Thomas J. Ballinger

Climatic and atmospheric teleconnection indices and western Arctic sea ice variability

This 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 176º W to 126º W 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° W in the Chukchi Sea, mostly by NHTs. With the exception of the three easternmost longitudes (136–126° W), 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.

Overlap of global Köppen–Geiger climates, biomes, and soil orders

Climate types, biome types, and soil orders are commonly used among physical geographers in research and to describe natural environmental characteristics. However, little attempt has been made to quantify the percentage of global land surface that is covered by combinations of climate types, biomes, and soil orders. This research overlays a world map of 31 climate types produced based on the Köppen–Geiger criteria using gridded NCAR/NCEP reanalysis monthly mean surface air temperature and precipitation data from 1981 to 2010 with global maps of eight biomes adapted from World Wildlife Federation and 12 soil orders from United States Natural Resources Conservation Service. Areas covered by each of the 2976 combinations are then calculated. Results suggest that, as expected, a few climate/biome/soil combinations are most common, such as desert climate/desert biome/entisols, tundra climate/tundra biome/gelisols, and desert climate/desert biome/aridisols. The local nature of soil properties causes small enclaves of unexpected combinations of climate, biome, and soils, and the 10 most extensive climate/biome/soil combinations occupy only one-quarter of the global land surface. The strong correspondence between climate and biome types validates the Köppen–Geiger criteria for categorizing climates based on vegetation realms, even today, despite the general paucity of data available when the criteria were established.

Spatiotemporal analysis of the January Northern Hemisphere circumpolar vortex over the contiguous United States

January 2014 will be remembered for the sensationalized media usage of the term “polar vortex” which coincided with several polar air outbreaks. A United States polar vortex (USPV) perspective is presented to better understand the January spatial and temporal variability of this regional component of the Northern Hemisphere circumpolar vortex. Use of the monthly mean 5460 m isohypse to represent the location of the USPV extent and area revealed that the spatial features of the January 2014 USPV were not extreme relative to certain 1948–2013 Januaries. Furthermore, the Arctic Oscillation (AO), Pacific-North American (PNA) Pattern, and Pacific Decadal Oscillation (PDO) are all linked to southernmost latitude of the USPV trough, but the PDO and PNA are most closely associated with the longitude at which this latitude occurs. The AO is closely related to the area of the United States enclosed within the USPV.

The Polar Marine Climate Revisited

AbstractAs an additional classification to Koppen’s climate classification for polar (E) climates, the Polar Marine (EM) climate was presented nearly five decades ago and is revisited in this paper. The EM climate was traced to the North Atlantic, North Pacific, and Southern Ocean and recognized as wet, cloudy, and windy, especially during winter. These areas by definition are encompassed by monthly mean air temperatures of −6.7°C (20°F) and 10°C (50°F) in the coldest and warmest months of the annual cycle, respectively. Here three global reanalyses [ECMWF Interim Re-Analysis (ERA-Interim), Climate Forecast System Reanalysis (CFSR), and Japan Meteorological Agency (JMA) 25-yr reanalysis (JRA-25)] are used to produce a modern depiction of EM climate. General agreement is found between original and new EM boundaries, for which the poleward boundary can be approximated by the winter sea ice maximum and the equatorward boundary by the warmest month SSTs. Variability of these parameters is shown to largely dic...

Recent increased warming of the Alaskan marine Arctic due to midlatitude linkages

Alaskan Arctic waters have participated in hemispheric-wide Arctic warming over the last two decades at over two times the rate of global warming. During 2008–13, this relative warming occurred only north of the Bering Strait and the atmospheric Arctic front that forms a north–south thermal barrier. This front separates the southeastern Bering Sea temperatures from Arctic air masses. Model projections show that future temperatures in the Chukchi and Beaufort seas continue to warm at a rate greater than the global rate, reaching a change of +4°C by 2040 relative to the 1981–2010 mean. Offshore at 74°N, climate models project the open water duration season to increase from a current average of three months to five months by 2040. These rates are occasionally enhanced by midlatitude connections. Beginning in August 2014, additional Arctic warming was initiated due to increased SST anomalies in the North Pacific and associated shifts to southerly winds over Alaska, especially in winter 2015–16. While global warming and equatorial teleconnections are implicated in North Pacific SSTs, the ending of the 2014–16 North Pacific warm event demonstrates the importance of internal, chaotic atmospheric natural variability on weather conditions in any given year. Impacts from global warming on Alaskan Arctic temperature increases and sea-ice and snow loss, with occasional North Pacific support, are projected to continue to propagate through the marine ecosystem in the foreseeable future. The ecological and societal consequences of such changes show a radical departure from the current Arctic environment.摘要过去二十年来, 阿拉斯加北极海域参与了北极半球尺度的增暖, 其增暖速率达到了全球增暖速率的两倍多. 在2008年至2013年期间, 这种相对增暖主要发生在白令海峡和形成南北热力屏障的北极锋区以北. 这一锋区将东南部的白令海温度与北极气团分隔开. 数值模式的预测结果表明, 楚科奇海和博福特海未来将继续以高于全球速率的水平增暖. 到2040年, 该地区的温度相对于1981-2010年的平均值将高出 4°C. 气候模式还预测, 在74°N海面上的开放水域持续时间将从目前的平均3个月增加到2040年的5个月. 这些增速有时会因中纬度的相关而增强. 从2014年8月开始, 北极增暖的进一步加剧始于北太平洋的海面温度(SST)异常增暖, 并伴随着阿拉斯加上方相应转变的南风导致, 特别是2015-16年冬季. 虽然全球增暖和赤道遥相关主要影响北太平洋海温, 但2014-16北太平洋增暖事件的结束表明了在任何一年混沌的大气内部自然变率对天气的重要性. 在可预见的未来, 伴随着北太平洋偶尔的支持, 全球变暖对阿拉斯加的温度增加和北极海冰和积雪减少的影响将继续通过海洋生态系统传播. 这种变化的生态和社会后果将显示出与当前北极环境的根本偏离.

Subseasonal atmospheric regimes and ocean background forcing of Pacific Arctic sea ice melt onset

One observed fingerprint of Pacific Arctic environmental change, induced by climate warming and amplified local feedbacks, is a shift toward earlier onset of sea ice melt. Shorter freeze periods impact the melt season energy balance with cascading effects on ecological productivity and human presence in the region. Through this study, a non-linear technique, self-organizing maps, is utilized to investigate the subseasonal role of regional pressure patterns and associated lower-tropospheric wind regimes on melt onset in the Beaufort and Chukchi Seas. Focus is directed on the frequency and duration (≥ 3 consecutive days) of offshore, onshore, and zonal/weak flow that tend to precede anomalous (late and early) and average times of melt. Background North Pacific climate forcing ascribed from the Pacific Decadal Oscillation (PDO) phase and Bering Strait oceanic heat flux measurements provide a surface thermal context to the composite wind fields. In early melt onset years, onshore (northerly) winds occur approximately 1–3 fewer days with offsetting increases in zonal and offshore flow in the Beaufort and Chukchi Seas. During these cases, the Beaufort High pattern tends to set-up more frequently around the southeastern Beaufort Sea region, yielding winds of a southerly and/or easterly nature that are enhanced by cyclone activity to the south or downstream. Chukchi Sea weather analyses, in particular, suggest that interacting, precursor mechanisms involving warm air advection off snow-free Arctic lands and from southerly latitudes coupled with a slightly positive PDO state and anomalous, poleward oceanic heat transfer condition the seasonal ice pack for increasingly early melt.

Anomalous blocking over Greenland preceded the 2013 extreme early melt of local sea ice

ABSTRACT The Arctic marine environment is undergoing a transition from thick multi-year to first-year sea-ice cover with coincident lengthening of the melt season. Such changes are evident in the Baffin Bay-Davis Strait-Labrador Sea (BDL) region where melt onset has occurred ~8 days decade−1 earlier from 1979 to 2015. A series of anomalously early events has occurred since the mid-1990s, overlapping a period of increased upper-air ridging across Greenland and the northwestern North Atlantic. We investigate an extreme early melt event observed in spring 2013. (~6σ below the 1981–2010 melt climatology), with respect to preceding sub-seasonal mid-tropospheric circulation conditions as described by a daily Greenland Blocking Index (GBI). The 40-days prior to the 2013 BDL melt onset are characterized by a persistent, strong 500 hPa anticyclone over the region (GBI >+1 on >75% of days). This circulation pattern advected warm air from northeastern Canada and the northwestern Atlantic poleward onto the thin, first-year sea ice and caused melt ~50 days earlier than normal. The episodic increase in the ridging atmospheric pattern near western Greenland as in 2013, exemplified by large positive GBI values, is an important recent process impacting the atmospheric circulation over a North Atlantic cryosphere undergoing accelerated regional climate change.