The nonlinear and distinct responses of ocean heat content and
anthropogenic carbon to ice sheet freshwater discharge in a warming
climate
Abstract
Anthropogenic climate change will drive extensive mass loss across both
the Antarctic (AIS) and Greenland Ice Sheets (GrIS), with the potential
for feedbacks on the global climate system, especially in polar regions.
Historically, the high latitude North Atlantic and Southern Ocean have
been the most critical regions for global anthropogenic heat and carbon
uptake, but our understanding of how this uptake will be altered by
future freshwater discharge is incomplete. Here, we assess each ice
sheet’s impact on the global ocean storage of anthropogenic heat and
carbon for a high-emission scenario over the
21$^{\textrm{st}}$ century using a coupled Earth
system model. Notably, combined AIS and GrIS freshwater engenders
distinct anthropogenic heat and carbon storage anomalies as the two
diagnostics respond disparately in the high latitude Southern Ocean and
North Atlantic. We explore the impact of contemporaneous mass loss from
both ice sheets on anthropogenic heat and carbon storage and quantify
the linear and nonlinear contributions of each ice sheet. We find that
GrIS mass loss exerts a primary control on the 21$^{st}$-century
evolution of both global oceanic heat and carbon storage, with AIS
impacts appearing after the 2080s. Non-linear impacts of simultaneous
ice sheets’ discharge have a non-negligible contribution to the
evolution of both heat and carbon storage. Further, anthropogenic heat
changes are realized more quickly in response to ice sheet discharge
than anthropogenic carbon. Our results highlight the need to incorporate
both ice sheets actively in climate models in order to accurately
project future global climate.