Organic matter in Arctic Rivers
Remote SEnsing of DOM
Colored dissolved organic matter (CDOM) is a useful proxy for dissolved organic carbon in Arctic rivers, an important part of the carbon cycle and source of energy and nutrients to aquatic and estuarine microbes. I built remote sensing models for six large Arctic rivers to estimate CDOM (Griffin et al., 2018a), then applied those models to historical imagery from 1985 - 2017 (Griffin, 2016). Time series analyses showed increased discharge-normalized CDOM in the Ob' River, where warming likely led to DOM mobilization from extensive peatlands. The adjacent Yenisey River, in contrast, decreased in discharge-normalized CDOM. The Yenisey lacks the deep, extensive peatlands on the Ob', and as permafrost thawed, hydrological flowpaths deepened and flowed through more mineral soils.
River export of OM
I have been lucky to be involved with the Arctic Great Rivers Observatory, which provided the data used for my remote sensing methods. Methodologically-consistent, seasonally explicit sampling of large river mouths allows researchers to quantify how much terrestrial material enters the Arctic Ocean, and use biogeochemical signals as indicators of widespread change throughout a watershed. Through Arctic-GRO, I have contributed to work on fluxes of particulate organic matter (POM), addressing the variability in export driven by both seasonal and annual hydrology (McClelland et al., 2016). Organic matter in Arctic rivers generally increases in age by the end of the ice-free season. Radiocarbon dating of lignins demonstrated that such ancient pools of carbon are far more prevalent in the Kolyma River than the Mackenzie River (Feng et al., 2017).