http://hdl.handle.net/1834/260 Thu, 16 May 2013 04:50:20 GMT 2013-05-16T04:50:20Z http://hdl.handle.net/1834/271 Title: Biophysical isopycnic-coordinate modelling of plankton dynamics in the Arabian Sea Authors: Idrisi, N.; Romanou, A.; Olascoaga, M.J. Abstract: A Nutrients-Phytoplankton-Zooplankton-Detritus (NPZD) ecosystem model is coupled to the Miami Isopycnic-Coordinate Ocean Model (MICOM) to study planktondynamics in the Arabian Sea. Experiments oriented to testing the NPZD-MICOM coupled model sensitivity to variations in several parameters are performed. Particular attention is paid to the rates of detritus sinking and maximum phytoplankton growth rate. The coarse features of the blooms are captured by all the experiments considered, and agree with earlier models for the biological activity of the region. Intensity, duration, and peaks of the blooms are found to be quite sensitive to the parameter choices. The existence of an offshore deep chlorophyll maximum in the model is found to be closely related to the increase of the detritus sinking rate. The use of temperature-dependent maximum growth rate of phytoplankton and the increase of detritus sinking rate are shown to improve model results compared with in situ and satellite observations. The differences between the present results and those from previous modelling efforts in the region, where few- or multi-layer hydrodynamical models or even fixed-level hydrodynamical models have been employed, are found to be in the same range as the differences among the results from the various sensitivity experiments presented here. This indicates that a small uncertainty in the knowledge of the ecosystem model parameters can be more important in ecosystem modelling than the uncertainty associated to the differences in the vertical coordinate representation of the underlying hydrodynamical model. There are still biological processes, such as denitrification which a®ect the vertical distribution of nutrient concentrations, that are not included neither in the previous works in the area nor in the present work. This might mask any potential advantages of the present MICOM-NPZD coupled model, especially at mid-depths in the ocean. Thu, 07 Jul 2005 00:00:00 GMT http://hdl.handle.net/1834/271 2005-07-07T00:00:00Z http://hdl.handle.net/1834/512 Title: Internal Atmospheric Dynamics and Tropical Indo-Pacific Climate Variability Authors: Kinter, S.M.; Pegion, K.; Kirtman, B.P. Abstract: One possible explanation for tropical sea surface temperature (SST) interannual variability is that it can be accurately described by a linear auto-regressive model with damped coupled feedbacks and stochastic forcing. This auto-regressive model can be viewed is a “null hypothesis” for tropical SST variability. This paper advances a new coupled general circulation model (CGCM) coupling strategy, called an interactive ensemble as a method to test this null hypothesis. The design of the interactive ensemble procedure is to reduce the stochastic variability in the air-sea fluxes applied to the ocean component while retaining the deterministic component of the coupled feedbacks. The interactive ensemble procedure uses multiple realizations of the atmospheric GCM coupled to a single realization of the ocean GCM. The ensemble mean of the atmospheric GCM fluxes are applied to the ocean model thereby significantly reducing the variability due to internal atmospheric dynamics in the air-sea fluxes. If the null hypothesis is correct, the SST variability is reduced, and the auto-regressive model defines how much the variability should be reduced. In order to test the null hypothesis, we apply the interactive ensemble procedure to a heuristic coupled model. We then use the heuristic coupled model to interpret the CGCM interactive ensemble results with respect to: (i) SST variance and (ii) how the amplitude of atmospheric internal dynamics depends on the evolving background SST anomaly. There are significant regions where the heuristic model fails to reproduce the CGCM results, suggesting that aspects of tropical Indo-Pacific variability in the CGCM cannot be explained by damped coupled feedbacks and stochastic forcing. These regions are largely coincident with regions of large convective anomalies. Surprisingly, we also find significant regions in the tropical eastern Pacific where the variability due to internal ocean dynamics cannot be neglected. Wed, 26 Jan 2005 00:00:00 GMT http://hdl.handle.net/1834/512 2005-01-26T00:00:00Z http://hdl.handle.net/1834/641 Title: Indian Ocean Safari Authors: Fuller, K.S. Abstract: For most activities, a relatively low level of exertion is required. While the ship will sometimes dock for a dry landing, you will need to climb into and out of Zodiacs for certain excursions ashore and for some snorkeling and most diving activities. Staff and crew will be on hand to assist. On shore excursions, you must be able to walk moderate distances in villages, towns, forests, and on beaches, occasionally over rough terrain. Opportunities will be available for leisurely strolls, as well as optional hikes requiring more exertion. Birders may participate in ornithological excursions. Our expedition staff and renowned lecture team of naturalists and historians will accompany you throughout shore and afloat. Average daily temperatures will be in the 80s F, with the possibility of occasional afternoon showers. A complete list of recommended clothing, essentials to bring, and a suggested reading list will be mailed to you approximately four months prior to departure. Exact ship arrival times are often dependent upon winds and currents. Participants will most enjoy these remarkable destinations if they travel with a spirit of adventure and flexibility. Sat, 01 Jan 2005 00:00:00 GMT http://hdl.handle.net/1834/641 2005-01-01T00:00:00Z http://hdl.handle.net/1834/703 Title: The Role of Sea-Level Rise in the Formation of Peatlands in Maputaland Authors: Grundling, P.L. Abstract: Peatlands act as information traps; archives reflecting changes in climate and environment, through pollen assemblages, sediment facies, plant fibre and C14 dating. The investigation of Maputaland peatlands presents an ideal opportunity to understand these changes during the Late Pleistocene and Holocene. The Maputaland peatlands in South Africa could be geographically divided into two distribution areas based on age: The Holocene age peatlands northwards of the Mkuze River inflow into Lake St. Lucia and the Late Pleistocene age peatlands south of this inflow. The grouping of peat thicknesses versus peat ages in a scatter diagram indicates distribution deviations from the ideal accumulation line. These might represent periods of low or negative growth and periods of positive or high rates of peat accumulation linked to changing climatic and ecological environments during the development of these peatlands. Erosional and depositional events appear to be closely related to local sea-level fluctuations during the Holocene. Periods of optimum peat accumulation correspond with Holocene sea-level maxima. Mon, 01 Nov 2004 00:00:00 GMT http://hdl.handle.net/1834/703 2004-11-01T00:00:00Z