LETTERS Persistence of full glacial conditions in the central Pacific until 15,000 years ago P.-H. Blard 1,2 {, J. Lave ´ 3 {, R. Pik 2 , P. Wagnon 4 & D. Bourle `s 1 The magnitude of atmospheric cooling during the Last Glacial Maximum and the timing of the transition into the current inter- glacial period remain poorly constrained in tropical regions, partly because of a lack of suitable climate records 1 . Glacial mor- aines provide a method of reconstructing past temperatures, but they are relatively rare in the tropics. Here we present a recon- struction of atmospheric temperatures in the central Pacific dur- ing the last deglaciation on the basis of cosmogenic 3 He ages of moraines and numerical modelling of the ice cap on Mauna Kea volcano, Hawaii—the only highland in the central Pacific on which moraines that formed during the last glacial period are preserved 2 . Our reconstruction indicates that the Last Glacial Maximum occurred between 19,000 and 16,000 years ago in this region and that temperatures at high elevations were about 7 6C lower than today during this interval. Glacial retreat began about 16,000 years ago, but temperatures were still about 6.5 6C lower than today until 15,000 years ago. When combined with estimates of sea surface temperatures in the central Pacific Ocean 3 , our reconstruction indicates that the lapse rate during the Last Glacial Maximum was higher than at present, which is consistent with the proposal that the atmosphere was drier at that time 1,4 . Furthermore, the persistence of full glacial conditions until 15,000 years ago is consistent with the relatively late and abrupt tran- sition to warmer temperatures in Greenland 5 , indicating that there may have been an atmospheric teleconnection between the central Pacific and North Atlantic regions during the last deglaciation. There is an important need for precise ice-retreat chronology in areas where past glaciers are the sole indicators of palaeoclimate. Mauna Kea volcano (elevation 4,206 m) is the only highland area of the central Pacific (Hawaii, 19u N) where moraines of the last glaciation have been preserved 2 (Fig. 1). Fortunately, many of the glacial deposits on Mauna Kea are not covered by volcanic material and have been exposed continuously since their formation. The emplacement of these moraines can therefore be dated by using cosmic-ray exposure methods. This late Pleistocene glacial footprint is represented by a ,10-km diameter cap of moraines draping the upper slopes of the volcano. These deposits extend downslope to a mean elevation of 3,400–3,500 m, with local outlet digitations reaching altitudes as low as 3,200 m in places such as the Pohakuloa gulch (Fig. 1c). The age of these glacial deposits has been 1 Centre Europe ´en de Recherche et d’Enseignement des Ge ´osciences de l’Environnement, CNRS – Aix Marseille Universite ´, 13545 Aix en Provence, France. 2 Centre de Recherches Pe ´trographiques et Ge ´ochimiques, CNRS, 54501 Vandoeuvre-le `s-Nancy, France. 3 Laboratoire de Ge ´odynamique des Chaı ˆnes Alpines, CNRS – Universite ´ Joseph Fourier, 38400 Grenoble, France. 4 Institut de Recherche Pour le De ´veloppement, Great Ice, Laboratoire de Glaciologie et Ge ´ophysique de l’Environnement, 38402 Grenoble, France. {Present addresses: Geological and Planetary Science Division, California Institute of Technology, MC 100-23, 1200 E. California Boulevard, Pasadena, California 91125, USA (P.-H.B.); Centre de Recherches Pe ´trographiques et Ge ´ochimiques, CNRS, 54501 Vandoeuvre-le`s-Nancy, France (J.L.). 500 m Pohakuloa Gulch Pohakuloa Gulch M0 M1 M2a c MK12 MK9 MK10 Mauna Kea Mauna Kea b M2b LW N 180° –150°–120° –90° 150° 120° 45° 30° 0° –30° –45° Hawaii Pacific Ocean 60° a MK11 Makanaka moraines M2c –155° 30′ 19° 47′ –155° 29.5′ 19° 47.5′ 5 km Figure 1 | Map of the sampled glacial deposits (Mauna Kea, Hawaii, central Pacific). a, Location of the Hawaiian Islands in the Pacific Ocean. The square shows the location of marine core MD02-2503, Santa Barbara Basin 27 . b, Location of the Pohakuloa gulch (SPOT image). LW, Lake Waiau. c, Map of moraines extents (M0 in orange, M1 in red, M2a, M2b and M2c in blue) and locations of the sampled boulders. Vol 449 | 4 October 2007 | doi:10.1038/nature06142 591 Nature ©2007 Publishing Group