Antarctic Ice‐Sheet Meltwater Reduces Transient Warming and Climate Sensitivity Through the Sea‐Surface Temperature Pattern Effect. Issue 24 (14th December 2022)

• Record Type: Journal Article
• Authors: Dong, Yue; Pauling, Andrew G.; Sadai, Shaina; Armour, Kyle C.
• Is Part Of: Geophysical research letters. Volume 49:Issue 24(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-14
• Subjects: climate sensitivity -- Antarctic meltwater -- climate models -- Southern Ocean teleconnections -- cloud feedbacks; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL101249
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Coupled global climate models (GCMs) generally fail to reproduce the observed sea‐surface temperature (SST) trend pattern since the 1980s. The model‐observation discrepancies may arise in part from the lack of realistic Antarctic ice‐sheet meltwater input in GCMs. Here we employ two sets of CESM1‐CAM5 simulations forced by anomalous Antarctic meltwater fluxes over 1980–2013 and through the 21st century. Both show a reduced global warming rate and an SST trend pattern that better resembles observations. The meltwater drives surface cooling in the Southern Ocean and the tropical southeast Pacific, in turn increasing low‐cloud cover and driving radiative feedbacks to become more stabilizing (corresponding to a lower effective climate sensitivity). These feedback changes can contribute as substantially as ocean heat uptake efficiency changes in reducing the global warming rate. Accurately projecting historical and future warming thus requires improved representation of Antarctic meltwater and its impacts. Plain Language Summary: Observations have shown surface cooling in the Southern Ocean and the tropical southeast Pacific over the last four decades. However, global climate models generally struggle to reproduce this pattern. The model‐observation mismatch has been proposed to partly arise from the fact that models lack in representation of realistic Antarctic ice‐sheet meltwater input to the Southern Ocean. Here we revisit two sets of simulations with meltwater fluxes and examine the impact of meltwater input on global warming and the global energy budget. We find that accounting for meltwater input slows global warming and produces a surface warming pattern closer to recent observations. The reduced global warming rate is caused by both more efficient ocean heat uptake and stronger radiative feedbacks (more efficient radiative damping to space) that are associated with changes in the surface warming pattern. These results indicate a critical impact of Antarctic meltwater on the global climate that has been missed in current climate models. Key Points: Accounting for Antarctic meltwater input in a global climate model reduces the global warming rate and produces a warming pattern closer to the observed Antarctic meltwater impacts not only the Southern Ocean, but also the tropics via teleconnections The reduced global warming rate is driven by changes in both ocean heat uptake efficiency and radiative feedbacks