Search for: All records

Abstract. Over the past 0.8 million years, 100kyr ice ages have dominatedEarth's climate with geological evidence suggesting the last glacialinception began in the mountains of Baffin Island. Currently,state-of-the-art global climate models (GCMs) have difficulty simulatingglacial inception, possibly due in part to their coarse horizontal resolutionand the neglect of ice flow dynamics in some models. We attempt to addressthe role of regional feedbacks in the initial inception problem on BaffinIsland by asynchronously coupling the Weather Research and Forecast (WRF) model,configured as a high-resolution inner domain over Baffin and an outerdomain incorporating much of North America, to an ice flow model using theshallow ice approximation. The mass balance is calculated from WRFsimulations and used to drive the ice model, which updates the ice extentand elevation, that then serve as inputs to the next WRF run. We drive theregional WRF configuration using atmospheric boundary conditions from 1986that correspond to a relatively cold summer, and with 115kya insolation.Initially, ice accumulates on mountain glaciers, driving downslope ice flowwhich expands the size of the ice caps. However, continued iterations of theatmosphere and ice models reveal a stagnation of the ice sheet on BaffinIsland, driven by melting due to warmer temperatures at the margins of theice caps. This warming is caused by changes in the regional circulation thatare forced by elevation changes due to the ice growth. A stabilizing feedbackbetween ice elevation and atmospheric circulation thus prevents fullinception from occurring.

Arctic‐boreal landscapes are experiencing profound warming, along with changes in ecosystem moisture status and disturbance from fire. This region is of global importance in terms of carbon feedbacks to climate, yet the sign (sink or source) and magnitude of the Arctic‐boreal carbon budget within recent years remains highly uncertain. Here, we provide new estimates of recent (2003–2015) vegetation gross primary productivity (GPP), ecosystem respiration (R_eco), net ecosystem CO₂exchange (NEE;R_eco − GPP), and terrestrial methane (CH₄) emissions for the Arctic‐boreal zone using a satellite data‐driven process‐model for northern ecosystems (TCFM‐Arctic), calibrated and evaluated using measurements from >60 tower eddy covariance (EC) sites. We used TCFM‐Arctic to obtain daily 1‐km²flux estimates and annual carbon budgets for the pan‐Arctic‐boreal region. Across the domain, the model indicated an overall average NEE sink of −850 Tg CO₂‐C year⁻¹. Eurasian boreal zones, especially those in Siberia, contributed to a majority of the net sink. In contrast, the tundra biome was relatively carbon neutral (ranging from small sink to source). Regional CH₄emissions from tundra and boreal wetlands (not accounting for aquatic CH₄) were estimated at 35 Tg CH₄‐C year⁻¹. Accounting for additional emissions from open water aquatic bodies and from fire, using available estimates from the literature, reduced the total regional NEE sink by 21% and shifted many far northern tundra landscapes, and some boreal forests, to a net carbon source. This assessment, based on in situ observations and models, improves our understanding of the high‐latitude carbon status and also indicates a continued need for integrated site‐to‐regional assessments to monitor the vulnerability of these ecosystems to climate change.