Is arctic greening consistent with the ecology of tundra? Lessons from an ecologically informed mass balance model

Abstract

Climate change has been implicated in the widespread 'greening' of the arctic in recent decades. However, differences in arctic greening patterns among satellite platforms and recent reports of decreased rate of greening or of browning have made attributing arctic greening trends to a warming climate challenging. Here, we compared MODIS greening trends to those predicted by the coupled carbon and nitrogen model (CCaN); a mass balance carbon and nitrogen model that was driven by MODIS surface temperature and climate. CCaN was parameterized using model-data fusion, where model predictions were ecologically constrained with historical ecological ground and satellite based data. We found that, at long temporal and large spatial scales, MODIS greening trends were consistent with ecological and biogeochemical data from arctic tundra. However, at smaller spatial scales, observations and CCaN greening trends differed in the location, extent, and magnitude of greening. CCaN was unable to capture the high rates of MODIS greening in northern wetlands, and the patchy MODIS browning in the southern portion of the North Slope. This model-data disagreement points to disturbance and its legacy impacts on land cover as an important mechanism for understanding greening trends on the North Slope of Alaska.