Wednesday, 1 May 2013: 11:00 AM
South Room (Renaissance Seattle Hotel)
Arctic Amplification is largely driven by summer sea ice losses. Several studies have identified large scale Northern Hemisphere tropospheric circulation changes during recent fall and winter seasons stemming from the observed decline in ice cover and these alterations in atmospheric flow are increasingly affiliated with changing surface weather conditions in both the high and middle latitudes. Mean monthly and seasonal fields of temperature and pressure compared with respective climatologies provide evidence of this phenomenon. However, analyses of individual weather patterns in conjunction with these surface changes are largely unexplored. Here we employ multiple synoptic climatological approaches to explore relationships between large scale atmospheric circulation and surface weather throughout much of North America from 1979-2011. The Spatial Synoptic Classification (SSC), derived from a set of meteorological variables measured at first order airport weather stations, is used to assess air mass changes at the surface while a circulation pattern classification from NCEP/NCAR Reanalysis is used to examine the atmospheric flow progression in the months following the sea ice minima in September. SSC trends provide evidence that the Arctic Amplification signal may not be confined to the high latitudes, but rather extends to at least 45N. Positive trends in moist polar (MP) air masses at the expense of dry polar air masses are apparent in the fall and winter months, especially at stations near the Arctic Ocean and throughout eastern North America. In November, for example, roughly a 2% per year linear increase in MP classified days is observed at Barrow, while several stations in eastern Canada from Clyde River to Kuujjuarapik display an increase of nearly 0.50% per year in MP days. Diagnosis of prevalent individual weather patterns allows the SSC trends to be put into perspective and provides a synoptic catalogue of flow regimes which can be monitored in the midst of continuing climatic changes in the Arctic.
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