doi:10.1007/s00376-017-7026-1

Ballinger T. J., S. C. Sheridan, 2014: Associations between circulation pattern frequencies and sea ice minima in the western Arctic.International Journal of Climatology,34,1385-1394, https://doi.org/10.1002/joc.3767.

10.1002/joc.3767

6b2755da65073129b916b1bc05e2d6b2

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjoc.3767%2Ffull

http://doi.wiley.com/10.1002/joc.2014.34.issue-5ABSTRACTIn this study, a synoptic climatological approach is employed to assess the relationship between the frequency of circulation patterns (CPs) and the latitude of mid-September sea ice minima in the western Arctic. Fifteen CPs are created via principal component analysis and cluster analysis from daily NCEP/NCAR reanalysis sea-level pressure (SLP) fields across a grid from 50 to 90°N and 150°E–100°W from 1979 to 2011. The frequency of these CPs are statistically compared with the latitude of the sea ice minimum from passive microwave data for each of 11 equally-spaced longitudes (176°W to 126°W) extending into the Chukchi and Beaufort Seas. Monthly frequencies for each of the 15 CPs from March to September, signifying the melt season, for each year are correlated with the ice minimum for that September. These monthly frequencies are then entered into a stepwise multiple linear regression (SMLR) and collectively, CP frequencies explain 40–79% of the total ice retreat variance across the longitudes. The frequency of one cluster, CP 11, representing a broad high pressure area over the Beaufort Sea, is highly correlated with the latitude of the sea ice minima; June and August frequencies of this pattern are the initial predictors at 8 of the 11 longitudes and explain 22–32% of the variance. This pattern has occurred more frequently from 2007 onwards; compared with a June mean occurrence of 965days during 1979–2006, CP 11 occurred 16 times in June 2007, and on average more than 1765days per month during June 2008–2011. The Arctic Dipole (AD), Arctic Oscillation (AO), and Pacific-North American (PNA) pattern indices are significantly correlated with CPs 11–13 frequencies throughout certain summer months, further indicating strong relationships between summer circulation and sea ice minima in the region.

Ballinger T. J., J. C. Rogers, 2014: Climatic and atmospheric teleconnection indices and western Arctic sea ice variability.Physical Geography,35,459-477, 2014. 949338.https://doi.org/10.1080/02723646.

10.1080/02723646.2014.949338

f22a4c450fb64d768d6b505ea2c42bf3

http%3A%2F%2Fwww.tandfonline.com%2Fdoi%2Fref%2F10.1080%2F02723646.2014.949338

http://www.tandfonline.com/doi/abs/10.1080/02723646.2014.949338This study examines the sea ice cover minima in the western Arctic in the context of several climatic mechanisms known to impact its variability. The September latitude of western Arctic sea ice is measured along 11 equally-spaced longitudes extending from 1760265W to 1260265W in the Chukchi and Beaufort Seas, 1953–2010. Indices of seasonal atmospheric and oceanic teleconnections and annual mean Northern Hemisphere temperatures (NHT) and CO2 concentration are orthogonalized using rotated principal component analysis, forming predictors regressed onto the sea ice latitude data at each longitude using stepwise multiple linear regression. Prior to 1998, small amounts of September ice edge variance are explained by teleconnections such as the Arctic Dipole, Arctic Oscillation, and Pacific-North American Pattern. NHTs begin explaining large amounts of ice edge variance starting in 1998. For the 1953–2010 period, up to 68% of the ice edge variance is explained at 161°65W in the Chukchi Sea, mostly by NHTs. With the exception of the three easternmost longitudes (136–126°65W), the teleconnections and NHTs explain over 50% of the regional ice edge variance. Increases in both NHTs and ice retreat since the mid-1990s account for the large explained variances observed in regression analyses extending into recent years.

Ballinger T. J., S. C. Sheridan, and E. Hanna, 2014: Resolving the Beaufort Sea High using synoptic climatological methods.International Journal of Climatology,34,3312-3319, https://doi.org/10.1002/joc.3907.

10.1002/joc.3907

4cae6fe6975f7a00d99309e358fad4f3

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjoc.3907%2Fpdf

http://doi.wiley.com/10.1002/joc.3907ABSTRACT Melt season frequencies of the Beaufort Sea High (BSH) have a profound effect on western Arctic climate, making the interannual spatial and temporal monitoring of this polar anticyclone important. This manuscript presents two automated synoptic climatological analyses using a two-step cluster procedure to classify daily mean sea level pressure (MSLP) over 180–120°W and 70–85°N with an emphasis on identifying BSH patterns. Separate raw and anomaly MSLP circulation pattern (CP) classifications are compared in order to assess the spatial characteristics of the BSH and its monthly frequency changes during the melt season from 1979 to 2012. Analysis of both classifications shows clear advantages to using the anomaly approach in terms of assessing temporal and spatial changes, particularly in light of the documented recent atmospheric circulation changes that have been observed over the region. Associations between the June anomaly circulation pattern (ACP) 5, a +465hPa BSH pattern situated between 155°W and 135°W, and June indices of atmospheric teleconnections such as the Arctic Dipole and Arctic Oscillation are statistically significant. There is also a statistically significant link to the downstream Greenland Blocking Index; suggesting that the BSH may be intricately related to climatic variability outside the analysed domain as well. Further, ACP 5 occurred nearly 365weeks more often during the melt season in recent massive Arctic Sea ice loss years (2007–2012) compared with the climatology (1979–2006). Recent increases in June ACP 5 frequencies account for a large proportion of this pattern's long-term frequency changes.

Baxter S., S. Nigam, 2015: Key role of the North Pacific Oscillation-West Pacific Pattern in generating the extreme 2013/14 North American winter.J. Climate,28,8109-8117, https://doi.org/10.1175/JCLI-D-14-00726.1.

10.1175/JCLI-D-14-00726.1

be042c36ff118a305a02bc7a06169f5c

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F283028588_Key_Role_of_North_Pacific_OscillationWest_Pacific_Pattern_in_Generating_the_Extreme_2013-2014_North_American_Winter

http://journals.ametsoc.org/doi/10.1175/JCLI-D-14-00726.1Not Available

Belleflamme A., X. Fettweis, and M. Erpicum, 2015: Recent summer Arctic atmospheric circulation anomalies in a historical perspective.The Cryosphere,9,53-64, .http://doi.org/10.5194/tc-9-53-2015

10.5194/tc-9-53-2015

fc4a54bbdf2e5d6dc3e18ecb71130640

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2014TCD.....8.4823B

http://www.the-cryosphere.net/9/53/2015/A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500 hPa geopotential height data from five reanalysis data sets (ERA-Interim, ERA-40, NCEP/NCAR, ERA-20C, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 20072012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. For example, only ERA-20C shows circulation anomalies that could explain the 19201930 summertime Greenland warming, in contrast to 20CRv2. While the recent anomalies exceed by a factor of 2 the interannual variability of the atmospheric circulation of the Arctic region, their origin (natural variability or global warming) remains debatable.

Bezeau P., M. Sharp, and G. Gascon, 2015: Variability in summer anticyclonic circulation over the Canadian Arctic Archipelago and west Greenland in the late 20th/early 21st centuries and its effect on glacier mass balance.International Journal of Climatology,35,540-557, https://doi.org/10.1002/joc.4000.

10.1002/joc.4000

20fe468a4d70ab541bf7d64959a5e511

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjoc.4000%2Fpdf

http://doi.wiley.com/10.1002/joc.2015.35.issue-4ABSTRACT More frequent summer anticyclonic circulation over the Canadian Arctic Archipelago (CAA) between 2007 and 2012 caused more intense and sustained melt of ice caps and glaciers and increased rates of mass loss. To determine the frequency of the occurrence of anticyclonic circulation over the CAA and western Greenland, a self-organizing map (SOM) was used to classify daily 500 hPa geopotential height (GPH) anomalies calculated from National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) Reanalysis 1 (1948–2012) and five Coupled Model Intercomparison Project Phase 5 (CMIP5) models (1950–2025). While the NCEP/NCAR reanalysis indicates that significant summer warming over the CAA is linked to a doubling in the frequency of anticyclonic circulation over the region since 2007, the CMIP5 models were not capable of reproducing the magnitude of the trend in the frequency of anticyclonic circulation over the CAA and western Greenland found in NCEP/NCAR. The variability of the frequency of positive anomalies in summer 500 hPa GPH was found to be related to variability of Arctic sea ice volume/thickness in April, May and June (1979–2012) and to poleward eddy heat flux in June (1979–2012).

Bond N. A., D. E. Harrison, 2006: ENSO's effect on Alaska during opposite phases of the Arctic Oscillation.International Journal of Climatology,26,1821-1841, https://doi.org/10.1002/joc.1339.

10.1002/joc.1339

0f43d29492b8fe5ed50ad52745de1ca8

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjoc.1339%2Ffull

http://doi.wiley.com/10.1002/%28ISSN%291097-0088The NCEP Reanalysis and station data are used to investigate how the winter weather of Alaska during El Ni09o/Southern Oscillation (ENSO) events has varied during different phases of the Arctic Oscillation (AO). Much greater 500-hPa geopotential height, 1000-hPa air temperature, and precipitation anomalies in association with ENSO tend to occur in the negative phase of the AO; these anomalies cannot be attributed to the AO on its own. Analysis of case-to-case variability indicates that the ENSO/AO composite results are robust. It is also shown that much of the variability of the Pacific pole of the AO is associated with those winters with El Ni09o/AO- and La Ni09a/AO+ conditions, suggesting that this pole is much less robust than its counterpart in the North Atlantic. To the extent that winter mean state of the AO can be predicted, our results indicate that incorporation of the state of the AO would provide useful information for improving seasonal weather forecasts in the vicinity of Alaska. Copyright 08 2006 Royal Meteorological Society

Bond N. A., M. F. Cronin, H. Freeland , and N. Mantua, 2015: Causes and impacts of the 2014 warm anomaly in the NE Pacific.Geophys. Res. Lett.,42,3414-3420, https://doi.org/10.1002/2015GL063306.

10.1002/2015GL063306

bf674f38b49248ba8d62874c4fe6b0f4

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2015GeoRL..42.3414B

http://doi.wiley.com/10.1002/2015GL063306Abstract Strongly positive temperature anomalies developed in the NE Pacific Ocean during the boreal winter of 20132014. Based on a mixed layer temperature budget, these anomalies were caused by lower than normal rates of the loss of heat from the ocean to the atmosphere and of relatively weak cold advection in the upper ocean. Both of these mechanisms can be attributed to an unusually strong and persistent weather pattern featuring much higher than normal sea level pressure over the waters of interest. This anomaly was the greatest observed in this region since at least the 1980s. The region of warm sea surface temperature anomalies subsequently expanded and reached coastal waters in spring and summer 2014. Impacts on fisheries and regional weather are discussed. It is found that sea surface temperature anomalies in this region affect air temperatures downwind in Washington state.

Cassano E. N., J. M. Glisan, J. J. Cassano, W. J. Gutowski Jr., and M. W. Seefeldt, 2015: Self-organizing map analysis of widespread temperature extremes in Alaska and Canada.Climate Research,62,199-218, https://doi.org/10.3354/cr01274.

10.3354/cr01274

470c5408ade1dcd022121e14bcced0d6

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F272391831_self-organizing_map_analysis_of_widespread_temperature_extremes_in_alaska_and_canada

http://www.int-res.com/abstracts/cr/v62/n3/p199-218/Abstract This paper demonstrates how self-organizing maps (SOMs) can be used to evaluate the large-scale environment, in particular the synoptic circulation associated with widespread temperature extremes. The paper provides details on how SOMs are created, how they can be used to understand extreme events, and lessons learned in applying this methodology for extremes analysis. Using a SOM can be helpful in understanding the underlying physical processes that control extreme events, and how the extremes and the processes that control them may change in time or differ across space. Examples of widespread daily temperature extremes in 4 regions: 2 each in Alaska and in northern Canada during winter (December, January, and February) for 1989-2007 are presented to illustrate the application of the methodology. For the regions studied, the size of the domain over which the synoptic circulation was defined-in particular using a smaller domain focused on particular regions-and a greater number of classes to represent the archetypical synoptic patterns for the regions, give the best relationship between synoptic circulation and extremes. The results are most robust for the Alaskan domains and less so for the Canadian domains, leading to the conclusion that further study is warranted to better understand extremes in the Canadian regions.

Holland, M. M., C. M. Bitz, 2003: Polar amplification of climate change in coupled models.Climate Dyn.,21,221-232, https://doi.org/10.1007/s00382-003-0332-6.

10.1007/s00382-003-0332-6

db8a6c564214d769082f8bc86e537f15

http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fkpb6v1cg4ubab4aj

http://link.springer.com/10.1007/s00382-003-0332-6The Northern Hemisphere polar amplification of climate change is documented in models taking part in the Coupled Model Intercomparison Project and in the new version of the Community Climate System Mo

IPCC, 2013: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker,T.F.,D. Qin,G.-K. Plattner,M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1535 pp.

Liu J. P., J. A. Curry, and Y. Y. Hu, 2004: Recent Arctic sea ice variability: Connections to the Arctic Oscillation and the ENSO,Geophys. Res. Lett.,31,L09211, https://doi.org/10.1029/2004GL019858.

10.1029/2004GL019858

923982f755a3c0f42059a2090b6a0361

http%3A%2F%2Fwww.europepmc.org%2Fabstract%2FMED%2F15798817

http://www.europepmc.org/abstract/MED/15798817Trends in the satellite-derived Arctic sea ice concentrations (1978-2002) show pronounced decreases in the Barents/Kara Seas, between the Chukchi and Beaufort Seas, the central Sea of Okhotsk and a portion of the Hudson/Baffin Bay by ~2-8% per decade, exceeding the 95% confidence level. Qualitatively speaking, positive phases of the Arctic Oscillation (AO) and El Niño-Southern Oscillation (ENSO) produce similar ice changes in the western Arctic, but opposite ice changes in the eastern Arctic. The manner in which the ice changes are related to the AO and ENSO are demonstrated. Over the last 24 years, the magnitude of the ice changes associated with the positive AO trend and the negative ENSO trend is much smaller than the regional ice trends. Thus, more local or less understood large scale processes should be investigated for explanations.

Makshtas A. P., I. I. Bolshakova, R. M. Gun, O. L. Jukova, N. E. Ivanov, and S. V. Shutilin, 2011: Climate of the hydrometeorological observatory Tiksi region. Meteorological and Geophysical Investigations, M, Paulsen, Ed., 49- 74.

Newman, M., Coauthors, 2016: The Pacific decadal oscillation,revisited. J. Climate,29,4399-4427,.https://doi.org/10.1175/JCLI-D-15-0508.1

10.1175/JCLI-D-15-0508.1

c5b0517c32f0b5af99a1969e58d33516

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2016AGUFMPC23A..07M

http://journals.ametsoc.org/doi/10.1175/JCLI-D-15-0508.1Since its identification in the late 1990's as the dominant pattern of North Pacific sea surface temperature (SST) variability, the Pacific decadal oscillation (PDO) has been connected both to other parts of the climate system and to impacts on natural resources and marine and terrestrial ecosystems. Variability associated with the PDO has often been confused with externally forced climate change including anthropogenic effects. Subsequent research, however, has found that the PDO is not a single physical mode of climate variability but instead largely represents the combination of three groups of processes: (1) changes in ocean surface heat fluxes and Ekman (wind-driven) transport related to the Aleutian low, due to both local, rapidly decorrelating, unpredictable weather noise and to remote forcing from interannual to decadal tropical variability (largely El Nino) via the "atmospheric bridge"; (2) ocean memory, or processes determining oceanic thermal inertia including "re-emergence" and oceanic Rossby waves, that act to integrate this forcing and thus generate added PDO variability on decadal time scales; and (3) decadal changes in the Kuroshio-Oyashio current system forced by the multi-year history of basin-wide Ekman pumping, manifested as SST anomalies along the subarctic front at about 40N in the western Pacific ocean. Thus, the PDO represents the effects of different processes operating on different timescales, with few of its apparent impacts due to extratropical SST anomalies. This talk presents a synthesis of this current view of the PDO, and discusses corresponding implications for climate diagnosis, including of PDO climate impacts and predictability (both oceanographic and atmospheric); potential decadal regime-like behavior; simulations of the PDO in climate models; the interpretation of paleoclimate multicentennial reconstructions of the PDO; and its impacts on marine ecosystems. We conclude with some suggested "best practices" for future PDO diagnosis and forecasts including investigating the potential role of the PDO in the global temperature hiatus.

Overland, J. E., M. Y. Wang, 2005: The third Arctic climate pattern: 1930s and early 2000s,Geophys. Res. Lett.,32,L23808, https://doi.org/10.1029/2005GL024254.

10.1029/2005GL024254

e1566c2ac241cc167f3a76d7d43baa28

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2005GL024254%2Fpdf

http://doi.wiley.com/10.1029/2005GL024254Persistent near-surface warm temperature anomalies have occurred in two localized areas, eastern Siberia/East Siberian Sea and northeastern Canada/Baffin Bay, during winter and spring in recent years (2000-2005) in contrast to previous decades. The proximate cause in winter was a northward displacement and strengthening of the Aleutian Low and a weakening of the Icelandic Low. Spring showed a dipole pattern with higher sea-level pressure (SLP) on the North American side of the Arctic and lower pressures over Eurasia. Phase space trajectories of arctic climate for 1951-2005 based on the first two EOFs of SLP, the Arctic Oscillation and a Pacific North American-like (PNA*) pattern, show multi-annual variability leading to lower SLP and warmer temperatures in the last decades of the 20th century. Recent winters have some projection onto PNA*, but the SLP dipole in recent springs does not strongly project onto either of the two basic climate patterns. The period from 1928-1935 also had a dipole structure in SLP, which contributed to the interdecadal arctic-wide warm temperature anomalies in the first half of the 20th century. Recognition of the recent persistent and somewhat unique Arctic climate pattern is important as it contributes to the ongoing reorganization of arctic ecosystems.

Overland, J. E., D. B. Percival, H. O. Mofjeld, 2006: Regime shifts and red noise in the North Pacific.Deep Sea Research Part I,53,582-588, 2005. 12. 011.https://doi.org/10.1016/j.dsr.

10.1016/j.dsr.2005.12.011

a4eb67d8f4faa3a36dccdbdd0a88699f

http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0967063706000136

http://linkinghub.elsevier.com/retrieve/pii/S0967063706000136Regimes and regime shifts are important concepts for understanding decadal variability in the physical system of the North Pacific because of the potential for an ecosystem to reorganize itself in response to such shifts. There are two prevalent senses in which these concepts are taken in the literature. The first is a formal definition and posits multiple stable states and rapid transitions between these states. The second is more data-oriented and identifies local regimes based on differing average climatic levels over a multi-annual duration, i.e. simply interdecadal fluctuations. This second definition is consistent with realizations from stochastic red noise processes to a degree that depends upon the particular model. Even in 100 year long records for the North Pacific a definition of regimes based solely on distinct multiple stable states is difficult to prove or disprove, while on interdecadal scales there are apparent local step-like features and multi-year intervals where the state remains consistently above or below the long-term mean. The terminologies climatic regime shift, statistical regime shift or climatic event are useful for distinguishing this second definition from the first. To illustrate the difficulty of advocating one definition over the other based upon a relatively short time series, we compare three simple models for the Pacific Decadal Oscillation (PDO). The 104-year PDO record is insufficient to statistically distinguish a single preference between a square wave oscillator consistent with the formal definition for regime shifts, and two red noise models that are compatible with climatic regime shifts. Because of the inability to distinguish between underlying processes based upon data, it is necessary to entertain multiple models and to consider how each model would impact resource management. In particular the persistence in the fitted models implies that certain probabilistic statements can be made regarding climatic regime shifts, but we caution against extrapolation to future states based on curve fitting techniques.

Overland, J. E., J. A. Francis, E. Hanna, M. Y. Wang, 2012: The recent shift in early summer arctic atmospheric circulation,Geophys. Res. Lett.,39,L19804, https://doi.org/10.1029/2012GL053268.

10.1029/2012GL053268

2e8c1ffd3dfb366f67043320fcb1479d

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2012GL053268%2Ffull

http://onlinelibrary.wiley.com/doi/10.1029/2012GL053268/fullThe last six years (2007-2012) show a persistent change in early summer Arctic wind patterns relative to previous decades. The persistent pattern, which has been previously recognized as the Arctic Dipole (AD), is characterized by relatively low sea-level pressure over the Siberian Arctic with high pressure over the Beaufort Sea, extending across northern North America and over Greenland. Pressure differences peak in June. In a search for a proximate cause for the newly persistent AD pattern, we note that the composite 700 hPa geopotential height field during June 2007-2012 exhibits a positive anomaly only on the North American side of the Arctic, thus creating the enhanced mean meridional flow across the Arctic. Coupled impacts of the new persistent pattern are increased sea ice loss in summer, long-lived positive temperature anomalies and ice sheet loss in west Greenland, and a possible increase in Arctic-subarctic weather linkages through higher-amplitude upper-level flow. The North American location of increased 700 hPa positive anomalies suggests that a regional atmospheric blocking mechanism is responsible for the presence of the AD pattern, consistent with observations of unprecedented high pressure anomalies over Greenland since 2007.

Overland, J. E., J. Wang, R. S. Pickart, M. Y. Wang, 2014a: Recent and future changes in the meteorology of the Pacific Arctic.The Pacific Arctic Region,J. Grebmeier and W. Maslowski,Eds., Springer, Dordrecht, 17-30, https://doi.org/10.1007/978-94-017-8863-2_2.

10.1007/978-94-017-8863-2_2

c2290bcdb6f73e490344f7e49e287c6d

http%3A%2F%2Fwww.springerlink.com%2Fopenurl.asp%3Fid%3Ddoi%3A10.1007%2F978-94-017-8863-2_2

http://www.springerlink.com/openurl.asp?id=doi:10.1007/978-94-017-8863-2_2The meteorology of the Pacific Arctic (the Bering Sea through the Chukchi and southern Beaufort Seas) represents the transition zone between the moist and relatively warm maritime air mass of the Paci

Overland, J. E., M. Y. Wang, J. E. Walsh, J. C. Stroeve, 2014b: Future Arctic climate changes: Adaptation and mitigation time scales.Earth's Future,2,68-74, https://doi.org/10.1002/2013EF000162.

10.1002/2013EF000162

7f3fcffe2efe5dba0951b34954bac95c

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2F2013EF000162%2Fabstract

http://doi.wiley.com/10.1002/eft2.2014.2.issue-2The climate in the Arctic is changing faster than in midlatitudes. This is shown by increased temperatures, loss of summer sea ice, earlier snow melt, impacts on ecosystems, and increased economic access. Arctic sea ice volume has decreased by 75% since the 1980s. Long-lasting global anthropogenic forcing from carbon dioxide has increased over the previous decades and is anticipated to increase over the next decades. Temperature increases in response to greenhouse gases are amplified in the Arctic through feedback processes associated with shifts in albedo, ocean and land heat storage, and near-surface longwave radiation fluxes. Thus, for the next few decades out to 2040, continuing environmental changes in the Arctic are very likely, and the appropriate response is to plan for adaptation to these changes. For example, it is very likely that the Arctic Ocean will become seasonally nearly sea ice free before 2050 and possibly within a decade or two, which in turn will further increase Arctic temperatures, economic access, and ecological shifts. Mitigation becomes an important option to reduce potential Arctic impacts in the second half of the 21st century. Using the most recent set of climate model projections (CMIP5), multimodel mean temperature projections show an Arctic-wide end of century increase of +13ºC in late fall and +5ºC in late spring for a business-as-usual emission scenario (RCP8.5) in contrast to +7ºC in late fall and +3ºC in late spring if civilization follows a mitigation scenario (RCP4.5). Such temperature increases demonstrate the heightened sensitivity of the Arctic to greenhouse gas forcing.

Papineau J. M., 2001: Wintertime temperature anomalies in Alaska correlated with ENSO and PDO.International Journal of Climatology,21,1577-1592, 686.https://doi.org/10.1002/joc.

10.1002/joc.686

610b488ff7d125c850010cf8d8eee62e

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fjoc.686%2Ffull

http://doi.wiley.com/10.1002/%28ISSN%291097-0088Wintertime (November-March) surface air temperatures at 14 stations throughout the state of Alaska are correlated with the Southern Oscillation Index and the Pacific Decadal Oscillation index, for the years 1954-2000. On the seasonal and monthly timescales, the principal results are: (i) During El Niño winters, temperatures are near normal in western Alaska but significantly warmer than normal for the eastern two-thirds of the state. (ii) La Niña winters produce significant below normal temperatures statewide. (iii) Temperature patterns produced during El Niño, La Niña, and neutral winters are modified by the concurrent state of the North Pacific sea-surface temperature anomalies, as indicated by the Pacific Decadal Oscillation index.On the sub-monthly timescale, temperatures across Alaska are to the first order correlated with the alternating zonal to meridional Pacific/North American pattern. Analysis of daily winter temperatures at Fairbanks indicates that cold anomalies are more frequent and are longer in duration than warm anomalies, primarily due to radiational cooling of the boundary layer and the subsequent formation of deep temperature inversions. The development of strong inversions over the interior of Alaska limits the response of temperatures to changes in the synoptic-scale flow pattern. Warm anomalies in contrast to cold anomalies, are primarily a function of warm air advection, therefore temperatures during warm anomalies fluctuate in phase with changes in the synoptic-scale flow. Ultimately, air temperatures across Alaska are a function of: synoptic-scale forcings, radiative cooling of the boundary layer as well as local and regional effects such as downslope and drainage winds.

Petrie R. E., L. C. Shaffrey, and R. T. Sutton, 2015: Atmospheric response in summer linked to recent Arctic sea ice loss.Quart. J. Roy. Meteor. Soc.,141,2070-2076, https://doi.org/10.1002/qj.2502.

10.1002/qj.2502

fe35f6b81f788cdf7a263c9bbc8cca1e

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1002%2Fqj.2502%2Fpdf

http://doi.wiley.com/10.1002/qj.2502Since 2007 a large decline in Arctic sea ice has been observed. The large-scale atmospheric circulation response to this decline is investigated in ERA-Interim reanalyses and HadGEM3 climate model experiments. In winter, post-2007 observed circulation anomalies over the Arctic, North Atlantic and Eurasia are small compared to interannual variability. In summer, the post-2007 observed circulation is dominated by an anticyclonic anomaly over Greenland which has a large signal-to-noise ratio. Climate model experiments driven by observed SST and sea ice anomalies are able to capture the summertime pattern of observed circulation anomalies, although the magnitude is a third of that observed. The experiments suggest high SSTs and reduced sea ice in the Labrador Sea lead to positive temperature anomalies in the lower troposphere which weaken the westerlies over North America through thermal wind balance. The experiments also capture cyclonic anomalies over Northwest Europe, which are consistent with downstream Rossby wave propagation.

Pithan F., T. Mauritsen, 2014: Arctic amplification dominated by temperature feedbacks in contemporary climate models.Nature Geoscience,7,181-184, https://doi.org/10.1038/ngeo2071.

10.1038/NGEO2071

4c0d1f247661d1585ddd33bc92734553

http%3A%2F%2Fwww.nature.com%2Fngeo%2Fjournal%2Fvaop%2Fncurrent%2Ffull%2Fngeo2071.html%3Fial%3D1

http://www.nature.com/doifinder/10.1038/ngeo2071Climate change is amplified in the Arctic region. Arctic amplification has been found in past warm and glacial periods, as well as in historical observations and climate model experiments. Feedback effects associated with temperature, water vapour and clouds have been suggested to contribute to amplified warming in the Arctic, but the surface albedo feedback--the increase in surface absorption of solar radiation when snow and ice retreat--is often cited as the main contributor. However, Arctic amplification is also found in models without changes in snow and ice cover. Here we analyse climate model simulations from the Coupled Model Intercomparison Project Phase 5 archive to quantify the contributions of the various feedbacks. We find that in the simulations, the largest contribution to Arctic amplification comes from a temperature feedbacks: as the surface warms, more energy is radiated back to space in low latitudes, compared with the Arctic. This effect can be attributed to both the different vertical structure of the warming in high and low latitudes, and a smaller increase in emitted blackbody radiation per unit warming at colder temperatures. We find that the surface albedo feedback is the second main contributor to Arctic amplification and that other contributions are substantially smaller or even opposeArctic amplification.

Serreze M. C., R. G. Barry, 2011: Processes and impacts of Arctic amplification: A research synthesis.Global and Planetary Change,77,85-96, 2011. 03. 004.https://doi.org/10.1016/j.gloplacha.

10.1016/j.gloplacha.2011.03.004

e13513b501cd20f1448d7b3a5223b0d8

http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0921818111000397

http://linkinghub.elsevier.com/retrieve/pii/S092181811100039778 Temperature changes in the Arctic tend to exceed those for the globe as whole. 78 This phenomenon is termed Arctic amplification. 78 Arctic amplification has many causes operating on different time and space scales. 78 Recent Arctic amplification is strongly linked to declining sea ice extent. 78 Arctic amplification is expected to strengthen in coming decades. 78 Impacts of Arctic amplification will extend well beyond the Arctic region.

Stroeve J. C., M. C. Serreze, M. M. Holland , J. E. Kay, J. Maslanik, and A. P. Barrett, 2012: The Arctic's rapidly shrinking sea ice cover: A research synthesis.Climatic Change,110,1005-1027, https://doi.org/10.1007/s10584-011-0101-1.

10.1007/s10584-011-0101-1

ec8b873b2b60c944d0c2481e739dc69f

http%3A%2F%2Fplankt.oxfordjournals.org%2Fexternal-ref%3Faccess_num%3D10.1007%2Fs10584-011-0101-1%26amp%3Blink_type%3DDOI

http://link.springer.com/10.1007/s10584-011-0101-1

Walsh J., P. A. Bieniek, B. Brettschneider, E. S. Euskirchen, R. Lader, and R. L. Thoman, 2017: The exceptionally warm winter of 2015/16 in Alaska.J. Climate,30,2069-2088, https://doi.org/10.1175/JCLI-D-16-0473.1.

10.1175/JCLI-D-16-0473.1

6894d8111b688fb144ebbeb3890978f7

http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F312240541_The_exceptionally_warm_winter_of_2015-16_in_Alaska

http://journals.ametsoc.org/doi/10.1175/JCLI-D-16-0473.1Abstract Alaska experienced record-setting warmth during the 2015/16 cold season (October-April). Statewide average temperatures exceeded the period-of-record mean by more than 4ºC over the 7-month cold season and by more than 6ºC over the 4-month late-winter period, January-April. The record warmth raises two questions: 1) Why was Alaska so warm during the 2015/16 cold season? 2) At what point in the future might this warmth become typical if greenhouse warming continues? On the basis of circulation analogs computed from sea level pressure and 850-hPa geopotential height fields, the atmospheric circulation explains less than half of the anomalous warmth. The warming signal forced by greenhouse gases in climate models accounts for about 1ºC of the anomalous warmth. A factor that is consistent with the seasonal and spatial patterns of the warmth is the anomalous surface state. The surface anomalies include 1) above-normal ocean surface temperatures and below-normal sea ice coverage in the surrounding seas from which air advects into Alaska and 2) the deficient snowpack over Alaska itself. The location of the maximum of anomalous warmth over Alaska and the late-winter-early-spring increase of the anomalous warmth unexplained by the atmospheric circulation implicates snow cover and its albedo effect, which is supported by observational measurements in the boreal forest and tundra biomes. Climate model simulations indicate that warmth of this magnitude will become the norm by the 2050s if greenhouse gas emissions follow their present scenario.

Wang J., J. L. Zhang, E. Watanabe, M. Ikeda, K. Mizobata, J. E. Walsh, X. Z. Bai, and B. Y. Wu, 2009: Is the Dipole Anomaly a major driver to record lows in Arctic summer sea ice extent? Geophys,Res. Lett.,36,L05706, https://doi.org/10.1029/2008GL036706.

10.1029/2008GL036706

dc317c59aee19cdfbea4f5e415bfc1f3

http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F2008GL036706%2Ffull

http://onlinelibrary.wiley.com/doi/10.1029/2008GL036706/full[1] Recent record lows of Arctic summer sea ice extent are found to be triggered by the Arctic atmospheric Dipole Anomaly (DA) pattern. This local, second-leading mode of sea-level pressure (SLP) anomaly in the Arctic produced a strong meridional wind anomaly that drove more sea ice out of the Arctic Ocean from the western to the eastern Arctic into the northern Atlantic during the summers of 1995, 1999, 2002, 2005, and 2007. In the 2007 summer, the DA also enhanced anomalous oceanic heat flux into the Arctic Ocean via Bering Strait, which accelerated bottom and lateral melting of sea ice and amplified the ice-albedo feedback. A coupled ice-ocean model was used to confirm the historical record lows of summer sea ice extent.

Wang, J., Coauthors, 2014: Abrupt climate changes and emerging ice-ocean processes in the Pacific Arctic region and the Bering Sea.The Pacific Arctic Region,J. Grebmeier and W. Maslowski,Eds., Springer, 65-99, https://doi.org/10.1007/978-94-017-8863-2_4.

Wang M. Y., J. E. Overland, 2015: Projected future duration of the sea-ice-free season in the Alaskan Arctic.Progress in Oceanography,136,50-59, 2015. 01. 001.https://doi.org/10.1016/j.pocean.

10.1016/j.pocean.2015.01.001

65763aa38c621aae8348c52e4b032be4

http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0079661115000038

http://linkinghub.elsevier.com/retrieve/pii/S0079661115000038Global warming and continued reduction in sea ice cover will result in longer open water duration in the Arctic, which is important for the shipping industry, marine mammals, and other components of the regional ecosystem. In this study we assess the length of open water duration in the Alaskan Arctic over the next few decades using the set of latest coupled climate models (CMIP5). The Alaskan Arctic, including the Chukchi and the Beaufort Sea, has been a major region of summer sea ice retreat since 2007. Thirty five climate models from CMIP5 are evaluated and twelve are selected for composite projections based on their historical simulation performance. In the regions north of the Bering Strait (north of 70° N), future open-water duration shifts from a current 3–4months to a projected near 5months by 2040 based on the mean of the twelve selected climate models. There is considerable north–south gradient in projected durations. Open water duration is about 1month shorter along the same latitudes in the Beaufort Sea compared with that in the Chukchi Sea. Uncertainty is generally ±1month estimated from the range of model results. Open-water duration in the Alaskan Arctic expands quickly in these models over the next decades which will impact regional economic access and potentially alter ecosystems. Yet the northern Alaskan Arctic from January through May will remain sea ice covered into the second half of the century due to normal lack of sunlight.

Wang M., Q. Yang, J. E. Overland , and P. Stabeno, 2017: Sea-ice Evolution in the Pacific Arctic: the present to mid-century by selected CMIP5 models. Deep Sea Research Part II, (in press).

Wassmann P., 2015: Overarching perspectives of contemporary and future ecosystems in the Arctic Ocean.Progress in Oceanography,139,1-12, 2015. 08. 004.https://doi.org/10.1016/j.pocean.

10.1016/j.pocean.2015.08.004

502d15444a2cd101e9da1698307bbe11

http%3A%2F%2Fwww.sciencedirect.com%2Fscience%2Farticle%2Fpii%2FS0079661115001767

http://linkinghub.elsevier.com/retrieve/pii/S0079661115001767The Arctic region has a number of specific characteristics that provide the region an exceptional global position. It comprises 5% of the earth surface, 1% of world ocean volume, 3% of world ocean area, 25% of world continental shelf, 35% of world coastline, 11% of global river runoff and 20 of worlds 100 longest rivers. The Arctic region encompasses only 0.05% of the global population, but 22% undiscovered petroleum, 15% of global petroleum production, many metals and non-metals resources and support major global fisheries (60 and 80ºN). In times of increasing resource demand and limitation the world focuses increasingly onto the Arctic Ocean (AO) and adjacent regions. This development is emphasised by the recent awareness of rapid climate change in the AO, the most significant on the globe, and has resulted in increased attention to the oceanography of the high north. The loss of Arctic sea ice has emerged as a leading signal of global warming. It is taking place at a rate 2-3 times faster than global rates and sea-ice cover has decreased more than 10% per decade, while sea-ice volume may have been reduced by minimum 40% over the last 30 years (Meier et al., 2014). The reduction of ice cover and thickness makes the region available for commercial interest. The region drives also critical effects on the biophysical, political and economic system of the Northern Hemisphere (e.g., Grambling, 2015). These striking changes in physical forcing have left marine ecological footprints of climate change in the Arctic ecosystem (Wassmann et al., 2011). However, predicting the future of the pan-Arctic ecosystem remains a challenge not only because of the ever-accelerating nature of both physical and biological alterations, but also because of lack of marine ecological knowledge, that is staggering for the majority of regions (except the Barents, Chukchi and Beaufort seas).

Wood K. R., J. E. Overland , S. A. Salo, N. A. Bond, W. J. Williams, and X. Q. Dong, 2013: Is there a "new normal" climate in the Beaufort Sea? Polar Research,32, 19552, .https://doi.org/10.3402/polar.v32i0.19552

10.3402/polar.v32i0.19552

d561954eba737d72699e336dce00b7eb

http%3A%2F%2Fdx.doi.org%2F10.3402%2Fpolar.v32i0.19552

https://www.tandfonline.com/doi/full/10.3402/polar.v32i0.19552ABSTRACT Since 2007, environmental conditions in the Beaufort Sea have appeared to be consistently different from those in the past. Is a ‘‘new normal’’ climate emerging in the region? Sea-surface temperatures (SSTs) have been notably warm during the summer, leading to delayed freeze-up in the fall along with large surface air temperature (SAT) anomalies due to the release of stored ocean heat to the atmosphere. In the autumn of 2011 and 2012, SST and SAT anomalies in Arctic marginal seas were the largest observed in the Northern Hemisphere. Since 2007, there has been an increase in easterly winds, which has helped set the stage for Arctic amplification by advecting sea ice out of the region and enhancing surface stratification due to the offshore transport of fresh water from the large Mackenzie River discharge plume. These winds are linked to an intensification of the Beaufort High and are evident throughout the troposphere. Their occurrence has undoubtedly contributed to the acceleration of sea-ice loss and surface warming in the Beaufort Sea, with additional impacts likely throughout the ecosystem. Keywords : Arctic change; sea ice; Beaufort Sea; Mackenzie River; Arctic amplification; atmospheric circulation (Published: 17 October 2013) To access the supplementary material for this article, please see Supplementary files in the column to the right (under Article Tools). Citation : Polar Research 2013, 32 , 19552, http://dx.doi.org/10.3402/polar.v32i0.19552

Wu B. Y., J. Wang, and J. E. Walsh, 2006: Dipole anomaly in the winter arctic atmosphere and its association with sea ice motion.J. Climate,19,210-225, .http://doi.org/10.1175/JCLI3619.1

10.1175/JCLI3619.1

2dcd3e6176f828a6903aace74538914e

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2006JCli...19..210W

http://journals.ametsoc.org/doi/abs/10.1175/JCLI3619.1This paper identified an atmospheric circulation anomaly dipole structure anomaly in the Arctic atmosphere and its relationship with winter sea ice motion, based on the International Arctic Buoy Program (IABP) dataset (1979 98) and datasets from the National Centers for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) for the period 1960 2002. The dipole anomaly corresponds to the second-leading mode of EOF of monthly mean sea level pressure (SLP) north of 70ºN during the winter season (October March) and accounts for 13% of the variance. One of its two anomalous centers is stably occupied between the Kara Sea and Laptev Sea; the other is situated from the Canadian Archipelago through Greenland extending southeastward to the Nordic seas. The dipole anomaly differs from one described in other papers that can be attributed to an eastward shift of the center of action of the North Atlantic Oscillation. The finding shows that the dipole anomaly also differs from the 淏arents Oscillation revealed in a study by Skeie. Since the dipole anomaly shows a strong meridionality, it becomes an important mechanism to drive both anomalous sea ice exports out of the Arctic Basin and cold air outbreaks into the Barents Sea, the Nordic seas, and northern Europe.When the dipole anomaly remains in its positive phase, that is, negative SLP anomalies appear between the Kara Sea and the Laptev Sea with concurrent positive SLP over from the Canadian Archipelago extending southeastward to Greenland, there are large-scale changes in the intensity and character of sea ice transport in the Arctic basin. The significant changes include a weakening of the Beaufort gyre, an increase in sea ice export out of the Arctic basin through Fram Strait and the northern Barents Sea, and enhanced sea ice import from the Laptev Sea and the East Siberian Sea into the Arctic basin. Consequently, more sea ice appears in the Greenland and the Barents Seas during the positive phase of the dipole anomaly. During the negative phase of the dipole anomaly, SLP anomalies show an opposite scenario in the Arctic Ocean and its marginal seas when compared to the positive phase, with the center of negative SLP anomalies over the Nordic seas. Correspondingly, sea ice exports decrease from the Arctic basin flowing into the Nordic seas and the northern Barents Sea because of the strengthened Beaufort gyre.The finding indicates that influences of the dipole anomaly on winter sea ice motion are greater than that of the winter AO, particularly in the central Arctic basin and northward to Fram Strait, implying that effects of the dipole anomaly on sea ice export out of the Arctic basin become robust. The dipole anomaly is closely related to atmosphere ice ocean interactions that influence the Barents Sea sector.

Zhang L. P., T. L. Delworth, 2015: Analysis of the characteristics and mechanisms of the pacific decadal oscillation in a suite of coupled models from the geophysical fluid dynamics laboratory.J. Climate,28,7678-7701, https://doi.org/10.1175/JCLI-D-14-00647.1.

10.1175/JCLI-D-14-00647.1

042becd83b9cb473ec9bbaadf631d11b

http%3A%2F%2Fadsabs.harvard.edu%2Fabs%2F2015JCli...28.7678Z

http://journals.ametsoc.org/doi/10.1175/JCLI-D-14-00647.1North Pacific decadal oceanic and atmospheric variability is examined in a suite of coupled climate models developed at the Geophysical Fluid Dynamics Laboratory (GFDL). The models have ocean horizontal resolutions ranging from 1º to 0.1º and atmospheric horizontal resolutions ranging from 200 to 50 km. In all simulations the dominant pattern of decadal-scale sea surface temperature (SST) variability over the North Pacific is similar to the observed Pacific decadal oscillation (PDO). Simulated SST anomalies in the Kuroshio-Oyashio Extension (KOE) region exhibit a significant spectral peak at approximately 20 yr. Sensitivity experiments are used to show that (i) the simulated PDO mechanism involves extratropical air-sea interaction and oceanic Rossby wave propagation; (ii) the oscillation can exist independent of interactions with the tropics, but such interactions can enhance the PDO; and (iii) ocean-atmosphere feedback in the extratropics is critical for establishing the approximately 20-yr time scale of the PDO. The spatial pattern of the PDO can be generated from atmospheric variability that occurs independently of ocean-atmosphere feedback, but the existence of a spectral peak depends on active air-sea coupling. The specific interdecadal time scale is strongly influenced by the propagation speed of oceanic Rossby waves in the subtropical and subpolar gyres, as they provide a delayed feedback to the atmosphere. The simulated PDO has a realistic association with precipitation variations over North America, with a warm phase of the PDO generally associated with positive precipitation anomalies over regions of the western United States. The seasonal dependence of this relationship is also reproduced by the model.