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The distribution of reduced sulphur compounds in polar environments : insights from observations and climatologies

University of British Columbia

Dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) are key components in the marine reduced sulphur cycle, where they play several roles in the ecology of bacteria and phytoplankton. Upon emission to the atmosphere, DMS plays a role in atmospheric sulphur budgets and radiative balance, having potentially climate-cooling effects. This thesis aims to provide insight into the distribution of these compounds in polar marine waters. This is done by constructing a revised climatology of DMS budgets in the Southern Ocean and by presenting new DMS/P data in the Arctic Ocean. Chapter 2 presents a revised summertime climatology of DMS distributions and fluxes in the Southern Ocean, based on the inclusion of a significant number of high-resolution measurements (~700 000) made in recent years. Based on the climatology written by Lana et al in 2011, the revised climatology shows notable differences in DMS budgets. In particular, we find increased DMS concentrations and sea–air fluxes south of the Polar Frontal zone (between 60 and 70°S), and increased sea–air fluxes in mid-latitude waters (40–50°S). These changes are attributable to both the inclusion of new data and the use of region-specific parameters (e.g. data cut-off thresholds and interpolation radius) in our objective analysis. DMS concentrations in the Southern Ocean exhibit weak though statistically significant correlations with several oceanographic variables, including ice cover, mixed-layer depth and chlorophyll-a. Chapter 3 presents new DMS and DMSP measurements made in the Canadian sector of the Arctic Ocean on the 2015 GEOTRACES expedition, as well as estimates of sea-air fluxes and hydrographic data that presents some potential explanations for these distributions. Across the full sampling transect, we find weak relationships between DMSP:chl a ratios and known diatom marker pigments and elevated DMS/P in partially ice-covered areas. Our high spatial resolution measurements allowed us to examine DMS variability over small scales, and to document DMS concentration gradients across surface hydrographic frontal features. Together, these two chapters help to fill out the understanding of the distribution and cycling of reduced sulphur in polar marine waters, and can serve to provide a baseline for future reduced sulphur work in these regions.

Text

2016-04-28

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/57957

Oceanography

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/