Reconstruction of food conditions for Northeast Atlantic bivalve species based on Dynamic Energy Budgets     

Vnia Freitas  Joana F.M.F. Cardoso  Sílvia Santos  Joana Campos  Jan Drent  Sofia Saraiva  Johannes IJ. Witte  Sebastiaan A.L.M. Kooijman  Henk W. Van der Veer 《Journal of Sea Research》2009,62(2-3):75

Required assimilated energy to support observed growth was reconstructed for four common bivalve species (Mya arenaria, Cerastoderma edule, Mytilus edulis and Macoma balthica) from various Northeast Atlantic coastal areas, along the species distributional range. The approach applied was based on the Dynamic Energy Budget (DEB) theory whereby observed growth patterns in the field, in combination with prevailing temperatures, were used to reconstruct the average food intake experienced in the field scaled to the maximum possible. For all species, results suggest food limitation over the range of locations. In general, reconstructed food intake indicated better conditions for C. edule compared to the other species, while M. edulis presented the lowest food conditions in all the areas. Despite the indications for a latitudinal trend in primary production, no clear pattern or relationship between reconstructed food conditions and latitude was observed suggesting that any trend may be overruled by local conditions.  相似文献   

Sensitivity of the Atlantic meridional overturning circulation to South Atlantic freshwater anomalies     

Andrea A. Cimatoribus  Sybren S. Drijfhout  Matthijs den Toom  Henk A. Dijkstra 《Climate Dynamics》2012,39(9-10):2291-2306

The sensitivity of the Atlantic Meridional Overturning Circulation (AMOC) to changes in basin integrated net evaporation is highly dependent on the zonal salinity contrast at the southern border of the Atlantic. Biases in the freshwater budget strongly affect the stability of the AMOC in numerical models. The impact of these biases is investigated, by adding local anomaly patterns in the South Atlantic to the freshwater fluxes at the surface. These anomalies impact the freshwater and salt transport by the different components of the ocean circulation, in particular the basin-scale salt-advection feedback, completely changing the response of the AMOC to arbitrary perturbations. It is found that an appropriate dipole anomaly pattern at the southern border of the Atlantic Ocean can collapse the AMOC entirely even without a further hosing. The results suggest a new view on the stability of the AMOC, controlled by processes in the South Atlantic.  相似文献   

The role of hand calculations in ground water flow modeling   总被引：1，自引：0，他引：1  

Haitjema H 《Ground water》2006,44(6):786-791

Most ground water modeling courses focus on the use of computer models and pay little or no attention to traditional analytic solutions to ground water flow problems. This shift in education seems logical. Why waste time to learn about the method of images, or why study analytic solutions to one-dimensional or radial flow problems? Computer models solve much more realistic problems and offer sophisticated graphical output, such as contour plots of potentiometric levels and ground water path lines. However, analytic solutions to elementary ground water flow problems do have something to offer over computer models: insight. For instance, an analytic one-dimensional or radial flow solution, in terms of a mathematical expression, may reveal which parameters affect the success of calibrating a computer model and what to expect when changing parameter values. Similarly, solutions for periodic forcing of one-dimensional or radial flow systems have resulted in a simple decision criterion to assess whether or not transient flow modeling is needed. Basic water balance calculations may offer a useful check on computer-generated capture zones for wellhead protection or aquifer remediation. An easily calculated "characteristic leakage length" provides critical insight into surface water and ground water interactions and flow in multi-aquifer systems. The list goes on. Familiarity with elementary analytic solutions and the capability of performing some simple hand calculations can promote appropriate (computer) modeling techniques, avoids unnecessary complexity, improves reliability, and is likely to save time and money. Training in basic hand calculations should be an important part of the curriculum of ground water modeling courses.  相似文献   

Groundwater Grows     

Henk M. Haitjema 《Ground water》2014,52(3):325-325

  相似文献   

Relative sea-level rise and the conterminous United States: Consequences of potential land inundation in terms of population at risk and GDP loss   总被引：1，自引：0，他引：1  

Toon Haer  Eugenia Kalnay  Michael Kearney  Henk Moll 《Global Environmental Change》2013,23(6):1627-1636

Global sea-level rise poses a significant threat not only for coastal communities as development continues but also for national economies. This paper presents estimates of how future changes in relative sea-level rise puts coastal populations at risk, as well as affect overall GDP in the conterminous United States. We use four different sea-level rise scenarios for 2010–2100: a low-end scenario (Extended Linear Trend) a second low-end scenario based on a strong mitigative global warming pathway (Global Warming Coupling 2.6), a high-end scenario based on rising radiative forcing (Global Warming Coupling 8.5) and a plausible very high-end scenario, including accelerated ice cap melting (Global Warming Coupling 8.5+). Relative sea-level rise trends for each US state are employed to obtain more reasonable rates for these areas, as long-term rates vary considerably between the US Atlantic, Gulf and Pacific coasts because of the Glacial Isostatic Adjustment, local subsidence and sediment compaction, and other vertical land movement. Using these trends for the four scenarios reveals that the relative sea levels predicted by century's end could range – averaged over all states – from 0.2 to 2.0 m above present levels. The estimates for the amount of land inundated vary from 26,000 to 76,000 km². Upwards of 1.8 to 7.4 million people could be at risk, and GDP could potentially decline by USD 70–289 billion. Unfortunately, there are many uncertainties associated with the impact estimates due to the limitations of the input data, especially the input elevation data. Taking this into account, even the most conservative scenario shows a significant impact for the US, emphasizing the importance of adaptation and mitigation.  相似文献   

Three-Dimensional Structure of Optimal Nonlinear Excitation for Decadal Variability of the Thermohaline Circulation          下载免费PDF全文

ZU Zi-Qing  MU Mu  Henk A.DIJKSTRA 《大气和海洋科学快报》2013,(6):410-416

The decadal variability of the North Atlantic thermohaline circulation（THC） is investigated within a three-dimensional ocean circulation model using the conditional nonlinear optimal perturbation method. The results show that the optimal initial perturbations of temperature and salinity exciting the strongest decadal THC variations have similar structures： the perturbations are mainly in the northwestern basin at a depth ranging from 1500 to 3000 m. These temperature and salinity perturbations act as the optimal precursors for future modifications of the THC, highlighting the importance of observations in the northwestern basin to monitor the variations of temperature and salinity at depth. The decadal THC variation in the nonlinear model initialized by the optimal salinity perturbations is much stronger than that caused by the optimal temperature perturbations, indicating that salinity variations might play a relatively important role in exciting the decadal THC variability. Moreover, the decadal THC variations in the tangent linear and nonlinear models show remarkably different characteristics, suggesting the importance of nonlinear processes in the decadal variability of the THC.  相似文献   

The use of scenarios as the basis for combined assessment of climate change mitigation and adaptation   总被引：1，自引：0，他引：1  

Detlef P. van Vuuren  Morna IsaacZbigniew W. Kundzewicz  Nigel ArnellTerry Barker  Patrick CriquiFrans Berkhout  Henk HilderinkJochen Hinkel  Andries HofAlban Kitous  Tom KramReinhard Mechler  Serban Scrieciu 《Global Environmental Change》2011,21(2):575-591

Scenarios are used to explore the consequences of different adaptation and mitigation strategies under uncertainty. In this paper, two scenarios are used to explore developments with (1) no mitigation leading to an increase of global mean temperature of 4 °C by 2100 and (2) an ambitious mitigation strategy leading to 2 °C increase by 2100. For the second scenario, uncertainties in the climate system imply that a global mean temperature increase of 3 °C or more cannot be ruled out. Our analysis shows that, in many cases, adaptation and mitigation are not trade-offs but supplements. For example, the number of people exposed to increased water resource stress due to climate change can be substantially reduced in the mitigation scenario, but adaptation will still be required for the remaining large numbers of people exposed to increased stress. Another example is sea level rise, for which, from a global and purely monetary perspective, adaptation (up to 2100) seems more effective than mitigation. From the perspective of poorer and small island countries, however, stringent mitigation is necessary to keep risks at manageable levels. For agriculture, only a scenario based on a combination of adaptation and mitigation is able to avoid serious climate change impacts.  相似文献   

Transverse structure of tidal and residual flow and sediment concentration in estuaries     

Karin M. H. Huijts  Huib E. de Swart  George P. Schramkowski  Henk M. Schuttelaars 《Ocean Dynamics》2011,61(8):1067-1091

An analytical and a numerical model are used to understand the response of velocity and sediment distributions over Gaussian-shaped estuarine cross-sections to changes in tidal forcing and water depth. The estuaries considered here are characterized by strong mixing and a relatively weak along-channel density gradient. It is also examined under what conditions the fast, two-dimensional analytical flow model yields results that agree with those obtained with the more complex three-dimensional numerical model. The analytical model reproduces and explains the main velocity and sediment characteristics in large parts of the parameter space considered (average tidal velocity amplitude, 0.1–1 m s^− 1 and maximum water depth, 10–60 m). Its skills are lower for along-channel residual flows if nonlinearities are moderate to high (strong tides in deep estuaries) and for transverse flows and residual sediment concentrations if the Ekman number is small (weak tides in deep estuaries). An important new aspect of the analytical model is the incorporation of tidal variations in the across-channel density gradient, causing a double circulation pattern in the transverse flow during slack tides. The gradient also leads to a new tidally rectified residual flow component via net advection of along-channel tidal momentum by the density-induced transverse tidal flow. The component features landward currents in the channel and seaward currents over the slopes and is particularly effective in deeper water. It acts jointly with components induced by horizontal density differences, Coriolis-induced tidal rectification and Stokes discharge, resulting in different along-channel residual flow regimes. The residual across-channel density gradient is crucial for the residual transverse circulation and for the residual sediment concentration. The clockwise density-induced circulation traps sediment in the fresher water over the left slope (looking up-estuary in the northern hemisphere). Model results are largely consistent with available field data of well-mixed estuaries.  相似文献   

Spatial distribution patterns of the peppery furrow shell Scrobicularia plana (da Costa, 1778) along the European coast: A review     

Sílvia Santos  Pieternella C. Luttikhuizen  Joana Campos  Carlo H.R. Heip  Henk W. van der Veer 《Journal of Sea Research》2011,66(3):238-247

The bivalve Scrobicularia plana is an important species of shallow water benthic communities with a wide geographic distribution but also with a general patchy pattern, i.e. irregular in occurrence and in density. This review aims to determine the processes responsible for the species' spatial distribution pattern based on the available information on S. plana. Although several pre- and post-settlement processes are believed to influence spatial patterns of marine invertebrates, the general patchy distribution of S. plana seems to be determined by the existence of specific environmental conditions during settlement. Factors such as temperature, salinity, sediment type, hydrographic conditions and predation affect settlement and spat survival and not one but a combination of factors seems to explain the species distribution pattern. Future work should focus on determining the scale of patchiness, using hierarchical sampling, as well as the connectivity between populations by analysing the population genetic structure.  相似文献   

On the attractors of an intermediate coupled ocean-atmosphere model     

Henk A. Dijkstra  J. David Neelin 《Dynamics of Atmospheres and Oceans》1995,22(1-2)

Techniques of numerical bifurcation theory are used to study stationary and periodic solutions of an intermediate coupled model for tropical ocean-atmosphere interaction. The qualitative dynamical behavior is determined for a volume in parameter space spanned by the atmospheric damping length, the coupling parameter, the surface layer feedback strength and the relative adjustment time coefficient. Time integration methods have previously shown much interesting dynamics, including multiple steady states, eastward- or westward-propagating orbits and relaxation oscillations. The present study shows how this dynamics arises in parameter space through the interaction of the different branches of equilibrium solutions and the singularities on these branches. For example, we show that westward-propagating periodic orbits arise through an interaction of two unstable stationary modes and that relaxation oscillations occur through a limit cycle-saddle node interaction. There are several dynamical regimes in the coupled model which are determined by the primary bifurcation structure; this structure depends strongly on the parameters in the model. Although much of the dynamics may be studied in the fast-wave limit, it is shown that ocean wave dynamics introduces additional oscillatory instabilities and how these relate to propagating oscillations.  相似文献