Reconstruction of Past Antarctic Temperature Using Present Seasonal d18O-Inversion Layer Temperature: Unified Slope Equations and Applications

Reconstructing the history of polar temperature from ice core water isotope (618O) calibration has remained a challenge in paleoclimate research, because of our incomplete understanding of various temperature-618O relationships. This paper resolves this classical problem in a new framework called the unified slope equations (USE), which illustrates the general relations among spatial and temporal 618O-surface temperature slopes. The USE is applied to the Antarctica temper-ature change during the last deglaciation in model simulations and observations. It is shown that the comparable Antarctica -mean spatial slope with deglacial temporal slope in 618O-surface temperature reconstruction is caused, accidentally, by the compensation responses between the 618O-inversion layer temperature relation and the inversion layer temperature itself. Furthermore, in light of the USE, we propose that the present seasonal slope of 618O-inversion layer temperature is an opti-mal paleothermometer that is more accurate and robust than the spatial slope. This optimal slope suggests the possibility of reconstructing past Antarctic temperature changes using present and future instrumental observations.