Contrasting regional carbon cycle responses to seasonal climate
anomalies across the east-west divide of temperate North America
Abstract
Across temperate North America, interannual variability (IAV) in gross
primary production (GPP) and net ecosystem exchange (NEE), and their
relationship with environmental drivers, are poorly understood. Here, we
examine IAV in GPP and NEE and their relationship to environmental
drivers using two state-of-the-science flux products: NEE constrained by
surface and space-based atmospheric CO2 measurements over 2010–2015 and
satellite up-scaled GPP from FluxSat over 2001-2017. We show that the
arid western half of temperate North America provides a larger
contribution to IAV in GPP (104% of east) and NEE (127% of east) than
the eastern half, in spite of smaller magnitude of annual mean GPP and
NEE. This occurs because anomalies in western ecosystems are temporally
coherent across the growing season leading to an amplification of GPP
and NEE. In contrast, IAV in GPP and NEE in eastern ecosystems are
dominated by seasonal compensation effects, associated with opposite
responses to temperature anomalies in spring and summer. Terrestrial
biosphere models in the MsTMIP ensemble generally capture these
differences between eastern and western temperate North America,
although there is considerable spread between models.