Decadal trends in the release of terrigenous organic carbon to the Mackenzie Delta (Canadian Arctic) using satellite ocean color data (1998–2019)

Abstract

Arctic rivers operate as integrators of northern high latitude regions, where large stocks of soil organic carbon (OC) are currently experiencing rapid warming. Here we show that tracking total OC in the Mackenzie Delta whose upstream catchment is underlain by permafrost soils is now possible using polar-orbiting satellite ocean color observations. A non-parametric trend analysis that is valid for hydrological data shows a significant increase in dissolved OC (DOC) as well as particulate OC (POC) concentrations in late summer (0.019 and 0.069 g m−3 year−1; p < 0.05 for both). Uncertainties of the satellite estimates of DOC and POC do not influence our results. These concentration increases are not related to changes in river discharge. Parallel increases of independent long-term (1979–2018) in situ measurements of thaw depth of the active layer, as well as meteorological and hydrological patterns suggest that these late summer increases can likely be explained by increasing inputs of permafrost OC. This study shows great promise for remote, large-scale detection of catchment-scale thaw impacts from space.