Search

To clarify the contributions of light absorbing snow impurities and glacial microbes to recent abrupt melting of snow/ice in Greenland as part of “Snow impurity and Glacial Microbe effects on the abrupt warming in the Arctic (SIGMA)” Project, two automatic weather stations (AWS) were installed at the sites SIGMA-A (78°03’N, 67°38’W, 1,490 m a.s.l.) on Greenalnd Ice Sheet (GrIS) and SIGMA-B (77°31’N, 69°04’W, 944 m a.s.l.) on Qaanaaq Ice Cap in northwestern Greenland in July 2012. After that the meteorological elements have been measured successfully during one year. Figure 1 depicts the results of air temperatures and snow surface level which indicate that the 2013 summer at SIGMA-A was much colder than 2012 and annual mass balance was positive at the both sites. At SIGMA-A the monthly mean air temperatures in July 2012 and 2013 were 0.2°C and -4.1°C, respectively, and annual mass balance was +102 cm (snow pit result 110 cm). Although the snow surface level decreased by several centimeters in 2012 summer period at SIGMA-A, snow accumulated continueouly in 2013 summer. At SIGMA-B the surface conditions in the 2011 and 2012 summers were bare ice at which glacial microbes covered. However, the snow cover has survived over the 2013 summer at SIGMA-B together with the wide areas higher than 700 m on Qaanaaq Ice Cap. Annual mass balance at SIGMA-B was +68 cm. These contrasting result of meteorological elements between 2012 and 2013 is related with the large-scale circulation patterns around Greenland and the Arctic Ocean. In 2012 the surface melting of GrIS was considerably higher than normal along the western GrIS coast as a result of the enhanced warm southerly air advection associated with the abnormal persistence of anticyclonic circulation centered in South Greenland (Tedesco et al., 2013). However, anticyclonic circulation was centered in the Arctic Ocean, northwest of Greenland in 2013 summer. Furthermore, high albedo due to frequent snowfalls on Qaanaaq Ice Cap in 2013 summer would suppress the surface melting at SIGMA-B., 第4回極域科学シンポジウム個別セッション：[OM] 気水圏11月15日（金） 統計数理研究所 ３階セミナー室１（D305）

第4回極域科学シンポジウム横断セッション：[IC] 極域アイスコア・地形地質・モデリングから迫る古環境変動とそのメカニズム11月12日（火） 統計数理研究所 ３階セミナー室１（D305）

Large-scale climate patterns influenced temperature and weather patterns around the globe in 2011. In particular, a moderate-to-strong La Niña at the beginning of the year dissipated during boreal spring but reemerged during fall. The phenomenon contributed to historical droughts in East Africa, the southern United States, and northern Mexico, as well the wettest two-year period (2010-11) on record for Australia, particularly remarkable as this follows a decade-long dry period. Precipitation patterns in South America were also influenced by La Niña. Heavy rain in Rio de Janeiro in January triggered the country's worst floods and landslides in Brazil's history. The 2011 combined average temperature across global land and ocean surfaces was the coolest since 2008, but was also among the 15 warmest years on record and above the 1981-2010 average. The global sea surface temperature cooled by 0.1°C from 2010 to 2011, associated with cooling influences of La Niña. Global integrals of upper ocean heat content for 2011 were higher than for all prior years, demonstrating the Earth's dominant role of the oceans in the Earth's energy budget. In the upper atmosphere, tropical stratospheric temperatures were anomalously warm, while polar temperatures were anomalously cold. This led to large springtime stratospheric ozone reductions in polar latitudes in both hemispheres. Ozone concentrations in the Arctic stratosphere during March were the lowest for that period since satellite records began in 1979. An extensive, deep, and persistent ozone hole over the Antarctic in September indicates that the recovery to pre-1980 conditions is proceeding very slowly. Atmospheric carbon dioxide concentrations increased by 2.10 ppm in 2011, and exceeded 390 ppm for the first time since instrumental records began. Other greenhouse gases also continued to rise in concentration and the combined effect now represents a 30% increase in radiative forcing over a 1990 baseline. Most ozone depleting substances continued to fall. The global net ocean carbon dioxide uptake for the 2010 transition period from El Niño to La Niña, the most recent period for which analyzed data are available, was estimated to be 1.30 Pg C yr-1, almost 12% below the 29-year long-term average. Relative to the long-term trend, global sea level dropped noticeably in mid-2010 and reached a local minimum in 2011. The drop has been linked to the La Nina conditions that prevailed throughout much of 2010-11. Global sea level increased sharply during the second half of 2011. Global tropical cyclone activity during 2011 was wellbelow average, with a total of 74 storms compared with the 1981-2010 average of 89. Similar to 2010, the North Atlantic was the only basin that experienced abovenormal activity. For the first year since the widespread introduction of the Dvorak intensity-estimation method in the 1980s, only three tropical cyclones reached Category 5 intensity level-all in the Northwest Pacific basin. The Arctic continued to warm at about twice the rate compared with lower latitudes. Below-normal summer snowfall, a decreasing trend in surface albedo, and aboveaverage surface and upper air temperatures resulted in a continued pattern of extreme surface melting, and net snow and ice loss on the Greenland ice sheet. Warmerthan- normal temperatures over the Eurasian Arctic in spring resulted in a new record-low June snow cover extent and spring snow cover duration in this region. In the Canadian Arctic, the mass loss from glaciers and ice caps was the greatest since GRACE measurements began in 2002, continuing a negative trend that began in 1987. New record high temperatures occurred at 20 m below the land surface at all permafrost observatories on the North Slope of Alaska, where measurements began in the late 1970s. Arctic sea ice extent in September 2011 was the second-lowest on record, while the extent of old ice (four and five years) reached a new record minimum that was just 19% of normal. On the opposite pole, austral winter and spring temperatures were more than 3°C above normal over much of the Antarctic continent. However, winter temperatures were below normal in the northern Antarctic Peninsula, which continued the downward trend there during the last 15 years. In summer, an all-time record high temperature of -12.3°C was set at the South Pole station on 25 December, exceeding the previous record by more than a full degree. Antarctic sea ice extent anomalies increased steadily through much of the year, from briefly setting a record low in April, to well above average in December. The latter trend reflects the dispersive effects of low pressure on sea ice and the generally cool conditions around the Antarctic perimeter. © 2012 American Meteorological Society.