title: Greenland ice sheet melt from MODIS and associated atmospheric variability.
abstract: Daily June-July melt fraction variations over the Greenland ice sheet (GIS) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) (2000-2013) are associated with atmospheric blocking forming an omega-shape ridge over the GIS at 500 hPa height. Blocking activity with a range of time scales, from synoptic waves breaking poleward (<5 days) to full-fledged blocks (≥5 days), brings warm subtropical air masses over the GIS controlling daily surface temperatures and melt. The temperature anomaly of these subtropical air mass intrusions is also important for melting. Based on the years with the greatest melt (2002 and 2012) during the MODIS era, the area-average temperature anomaly of 2 standard deviations above the 14 year June-July mean results in a melt fraction of 40% or more. Though the summer of 2007 had the most blocking days, atmospheric temperature anomalies were too small to instigate extreme melting.
  
  
  CONCLUSIONS
  Short-term atmospheric blocking over Greenland contributes to melt episodesAssociated temperature anomalies are equally important for the meltDuration and strength of blocking events contribute to surface melt intensity.
authors.affiliation: NASA Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: Sirpa
authors.initials: S
authors.lastname: Häkkinen
authors.affiliation: NASA Goddard Space Flight Center Greenbelt, Maryland, USA.
authors.forename: Dorothy K
authors.initials: DK
authors.lastname: Hall
authors.affiliation: NASA Goddard Space Flight Center Greenbelt, Maryland, USA ; Joint Center for Earth Systems Technology (JCET), University of Maryland, Baltimore County Baltimore, Maryland, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Shuman
authors.affiliation: NASA Goddard Space Flight Center Greenbelt, Maryland, USA ; Wyle Information Systems, LLC Lanham, Maryland, USA.
authors.forename: Denise L
authors.initials: DL
authors.lastname: Worthen
authors.affiliation: NASA Goddard Space Flight Center Greenbelt, Maryland, USA ; Science Systems and Applications Inc. Lanham, Maryland, USA.
authors.forename: Nicolo E
authors.initials: NE
authors.lastname: DiGirolamo
keywords: Greenland ice sheet; blocking; melt