Dissertation

Survey of a Marine Biogeochemical Model Hierarchy: Global Dissolved Organic Carbon

Mendis Jayasinghe, Amadini

2021

Overview

Geophysical and geochemical models are used to represent complex processes taking place in various compartments of the earth system. The programs require separate evaluation of component behavior, internal biases, feedbacks and detailed mechanisms in order to achieve best performance. A way to handle the separation is by layering down the inherent spatial dimensions from three to two and so forth toward convenient, manageable reduced forms. In this dissertation, we present a set of streamlined simulations that are scaled-down across the usual geo-coordinates for use in evaluating a series of carbon cycle applications. We focus in particular on the global cycling of aqueous dissolved organics. We begin with the simplest model type: a zero-dimensional box designed to evaluate tropical marine emissions of isoprene into the lower troposphere. A simple chemical dynamic study has been conducted in this first case: steady-state calculations were performed for short-lived atmospheric species. Peripheral results suggest prominent isoprene leveraging in coastal regions. The numerics behind our solutions are also evaluated. Next we move on to the study of sub-tropical two-dimensional monoterpene emissions. Along with a global budgeting exercise, vertical and horizontal steady-state calculations were performed to estimate sea air fluxes. Subtropical monoterpene release and potential SOA (Secondary Organic Aerosol) source patterns were identified. Next, the macromolecular role of surface-active dissolved organics oriented at the sea-air interface has been assessed. The resultant impact suggested connections between organic chemistry and a lowering of microwave scale ripple heights, with implications for the altimetric sigma bloom phenomenon. In a last application, we transition to northern high latitudes, where a Lagrangian computation for the chemical evolution of riverine organics was conducted. We evaluated fluvial interactions along an idealized arctic river, with the potential for biophysical influences across high latitude coastal regions. Significant parameters in this instance: the aqueous kinetics, dilution, tributary mixing, sub-ecological changes, and coastal biophysical influences -all with evolution from artic soil to ocean. In this overall hierarchy of reduced models, we start from the tropics and migrate our calculations toward more climatologically sensitive high latitudes -even approaching the northern pole. As a future direction, we identify further studies needed in boreal regions since the latter are by far the most sensitive areas of the earth system given current global warming trends. Specifically we find that the chemistry of artic rivers points to further study from start to finish. Here the aqueous organic chemistry demands greater attention from soil reactions through the tributary network extending to the coastal areas.

• Publisher: ProQuest Dissertations & Theses
• Subject: Biogeochemistry / Chemistry
• ISBN: 9798496560337