Data-driven exploration of the variability, controls and future changes
of dimethyl sulfide in the global surface ocean
Abstract
As the largest natural source of sulfur-containing gases into the
atmosphere, ocean organism-derived dimethyl sulfide (DMS) has been
considered to play a critical role in the Earth’s climate system. Yet
there are great uncertainties in modeling the spatiotemporal variations
of DMS and incomplete knowledge of influencing factors in different
oceanic regions. Moreover, little is known about the future change of
global DMS, which limits our understanding of the feedback of marine
ecosystem to climate change. Here we develop an artificial neural
network model and combine data mining approaches to address these
issues. Phytoplankton biomass and salinity are currently predominant
factors associated with DMS variability in the coastal and Arctic
regions, respectively. In the mid- and low-latitude open oceans,
nutrients and temperature are also crucial factors in addition to
radiation and mixed layer depth, and their relationships with DMS show
reversals when passing certain thresholds. Although the global average
DMS concentration and emission slightly decline from 2005 to 2100, they
may change considerably in specific regions. In contrast to the DMS
decreases in the low-latitudes mainly related with phosphate reduction
and temperature rise and in the North Atlantic subpolar gyre attributed
to salinity decline, warming will cause DMS increase in the Southern
Ocean and sea ice loss will dramatically enhance DMS emission in the
Arctic. Although the global negative feedback loop between oceanic DMS
and climate may not operate, the future spatial redistribution of DMS
may lead to the change in cloud cover pattern and significantly affect
regional climate.