Ecodynamics and dissolved gas chemistry routines for ocean circulation models

Interactions between oceanic nitrate ecology and circulation determine the marine distribution of dissolved, climate relevant trace gases such as dime thyl sulfide (DMS) and carbonyl sulfide (OCS), and a variety of hydrocarbon s. Our group is constructing a suite of ecosystem/reaction/transport models , which link nitrate to the chemistry of volatiles near the sea-air interfa ce. In this paper, we describe programs which will be inserted into the hig h resolution Parallel Ocean Program. Major features of the coding indude: ( 1) ecodynamics represented in seven biological compartments (phytoplankton, zooplankton, bacteria, detritus, nitrate, ammonium and dissolved organic n itrogen). Light limited primary production is computed, along with nitrogen cycling among the bioentities. (2) Photochemistry for the volatile species DMS, OCS, the methyl halides, nonmethane hydrocarbons (NMHC) and ammonia. DMS and the halides are emitted by phytoplankton, while OCS and NMHC are pr oduced by photolysis of dissolved organic material. Ammonia is exuded by an imals and bacteria. Removal mechanisms for the gases include consumption by organisms, hydrolysis, chlorination and interfacial transfer. (3) Explicit , efficient and mass conserving numerical solutions for the biological and chemical continuity equations. Production and loss forms are generalized an d automated so that they are readily applied to new constituents. Ecology a nd the chemical transformations are exposed qualitatively to begin, and are then expressed as differential and differencing equations. The structure o f the program is described in terms of the major subroutines and their purp oses. Results are provided from both one- and three-dimensional sample runs . Computational aspects such as performance and code availability are discu ssed. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.