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A high resolution (0.05 m) water isotopic record ($\delta^{18}\mathrm{O}$) isavailable from the NorthGRIP ice core. In this study we look into the waterisotope diffusion history as estimated by the spectral characteristics of the$\delta^{18}\mathrm{O}$ time series covering the last 16,000 years. Thediffusion of water vapor in the porous medium of the firn pack attenuates theinitial isotopic signal, predominantly having an impact on the high frequencycomponents of the power spectrum. Higher temperatures induce higher rates ofsmoothing and thus the signal can be used as a firn paleothermometer. We use awater isotope diffusion model coupled to a steady-state densification model inorder to infer the temperature signal from the site, assuming the accumulationand strain rate history as estimated using the GICC05 layer counted chronologyand a Dansgaard--Johnsen ice flow model. The temperature reconstructionaccurately captures the timing and magnitude of the B{\o}lling--Aller{\o}d andYounger Dryas transitions. A Holocene climatic optimum is seen between 7 and 9ky b2k with an apparent cooling trend thereafter. Our temperature estimate forthe Holocene climatic optimum, points to a necessary adjustment of the icethinning function indicating that the ice flow model overestimates pastaccumulation rates by about 10\% at 8 ky b2k. Finally, the record presents aclimatic variability over the Holocene spanning millennial and centennialscales with a profound cooling occurring at approximately 4000 years b2k. Thenew reconstruction technique is able to provide past temperature estimates byovercoming the issues apparent in the use of the classical$\delta^{18}\mathrm{O}$ slope method. It can in the same time resolvetemperature signals at low and high frequencies.

Water isotope diffusion rates from the NorthGRIP ice core for the last 16,000 years - glaciological and paleoclimatic implications