title: Surface-atmosphere decoupling limits accumulation at Summit, Greenland.
abstract: Despite rapid melting in the coastal regions of the Greenland Ice Sheet, a significant area (~40%) of the ice sheet rarely experiences surface melting. In these regions, the controls on annual accumulation are poorly constrained owing to surface conditions (for example, surface clouds, blowing snow, and surface inversions), which render moisture flux estimates from myriad approaches (that is, eddy covariance, remote sensing, and direct observations) highly uncertain. Accumulation is partially determined by the temperature dependence of saturation vapor pressure, which influences the maximum humidity of air parcels reaching the ice sheet interior. However, independent proxies for surface temperature and accumulation from ice cores show that the response of accumulation to temperature is variable and not generally consistent with a purely thermodynamic control. Using three years of stable water vapor isotope profiles from a high altitude site on the Greenland Ice Sheet, we show that as the boundary layer becomes increasingly stable, a decoupling between the ice sheet and atmosphere occurs. The limited interaction between the ice sheet surface and free tropospheric air reduces the capacity for surface condensation to achieve the rate set by the humidity of the air parcels reaching interior Greenland. The isolation of the surface also acts to recycle sublimated moisture by recondensing it onto fog particles, which returns the moisture back to the surface through gravitational settling. The observations highlight a unique mechanism by which ice sheet mass is conserved, which has implications for understanding both past and future changes in accumulation rate and the isotopic signal in ice cores from Greenland.
authors.affiliation: Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA.; Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.; Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO 80309, USA.
authors.forename: Max
authors.initials: M
authors.lastname: Berkelhammer
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.; Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO 80309, USA.; College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Noone
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.; Laboratoire des Sciences du Climat et de l'Environnement, UMR CEA-CNRS-UVSQ/IPSL 8212, Gif-sur-Yvette, France.; Center for Ice and Climate, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Hans Christian
authors.initials: HC
authors.lastname: Steen-Larsen
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.; Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO 80309, USA.; Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, WA 98195, USA.
authors.forename: Adriana
authors.identifier: 0000-0002-2614-1560
authors.initials: A
authors.lastname: Bailey
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.; Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO 80309, USA.; National Oceanic and Atmospheric Administration, Boulder, CO 80305, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Cox
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.; National Oceanic and Atmospheric Administration, Boulder, CO 80305, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: O'Neill
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.; National Center for Atmospheric Research, Boulder, CO 80305, USA.
authors.forename: David
authors.initials: D
authors.lastname: Schneider
authors.affiliation: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309, USA.; Swiss Federal Research Institute WSL, Birmensdorf, Switzerland.
authors.forename: Konrad
authors.identifier: 0000-0001-8658-1026
authors.initials: K
authors.lastname: Steffen
authors.affiliation: Department of Geological Sciences, University of Colorado, Boulder, CO 80309, USA.; Environmental Studies Program, University of Colorado, Boulder, CO 80309, USA.; Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA.
authors.forename: James W C
authors.initials: JW
authors.lastname: White
mesh_terms: D001272:Atmosphere; D005615:Freezing; D057232:Global Warming; D006116:Greenland; D046448:Ice Cover; D012914:Snow; D013696:Temperature; D014872:Water Movements
keywords: Greenland Ice sheet; atmospheric boundary layer; climate change; ice-atmosphere interaction; polar climate; water isotopes