Life on the Margins: Dynamic Changes along Sea Ice and Coastal Margins as Observed from Space

This thesis has highlighted the dynamic and interconnected nature of biogeochemical processes at the boundaries of sea ice edges, coastal margins, and open watersheds as observed from space. The combined use of satellite-derived datasets has offered new insights into the physical and biological mechanisms governing these critical zones. Notably, the analysis of Antarctic sea ice edges revealed that changes in sea ice dynamics are influencing phytoplankton blooms, with implications for biogeochemical modeling as the Southern Ocean experiences warming and freshening. In the Arctic, a clear synchrony between terrestrial and marine productivity has been identified, with both domains experiencing a simultaneous rise in primary productivity, closely tied to the warming climate and resulting changes in sea ice and nutrient dynamics. The development of the Coastal Synchrony Index (CSI) provided a novel metric for comparing productivity changes and illustrated the interconnected nature of terrestrial and marine environments. At lower latitudes, the study of major watersheds highlighted the significant impact of human activities on land productivity and the subsequent effects on coastal marine ecosystems. These studies underscore the complex linkages between land and ocean, reinforcing the need for integrated land-ocean models in predicting and managing the effects of climate change on Earth’s biogeochemical cycles. While the immediate application of these findings to socioeconomic strategies and coastal management are beyond the scope of this thesis, they do provide a scientific foundation of the land-ocean coupling information that can be assimilated and tested in climate models. Overall, this thesis reaffirms the importance of studying land and ocean as interconnected systems, recognizing the profound and cascading impacts of human activities on the carbon cycle on these critical fringes.