Abstract
The Arctic is one of the regions in our planet with strongest warming
observed and it is also almost certain to continue to change in the near
future. The continuous change in key indicators of Arctic climate change
(e.g. increase of temperature, intensification of the hydrological
cycle, and shortening of the spring snow cover) will have marked
consequences on ecosystem carbon (C) sink-source functioning. Such
consequences are, however, broadly uncertain. Comprehensively integrated
ecosystem models with long-term in-situ data are essential to understand
the Arctic C cycle sensitivity to climate change and explore robust
future scenarios. Our aim is to quantify the relative sensitivity of
Greenland’s C balance to climate change based on regional variation in C
and N cycling in a tundra gradient. The key roadblocks to this
understanding have been limited time series of C fluxes, and limited
regional data. Now with observations from multiple data streams measured
by the Greenland Ecosystem Monitoring (GEM) program over the last two
decades in conjunction with proven ecosystem and climate models we 1)
analyse the underlying processes and links between present climate and
terrestrial C and N cycling and 2) forecast the variation of plant
phenology, productivity, and respiration forward in time. We use an
established but novel C cycle model, the Soil-Plant-Atmosphere model,
applied to two GEM wetlands relying on previous substantiated efforts on
source-code model implementation, model calibration, and validation
based on quality-controlled long-term data. Additionally, our modelling
framework is now forced with future projections from the regional
climate model HIRHAM5 specifically designed to characterize the
Greenland domain (typically left behind in global modelling analyses)
following the IPCC greenhouse gas emission scenarios. We ask the
ecological question: How sensitive is the C balance expected to be under
warmer and wetter conditions forecasted for the 21st century? Although
still preliminary, we found strong evidence that the net C exchange will
be significantly exposed to higher temperatures and intensified
precipitation levels increasing 10-80% the C sink strength by the end
of the century, but lengthening of the growing season and nutrient
availability will also play a significant role.