Glacial Warming in the Eastern Pacific Warm Pool

The Eastern Pacific Warm Pool (EPWP) modulates global climate through its connection with tropical Pacific circulation, but sparse paleoceanographic data from this region limits our understanding of its role in past climate variability. We present a 144 kyr alkenone‐sea surface temperature (SST) reconstruction from core NH22P, located in the northern EPWP, that shows local warming occurred during periods of global cooling. Climate model simulations of the Last Glacial Maximum indicate that both ice sheet and greenhouse gas forcing slowed wind speeds over the EPWP, which attenuated glacial cooling of local SST via the wind‐evaporation‐SST feedback. Spectral analysis further suggests precessional pacing of the warming spikes. Vernal equinox insolation could explain this pacing as direct shortwave heating during boreal spring would have contributed to the early seasonal intensification of the EPWP. This work provides crucial constraints on tropical Pacific glacial climate variability and highlights the unique response of the EPWP to global climate forcings. Plain Language Summary The eastern tropical Pacific (ETP) contains a region of very warm sea surface temperatures (SSTs) (>27.5°C) that is called the Eastern Pacific Warm Pool (EPWP). The interaction between these warm waters and the atmosphere is important for driving rainfall variability in Mexico and Central America. Our understanding of SST variability in the EPWP in the past, however, is limited by a lack of paleoceanographic data. In this study, we present a new record of past changes in EPWP SST based on abundances of algal lipids called alkenones. We use climate models to understand how lower greenhouse gases and increased ice volume affected SST in the EPWP and atmospheric circulation in the ETP. We find that both of these factors result in less evaporation from the EPWP, which limits the amount of cooling the region underwent despite widespread global cooling during the last ice age. Regular intervals of warming occur when radiation from the Sun reaching Earth's surface in Northern Hemisphere spring is greatest as cloud cover over the EPWP is low at this time and warming of the sea surface is enhanced. Key Points A new reconstruction from the northern Eastern Pacific Warm Pool (EPWP) shows warming during globally cool periods over the last ∼150 kyrs Reduced wind‐evaporation‐sea surface temperature feedback key for attenuating glacial cooling in the EPWP Precessional pacing of EPWP sea surface tem