A sea ice-free Arctic during the Last Interglacial supports fast future loss

Abstract

<p>The Last Interglacial (LIG) is a period of great importance as an analog for future climate change. Global sea level was 6-9 m higher than present. Stronger LIG summertime insolation at high northern latitudes drove Arctic land summer temperatures around 4-5 K higher than during the preindustrial era. Climate-model simulations have previously failed to capture these elevated temperatures. This may be because these models failed to correctly capture LIG sea ice changes.</p><p>Here, we show that the latest version of the UK Hadley Center coupled ocean-atmosphere climate model (HadGEM3) simulates a much improved Arctic LIG climate, including the observed high temperatures. Improved model physics in HadGEM3, including a sophisticated sea ice melt-pond scheme, results in the first-ever simulation of the complete loss of Arctic sea ice in summer during the LIG.</p><p>Our ice-free Arctic yields a compelling solution to the long-standing puzzle of what drove LIG Arctic warmth. The LIG simulation result is a new independent constraint on the strength of Arctic sea ice decline in climate-model projections, and provides support for a fast retreat of Arctic summer sea ice in the future.</p>

Biases Beyond the Mean in CMIP6 Extreme Precipitation: A Global Investigation

“…This dry bias in the Tropics was also confirmed in the literature using CMIP6 multi‐model means (Kim et al., 2020). Generally, the literature indicates that climate models perform poorly in tropical and Arctic Regions (Cesana & Del Genio, 2021; Guarino et al., 2020; Wunderling et al., 2020). Nevertheless, NorCPM1, MIROC6, and CanESM5 have of median approaching zero in Arctic, North temperate, and Tropics and South temperate regions, respectively.…”

“…CMIP6 models show large variability in the Arctic and Tropics and also differ from the observations when compared in terms of L‐moments. This poor performance, in the Arctic, could be attributed to inadequate stimulation of sea‐ice interactions that affect the models' results globally and locally (Guarino et al., 2020; Jansen et al., 2020). When ice melts, the albedo decreases which has feedback to the land‐atmosphere processes.…”

“…When ice melts, the albedo decreases which has feedback to the land‐atmosphere processes. Precise integration of sea‐ice interactions is expected to improve climate modeling (Guarino et al., 2020; Rosenblum & Eisenman, 2017). Additionally, warming rates in these frozen regions are at least double the global rates and are not represented accurately (Jansen et al., 2020).…”

A Comparison of the CMIP6midHoloceneandlig127kSimulations in CESM2

“…CESM2 has a high equilibrium climate sensitivity (ECS) of 5.3 °C (Gettelman et al, 2019); HadGEM3 similarly has a high ECS of 5.5 °C. Both predict an almost ice‐free or ice‐free Arctic in their lig127k experiments and the predicted year of disappearance of September sea ice in the SSP8–8.5 scenario of 2038 and 2035, respectively (Guarino et al, 2020). The CMIP6 and PMIP4 paleoclimate simulations with CESM2 combined with proxy reconstructions allow an assessment of whether this high ECS is plausible (Feng et al, 2020; Zhu et al, 2020).…”

The Role of Conservation Biology in Understanding the Importance of Arctic Sea Ice

“…Decreasing sea ice cover, not changes in terrestrial snow cover, has been the dominant radiative feedback mechanism during the last few decades [9]. Furthermore, a 2020 simulation result "provides support for a fast retreat of Arctic summer sea ice in the future" [10].…”