Ecosystem behavior at Bermuda Station “S” and ocean weather station “India”: A general circulation model and observational analysis

Abstract

A model of biological production in the euphotic zone of the North Atlantic has been developed by coupling a seven‐compartment nitrogen‐based ecosystem model with a three‐dimensional seasonal general circulation model. The predicted seasonal cycles of phytoplankton, Zooplankton, bacteria, nitrate, ammonium, primary production, and particle flux have been compared to data from Bermuda Station “S” and Ocean Weather Station “India”. Bearing in mind the simplicity of the model and the paucity of data, the results are encouraging. However, deficiencies in the physical model lead to winter nitrate values at Bermuda being overestimated, and at both positions the predicted magnitude of the spring phytoplankton bloom was too high. Simulations were carried out with different detrital sinking rates and and it was found that a sinking rate of 10 m d−1 gave the best agreement with observations. The model was used to investigate the factors affecting the population growth of phytoplankton and it was found that the model supported the generally held theory that the spring bloom is initiated by the cessation of physical mixing. After the bloom, phytoplankton are controlled by Zooplankton grazing. At Ocean Weather Station “India” the model reproduced the observed high summer nitrate levels and suggested that these high values are caused by a combination of high vertical nitrate transport, ammonium inhibition of nitrate uptake, and Zooplankton grazing control. The model demonstrated the critical importance of Zooplankton in understanding ecosystem dynamics and highlights the need for more observational data on the seasonal cycles of Zooplankton biomass and growth rates.

Skill assessment of three earth system models with common marine biogeochemistry

“…Since the OCMIP effort, marine biogeochemistry models have evolved (e.g. Hood et al 2006) from models with one nutrient, one phytoplankton, one zooplankton, and one detritus (e.g., NPZD, Fasham et al 1993) to multiple phytoplankton functional types and several limiting micronutrients (e.g., Le Quéré et al 2005;Aumont and Bopp 2006). However, the OCMIP approach of comparing models with different circulation fields and the same biogeochemical model remains useful.…”

Strategies for the Simulation of Sea Ice Organic Chemistry: Arctic Tests and Development

“…Plus it is sometimes argued that consumption rates are reduced within the brine due to lack of access by larger organisms [25]. Data are not entirely lacking, however, to describe the sea ice microfauna [41,61] and routines imported from open water schemes may well be adaptable to the task [12,[94][95][96][97]. Dynamic grazing will be introduced in future experiments, but for the moment we can neither exclude nor explore the potential for competition with exudation.…”

“…Uncertainties are naturally large; error bars of a factor of three or more in either direction accompany some of the choices. The situation is typical for modern ecodynamics simulators [12][13][14]25,[57][58][94][95][96][97]109]. Formal error quantification lies beyond the scope of the present work, but is definitely warranted considering the importance of sea ice in determining planetary albedo.…”

“…But mixing and degradation in the aqueous medium lead rapidly to divergences from the norm [11,27,60]. As usual, chlorophyll is tracked by its weight ratio to the content of the algae, as in R chl/C [62,[94][95][96]. Mechanistic details extend well beyond the primary producers, so that multiple lists of related biogeochemical quantities are required.…”

NEMURO—a lower trophic level model for the North Pacific marine ecosystem

“…PlankTOM5 is a biomass-based ecosystem model that builds on the formulations by Fasham (1993) and Fasham et al (1993) among others. Such biomass-based ecosystem models are also referred to as a Fasham-, NPZD-, or JGOFS-type models.…”