Rapid Communication: Two-phase Arctic cryosphere patterns associated with delayed Norwegian Sea warming peak during the Last Interglacial

Abstract. The Last Interglacial (LIG; ~129–117 ka), when global temperatures were comparable to today, provides a valuable testbed for understanding how Arctic cryosphere–ocean interactions may shape regional climate responses. By synthesizing multiproxy records from the Norwegian Sea, North Atlantic, and Southern Ocean, we identify two previously unrecognized phases of delayed Norwegian Sea warming during the early LIG. Phase I (~129–128 ka) was marked by widespread winter sea ice and freshwater input from the retreating Eurasian ice sheets, and was likely associated with large-scale reorganizations of the Atlantic Meridional Overturning Circulation (AMOC). Phase II (during 128–124 ka) featured a localized delay in Norwegian Sea warming peak, likely associated with enhanced Arctic sea-ice melt and freshwater export rather than residual deglacial meltwater. This two-phase framework suggests that sea ice-driven feedbacks, rather than lingering Eurasian ice sheets, were linked to the Phase II delay. Importantly, Phase II does not necessarily imply a synchronous central Arctic cooling, and may instead reflect a localized “warming hole” in the Norwegian Sea. These findings refine the context for the 127 ka Coupled Model Intercomparison Project (CMIP) paleoclimate simulations and further highlight the potential role of Arctic sea ice dynamics in modulating the AMOC and subpolar climate anomalies.