Journal Article

Sensitivity of atmospheric CO2 growth rate to observed changes in terrestrial water storage

Zscheischler, Jakob, Sitch, Stephen, Seneviratne, Sonia I., Gudmundsson, Lukas, Ciais, Philippe, Humphrey, Vincent

2018

Overview

Land ecosystems absorb on average 30 per cent of anthropogenic carbon dioxide (CO 2 ) emissions, thereby slowing the increase of CO 2 concentration in the atmosphere 1 . Year-to-year variations in the atmospheric CO 2 growth rate are mostly due to fluctuating carbon uptake by land ecosystems 1 . The sensitivity of these fluctuations to changes in tropical temperature has been well documented 2 – 6 , but identifying the role of global water availability has proved to be elusive. So far, the only usable proxies for water availability have been time-lagged precipitation anomalies and drought indices 3 – 5 , owing to a lack of direct observations. Here, we use recent observations of terrestrial water storage changes derived from satellite gravimetry 7 to investigate terrestrial water effects on carbon cycle variability at global to regional scales. We show that the CO 2 growth rate is strongly sensitive to observed changes in terrestrial water storage, drier years being associated with faster atmospheric CO 2 growth. We demonstrate that this global relationship is independent of known temperature effects and is underestimated in current carbon cycle models. Our results indicate that interannual fluctuations in terrestrial water storage strongly affect the terrestrial carbon sink and highlight the importance of the interactions between the water and carbon cycles. The growth rate of global atmospheric CO 2 concentration is faster in drier years, independently of temperature; this relationship is underestimated in current carbon cycle models.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 704/106/242 / 704/47/4113 / Anthropogenic factors / Atmospheric models / Carbon / Carbon cycle / Carbon cycle models / Carbon dioxide / Carbon dioxide atmospheric concentrations / Carbon dioxide concentration / Carbon dioxide emissions / Carbon sinks / Carbon uptake / Climate change / Continental interfaces, environment / Drought / Ecosystems / Estimates / Fluctuations / Gravimetry / Growth rate / Humanities and Social Sciences / Hydrology / Letter / multidisciplinary / Ocean, Atmosphere / Precipitation / Precipitation anomalies / Reservoirs / Science / Science (multidisciplinary) / Sciences of the Universe / Sensitivity / Temperature effects / Terrestrial environments / Trends / Water availability / Water shortages / Water storage