In this study, we investigate the mechanism of the arctic warming pattern in surface air temperature (SAT) and sea ice concentrations over the last two decades in comparison with global warming since the 1970s. According to the analysis result, it is found that the patterns of SAT and sea ice before 1989 are mostly determined by the Arctic Oscillation (AO) in winter. In contrast, arctic warming patterns after 1989 are characterized by the intensification of the Beaufort High and the reduced sea-ice concentrations in summer induced by the positive ice-albedo feedback. It is concluded that the arctic warming before 1989 especially in winter was explained by the positive trend of the AOI. Moreover the intensified Beaufort High and the drastic decrease of the sea ice concentrations in September after 1989 were associated with the recent negative trend of the AOI. Since the decadal variation of the AO is recognized as the natural variability of the global atmosphere, it is shown that both of decadal variabilities before and after 1989 in the Arctic can be mostly explained by the natural variability of the AO not by the external response due to the human activity. 1.

Abstract—The benefits of augmenting AMSR-E image data with QuikSCAT image data for supervised sea ice classification in the Western Arctic region are investigated. Experiments compared the performance of a maximum likelihood classifier when used with the AMSR-E only data set against using the combined data. The preferred number of bands to use for classification was examined, as well as whether principal components analysis can be used to reduce the dimensionality of the data. The reliability of training data over time was also investigated. Adding QuikSCAT often improves classifier accuracy in a statistically significant manner and never decreased it significantly when a sufficient number of bands are used. Combining these data sets is beneficial for sea ice mapping. Using all available bands is recommended, data fusion with principal components analysis does not offer any benefit for these data and training data from a specific date remains reliable within 30 days. Index Terms—data fusion, classification, scatterometer, passive microwave, Beaufort Sea, ice mapping, multisensor, principal

accelerate the melt rate, p6 ©evirgen & NASA- iStockphoto ® , p8 ©Domen Colja- Photospin ® , p12 ©Darren Green- Photospin ®, p14 ©kavram- Photospin ® , p16 ©Brian Press Tornado- Photospin ® , p17 ©kavram- Photospin ® , p18 ©Luoman Amazon rainforest deforestation- iStockphoto ® , p22 ©Charles Westerlage Ice carving from Hubbard Glacier- Photospin ® , p28 ©Stephen Schneider Sunset giant iceberg at Ilulissat, p31 ©Jan Martin Will- iStockphoto ® , p32 ©Phil Dickson Ice stack collapsing off the Perito Moreno Glacier, Patagonia Argentina- iStockphoto ®, p34 ©Photospin ® South Pacific Islands, p39 ©Sebastian D’Souza Indian commuters walk through floodwater- Getty Images ® , p42 ©kavram Death Valley- Photospin ® , p45 ©Maxim Tupikov Arctic icebreaker- iStockphoto ® , p46 ©Alexander Hafeman (Mlenny) Dead Vlei Namibia-iStockphoto ® , ©p47 ©E. Steig, p48 ©Ian Joughin Meltwater on the Greenland Ice Sheet, p51 ©Gary Bydlo- Photospin ®,

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Stratigraphy, vol. 6, no. 4, 2009 ABSTRACT: The most recent geologic interval characterized by warm temperatures similar to those projected for the end of this century occurred about 3.3 to 3.0 Ma, during the mid-Piacenzian Age of the Pliocene Epoch. Climate reconstructions of this warm period are integral to both understanding past warm climate equilibria and to predicting responses to today’s transient climate. The Arctic Ocean is of particular interest because in this region climate proxies are rare, and climate models struggle to predict climate sensitivity and the response of sea ice. In order to provide the first quantitative climate data from this region during this interval, sea surface temperatures (SST) were estimated from Ocean Drilling Program Sites 907 and 909 in the Nordic Seas and from Site 911 in the Arctic Ocean based on Mg/Ca of Neogloboquadrina pachyderma (sin) and alkenone unsaturation indices. Evidence of much warmer than modern conditions in the Arctic Ocean during the mid-Piacenzian with temperatures as high as 18°C is presented. In addition, SST anomalies (mid-Piacenzian minus modern) increase with latitude across the North Atlantic and into the Arctic, extending and confirming a reduced mid-Piacenzian pole-to-equator temperature gradient. The agreement between proxies and with previously documented qualitative assessments of intense warming in this region corroborate a poleward transport of heat and an at least seasonally ice-free Arctic, conditions that may serve as a possible analog to future climate if the current rate of Arctic sea-ice reduction continues.

Towards a comprehensive climate change agreement in Copenhagen- Extensive background information and analysis

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ˆ The North Pacific atmosphere-ocean system reflected a combination of a response to La Niña and intrisic variability. The combination of the neutral to weak El Niño expected this winter and a continuation of reduced ice cover in the central Arctic should yield a lighter ice year for the Bering in 2013. ˆ Ocean temperatures remained cold and sea ice remained extensive, similar to 2008 and 2010. Ice retreat this year (and 2009) was the latest recorded since 1985. Summer was calm and cool, but had the most extensive cold pool area of the recent decade. ˆ The summer Calanus copepod time series showed an increase in abundance in 2011 relative to 2010, but remained below the 2009 peak. 2011 was the fourth year that concentrations remained well above average, following patterns also seen in fall zooplankton abundance during cold years. This suggests that prey availability for planktivorous fish, seabirds, and mammals continued to be high during the summer of 2011. ˆ Jellyfish remain abundant, although peak abundances observed in fall 2010 and summer 2011 declined by fall 2011 and summer 2012.