    Kiel : Inst. f. Meereskunde, Abt. Regionale Ozeanographie
    Details Availability
    Keywords: Buch Book ; Bericht Hochschulschrift ; Serienstueck ; Einteiler ; Dissertation ; Report ; Hochschulschrift ; Bericht
    Type of Medium: Book
    Pages: X, 161, 8 S. , graph. Darst., Kt.
    Series Statement: Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität, Kiel 171
    Language: German , English , English
    Note: X [ 10 ] zehn, 161 einhunderteinundsechzig, 8 acht Seiten : graphische grafische Darsteellung Darstellungen , Zugl.: Kiel, Univ., Diss. : 1987 , Literaturverz. S. 152 - 161 , Mit engl. Zsfassung.
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  • 2
    Online Resource
    Online Resource
    Der Einfluß der Wärmebildung auf die Struktur der saisonalen Grenzschicht (1986)
    Kiel
    Details Availability
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: Online-Ressource (169 Seiten = 7 MB) , Graphen, Karten
    URL: https://oceanrep.geomar.de/22123/
    Language: German
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  • 3
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    The response of the upper ocean to solar heating. I: The mixed layer (1986)
    Royal Meteorological Society
    In:  Quarterly Journal of the Royal Meteorological Society, 112 (471). pp. 1-27.
    Details
    Publication Date: 2019-01-21
    Description: The results of two earlier papers on convection in the mixed layer and on the solar heating profile are here introduced into a one-dimensional model in order to investigate the following consequences of the daily cycle of solar heating in the upper ocean: 1. the daytime convection depth becomes less than the turbocline depth; 2. the convective power supply to turbulence in the mixed layer is reduced; 3. the mixed layer below the convection layer becomes stably stratified; 4. the depth of the turbocline is reduced, leaving a diurnal thermocline between it and the top of the seasonal thermocline; 5. the heat content and potential energy of the diurnal and seasonal thermoclines are increased, slowing down the subsequent nocturnal descent of the turbocline. These diurnal changes are illustrated by integrating a one-dimensional model forced by the astronomical cycle of solar heating and seasonal variation of surface meteorology derived from Bunker's climatology. The model is integrated for 18 months to show the seasonal modulation of the diurnal cycle. Nocturnal convection plays a dominant role. The convection depth closely follows the thermal compensation depth during the day when they are less than the turbocline depth. Integrating the model with a 24-hour time step leads to large errors in the seasonal variation of mixed layer temperature and depth, and in the source term of isopycnic potential vorticity. The errors are reduced by using two time steps per day, one for the daytime when convection is quenched, the other for the night when it is active. A novel parametrization based on tuning the daily equivalent solar elevation to surface temperature further reduces the error. This parametrization is used to investigate the sensitivity of the seasonal cycles of mixed layer depth and temperature to: (1) seasonality in the surface fluxes; (2) systematic changes in the net annual solar heating; (3) random changes in the seasonal cycles of solar heating induced (i) monthly and (ii) daily. The sensitivity to uncertainty in seawater turbidity is investigated in the same way. The profile of isopycnic potential vorticity subducted into the thermocline depends on the vernal correlation of mixed layer depth and density, so gyre circulation is sensitive to solar heating in spring.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/qj.49711247102
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Simulating Plankton Ecosystems by the Lagrangian Ensemble Method (1994)
    In:  Philosophical Transactions of the Royal Society B: Biological Sciences, 343 (1303). pp. 27-31.
    Details
    Publication Date: 2020-06-11
    Description: Understanding the plankton ecosystem in the ocean requires detailed demographic analysis. It is impossible to sample the ocean adequately for such analysis, but progress can be made by analysing data sets generated by mathematical models provided they realistically simulate the ecosystem. The Lagrangian Ensemble method is well suited to demographic studies because it generates large data sets containing complete information on all the families living in the simulated ecosystem. It provides audit trails of individual families for unambiguous analysis of mechanisms responsible for the simulated changes in community and environment. Recent papers based on the Lagrangian Ensemble method are reviewed.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1098/rstb.1994.0004
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Diatom demography in winter – simulated by the Lagrangian Ensemble method (1993)
    Wiley
    In:  Fisheries Oceanography, 2 (3-4). pp. 202-222.
    Details
    Publication Date: 2017-01-06
    Description: According to Sverdrup's (1953) model of the spring bloom, phytoplankton biomass decreases in winter when the mixed layer depth exceeds the critical depth. We have used a one-dimensional mathematical model integrated by the Lagrangian Ensemble method to simulate a population of diatoms during the winter between two growing seasons off the Azores. The model allows us to diagnose the demographic changes in the simulated diatom population from a variety of perspectives. The total population falls to a minimum of 70 million diatoms m-2 at the end of February. The vertical distribution of the population dynamics is first analysed in terms of daily Eulerian averages over 1 m depth intervals. Growth starts in February when the diurnal thermocline becomes shallower than 50 m, but while the mixed layer is still 200 m deep. The natural mortality has a minimum in winter because it is reduced (in the model) with temperature and population density. Eulerian analysis suggests that in winter, diatoms have a life expectancy of more than 3 months, so a significant number will survive the months of December, January and February when there is very little growth. Losses to grazing are negligible in winter. Lagrangian analysis shows how an individual diatom responds to its changing ambient environment caused by variation in depth (due to turbulent mixing) and the diurnal and seasonal changes in the photosynthetically active radiance. The different trajectories followed by the thousands of plankton particles simulated by the model produce diversity in growth rate ranging over several orders of magnitude, so care has to be taken in statistical analysis. The paper ends with a re-assessment of the value of the critical depth and compensation depth as predictors for onset of the spring bloom. The compensation depth was computed by Eulerian averaging over 1 m depth inter-vals each day. For 1 month after the vernal equinox the compensation depth follows the ascent of the mixed layer as it rises from a depth of 100 m to 40 m. Lagrangian analysis reveals that this is due to the photo-adaptation better matching the ambient irradiance experienced by diatoms in the mixed layer compared with those at the same depth in the seasonal thermo-cline. By mid-April the spring bloom has already ad-vanced so far that self shading influences the compensation depth, which then rises into the mixed layer. We conclude that Sverdrup's criterion is not useful for predicting changes in the diatom population simulated by our model.
    Type: Article , PeerReviewed
    DOI: 10.1111/j.1365-2419.1993.tb00136.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    The plankton multiplier—positive feedback in the greenhouse (1993)
    Oxford Univ. Press
    In:  Journal of Plankton Research, 15 (9). pp. 1053-1074.
    Details
    Publication Date: 2018-05-30
    Description: The plankton multiplier is a positive feedback mechanism linking the greenhouse effect and biological pump (Woods.J.D., Royal Commission on Environmental Pollution, 1990). As pollution increases the atmospheric concentration of carbon dioxide, the enhanced greenhouse effect induces radiative forcing of the ocean, which diminishes the depth of winter convection, reducing the annual resupply of nutrients to the euphotic zone and therefore the annual primary production. That weakens the biological pump, which contributes to oceanic uptake of CO2,. As the ocean takes up less CO2, more remains in the atmosphere, accelerating the rise in radiative forcing. We have used a mathematical model of the upper ocean ecosystem, based on the Lagrangian Ensemble method, to estimate the sensitivity of the biological pump to radiative forcing, which lies at the heart of the plankton multiplier. We conclude that increasing radiative forcing by 5 W m− (equivalent to doubling atmospheric CO2) reduces the deep flux of paniculate carbon by 10%. That sensitivity is sufficient to produce significant positive feedback in the greenhouse. It means that the plankton multiplier will increase the rate of climate change in the 21st century. It also suggests that the plankton multiplier is the mechanism linking the Milankovich effect to the enhanced greenhouse effect that produces global warming at the end of ice ages.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1093/plankt/15.9.1053
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Mixed layer and Ekman current response to solar heating (1985)
    Reidel
    In:  In: The oceanic surface: wave Breaking, Turbulent Mixing and radio Probing. , ed. by Toba, Y. and Mitsuvasu, H. Reidel, Dordrecht, pp. 487-507.
    Details
    Publication Date: 2012-06-18
    Type: Book chapter , NonPeerReviewed
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    OceanRep: Book chapter
  • 8
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    A Lagrangian mixed layer model of Atlantic 18 C water formation (1986)
    Nature Publishing Group
    In:  Nature, 319 . pp. 574-576.
    Details
    Publication Date: 2019-01-21
    Description: One of the most striking features of the upper North Atlantic Ocean is an extensive layer of water with temperature close to 18°C and salinity close to 36.5‰, (ref. 1). This 18°C water is formed by winter convection in the Sargasso sea2,3, but aspects of the annual rate of 18°C water formation remain obscure4. We have simulated this water mass formation by integrating a one-dimensional model along a 4-yr trajectory of a water column circulating around the Sargasso Sea. Winter convection is deep (≥200 m) in regions where the ocean suffers a net annual heat loss to the atmosphere, and shallow (≤lOOm) where the ocean gains heat each year. The origin of the thermostad (nearly isothermal layer) is a thick layer of nearly homogeneous water subducted beneath the seasonal boundary layer in the year that the water column passes through the line dividing annual cooling from annual heating. We estimate the annual production of 18°C water to be 446,000 km3 yr−1. Downstream, more stratified central water is formed each year at a rate that depends more on Ekman pumping (wind-forced convergence) than on the decreasing depth of winter convection
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1038/319574a0
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Der Einfluß der Wärmebildung auf die Struktur der saisonalen Grenzschicht (1987)
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 161 pp . Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel, 171 . DOI 10.3289/ifm_ber_171 〈http://dx.doi.org/10.3289/ifm_ber_171〉.
    Details
    Publication Date: 2013-10-16
    Type: Thesis , NonPeerReviewed
    Format: text
    DOI: 10.3289/ifm_ber_171
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    OceanRep: Thesis - not published by a publisher
  • 10
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    Primary production, respiration and stratification in the ocean (1994)
    AGU (American Geophysical Union)
    In:  In: The Polar Oceans and Their Role in Shaping the Global Environment. , ed. by Johannessen, O. M., Muench, R. D. and Overland, J. E. Geophysical Monograph Series, 85 . AGU (American Geophysical Union), pp. 247-254.
    Details
    Publication Date: 2012-07-12
    Description: The current status of the Sverdrup theory for the initiation of plankton blooms is examined. A prescription is given for the computation of the Sverdrup critical depth, using recently-published algorithms for mixed-layer primary production and a generalised loss term. Using no further information, the intrinsic rate of increase of phytoplankton biomass in the mixed layer can also be found. This rate, compared against the local frequency of storm occurrence, provides an alternative criterion for the initiation of blooms. The Eulerian (bulk property) methods used to derive these results are contrasted with the Lagrangian Ensemble method. The Lagrangian approach provides one avenue to the elaboration of the Sverdrup criterion to include the effect of processes with characteristic timescales small compared to one day. The incidence of blooms in the apparent absence of vertical stratification is reviewed: it is concluded that these observations do not undermine the basic logic of the Sverdrup theory. However, they do provoke interest in a re-examination of the feedbacks between the physical and biological dynamics in the mixed layer: an example is given. Finally, suggestions are made for further work in this subject area.
    Type: Book chapter , NonPeerReviewed
    DOI: 10.1029/GM085p0247
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    OceanRep: Book chapter
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