Abstract
Abstract. Polar amplification – the phenomenon where external radiative forcing produces a larger change in surface temperature at high latitudes than the global average – is a key aspect of anthropogenic climate change, but its causes and consequences are not fully understood. The Polar Amplification Model Intercomparison Project (PAMIP) contribution to the sixth Coupled Model Intercomparison Project (CMIP6; Eyring et al., 2016) seeks to improve our understanding of this phenomenon through a coordinated set of numerical model experiments documented here. In particular, PAMIP will address the following primary questions: (1) what are the relative roles of local sea ice and remote sea surface temperature changes in driving polar amplification? (2) How does the global climate system respond to changes in Arctic and Antarctic sea ice? These issues will be addressed with multi-model simulations that are forced with different combinations of sea ice and/or sea surface temperatures representing present-day, pre-industrial and future conditions. The use of three time periods allows the signals of interest to be diagnosed in multiple ways. Lower-priority tier experiments are proposed to investigate additional aspects and provide further understanding of the physical processes. These experiments will address the following specific questions: what role does ocean–atmosphere coupling play in the response to sea ice? How and why does the atmospheric response to Arctic sea ice depend on the pattern of sea ice forcing? How and why does the atmospheric response to Arctic sea ice depend on the model background state? What have been the roles of local sea ice and remote sea surface temperature in polar amplification, and the response to sea ice, over the recent period since 1979? How does the response to sea ice evolve on decadal and longer timescales? A key goal of PAMIP is to determine the real-world situation using imperfect climate models. Although the experiments proposed here form a coordinated set, we anticipate a large spread across models. However, this spread will be exploited by seeking “emergent constraints” in which model uncertainty may be reduced by using an observable quantity that physically explains the intermodel spread. In summary, PAMIP will improve our understanding of the physical processes that drive polar amplification and its global climate impacts, thereby reducing the uncertainties in future projections and predictions of climate change and variability.
Highlights
Polar amplification refers to the phenomenon in which zonally averaged surface temperature changes in response to climate forcings are larger at high latitudes than the global average
Antarctic amplification is expected in the future in response to further increases in greenhouse gases but is likely to be delayed relative to the Arctic due to strong heat uptake in the Southern Ocean (Collins et al, 2013; Armour et al, 2016)
What are the relative roles of local sea ice and remote sea surface temperature changes in driving polar amplification, and how does the global climate system respond to changes in Arctic and Antarctic sea ice? This set contains all of the tier 1 experiments and provides a multi-model assessment of the primary scientific questions addressed by Polar Amplification Model Intercomparison Project (PAMIP)
Summary
Polar amplification refers to the phenomenon in which zonally averaged surface temperature changes in response to climate forcings are larger at high latitudes than the global average. Especially in the Arctic, is a robust feature of global climate model simulations of recent decades (Bindoff et al, 2013) and future projections driven by anthropogenic emissions of carbon dioxide (Fig. 1, Collins et al, 2013). The Polar Amplification Model Intercomparison Project (PAMIP) will investigate the causes and global consequences of polar amplification, through creation and analysis of an unprecedented set of coordinated multi-model experiments and strengthened international collaboration. – provide new multi-model estimates of the global climate response to Arctic and Antarctic sea ice changes;. This will be addressed through coordinated multi-model experiments to understand the causes and consequences of polar amplification.
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