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Mechanisms controlling primary and new production in a global ecosystem model Part II: The role of the upper ocean short-term periodic and episodic mixing events

Popova, E.E.; Coward, A.C.; Nurser, G.A.; de Cuevas, B.; Anderson, T.R.. 2006 Mechanisms controlling primary and new production in a global ecosystem model Part II: The role of the upper ocean short-term periodic and episodic mixing events. Ocean Science, 2 (2). 267-279.

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Abstract/Summary

The use of 6 h, daily, weekly and monthly atmospheric forcing resulted in dramatically different predictions of plankton productivity in a global 3-D coupled physicalbiogeochemical model. Resolving the diurnal cycle of atmospheric variability by use of 6 h forcing, and hence also diurnal variability in UML depth, produced the largest difference, reducing predicted global primary and new production by 25% and 10% respectively relative to that predicted with daily and weekly forcing. This decrease varied regionally, being a 30% reduction in equatorial areas primarily because of increased light limitation resulting from deepening of the mixed layer overnight as well as enhanced storm activity, and 25% at moderate and high latitudes primarily due to increased grazing pressure resulting from late winter stratification events. Mini-blooms of phytoplankton and zooplankton occur in the model during these events, leading to zooplankton populations being sufficiently well developed to suppress the progress of phytoplankton blooms. A 10% increase in primary production was predicted in the peripheries of the oligotrophic gyres due to increased storm-induced nutrient supply end enhanced winter production during the short term stratification events that are resolved in the run forced by 6 h meteorological fields. By resolving the diurnal cycle, model performance was significantly improved with respect to several common problems: underestimated primary production in the oligotrophic gyres; overestimated primary production in the Southern Ocean; overestimated magnitude of the spring bloom in the subarctic Pacific Ocean, and overestimated primary production in equatorial areas. The result of using 6 h forcing on predicted ecosystem dynamics was profound, the effects persisting far beyond the hourly timescale, and having major consequences for predicted global and new production on an annual basis.

Item Type: Publication - Article
ISSN: 18120792
Date made live: 01 Feb 2007 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/143920

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