Abstract
Abstract. There remain substantial uncertainties in future projections of Arctic climate change. There is a potential to constrain these uncertainties using a combination of paleoclimate simulations and proxy data, but such a constraint must be accompanied by physical understanding on the connection between past and future simulations. Here, we examine the relevance of an Arctic warming mechanism in the mid-Holocene (MH) to the future with emphasis on process understanding. We conducted a surface energy balance analysis on 10 atmosphere and ocean general circulation models under the MH and future Representative Concentration Pathway (RCP) 4.5 scenario forcings. It is found that many of the dominant processes that amplify Arctic warming over the ocean from late autumn to early winter are common between the two periods, despite the difference in the source of the forcing (insolation vs. greenhouse gases). The positive albedo feedback in summer results in an increase in oceanic heat release in the colder season when the atmospheric stratification is strong, and an increased greenhouse effect from clouds helps amplify the warming during the season with small insolation. The seasonal progress was elucidated by the decomposition of the factors associated with sea surface temperature, ice concentration, and ice surface temperature changes. We also quantified the contribution of individual components to the inter-model variance in the surface temperature changes. The downward clear-sky longwave radiation is one of major contributors to the model spread throughout the year. Other controlling terms for the model spread vary with the season, but they are similar between the MH and the future in each season. This result suggests that the MH Arctic change may not be analogous to the future in some seasons when the temperature response differs, but it is still useful to constrain the model spread in the future Arctic projection. The cross-model correlation suggests that the feedbacks in preceding seasons should not be overlooked when determining constraints, particularly summer sea ice cover for the constraint of autumn–winter surface temperature response.
Highlights
The magnitude of climate change has been shown to be larger at high latitudes with paleoclimate evidence (MassonDelmotte et al, 2006, 2013) and climate model equilibrium simulations (Manabe and Wetherald, 1975; Stouffer and Manabe, 1999)
The current study focuses on the mid-Holocene partly because multi-model simulations for this period are accessible through the CMIP5 data archive, and the compiled reconstruction dataset is available
The insolation in the Arctic region decreases in autumn for the MH relative to the modern period, the largest MH Arctic warming occurs in autumn
Summary
The magnitude of climate change has been shown to be larger at high latitudes with paleoclimate evidence (MassonDelmotte et al, 2006, 2013) and climate model equilibrium simulations (Manabe and Wetherald, 1975; Stouffer and Manabe, 1999). A much slower rate of warming occurs in the Southern Ocean primarily due to oceanic processes (Armour et al, 2016), it is possible that stratospheric ozone change and cloud feedback play additional roles (Marshall et al, 2014; Yoshimori et al, 2017). A substantial part of the uncertainty in the future Arctic warming projections is attributed to the differences among numerical models (Hodson et al, 2013). The projected range of future Arctic warming within each Representative Concentration Pathway (RCP) scenario is much larger than that for the global mean. The 90 % confidence interval for the annual mean surface air temperature (SAT) change from the late 20th century to the late 21st century for the Arctic mean (67.5–90◦ N) is estimated
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