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Doctoral thesis. Large-scale reductions in ice concentration appear to be common in the Canadian Arctic basin. The development of these features, which may have some important climatic and oceanographic implications, can often be explained from simple dynamical considerations.
The Arctic has been undergoing significant changes in recent years. Average temperatures are rising twice as fast as they are elsewhere in the world. The extent and thickness of sea ice is rapidly declining. Such changes may have an impact on atmospheric conditions outside the region. Several hypotheses for how Arctic warming may be influencing mid-latitude weather patterns have been proposed recently. For example, Arctic warming could lead to a weakened jet stream resulting in more persistent weather patterns in the mid-latitudes. Or Arctic sea ice loss could lead to an increase of snow on high-latitude land, which in turn impacts the jet stream resulting in cold Eurasian and North American winters. These and other potential connections between a warming Arctic and mid-latitude weather are the subject of active research. Linkages Between Arctic Warming and Mid-Latitude Weather Patterns is the summary of a workshop convened in September 2013 by the National Research Council to review our current understanding and to discuss research needed to better understand proposed linkages. A diverse array of experts examined linkages between a warming Arctic and mid-latitude weather patterns. The workshop included presentations from leading researchers representing a range of views on this topic. The workshop was organized to allow participants to take a global perspective and consider the influence of the Arctic in the context of forcing from other components of the climate system, such as changes in the tropics, ocean circulation, and mid-latitude sea surface temperature. This report discusses our current understanding of the mechanisms that link declines in Arctic sea ice cover, loss of high-latitude snow cover, changes in Arctic-region energy fluxes, atmospheric circulation patterns, and the occurrence of extreme weather events; possible implications of more severe loss of summer Arctic sea ice upon weather patterns at lower latitudes; major gaps in our understanding, and observational and/or modeling efforts that are needed to fill those gaps; and current opportunities and limitations for using Arctic sea ice predictions to assess the risk of temperature/precipitation anomalies and extreme weather events over northern continents.
Recent well documented reductions in the thickness and extent of Arctic sea ice cover, which can be linked to the warming climate, are affecting the global climate system and are also affecting the global economic system as marine access to the Arctic region and natural resource development increase. Satellite data show that during each of the past six summers, sea ice cover has shrunk to its smallest in three decades. The composition of the ice is also changing, now containing a higher fraction of thin first-year ice instead of thicker multi-year ice. Understanding and projecting future sea ice conditions is important to a growing number of stakeholders, including local populations, natural resource industries, fishing communities, commercial shippers, marine tourism operators, national security organizations, regulatory agencies, and the scientific research community. However, gaps in understanding the interactions between Arctic sea ice, oceans, and the atmosphere, along with an increasing rate of change in the nature and quantity of sea ice, is hampering accurate predictions. Although modeling has steadily improved, projections by every major modeling group failed to predict the record breaking drop in summer sea ice extent in September 2012. Establishing sustained communication between the user, modeling, and observation communities could help reveal gaps in understanding, help balance the needs and expectations of different stakeholders, and ensure that resources are allocated to address the most pressing sea ice data needs. Seasonal-to-Decadal Predictions of Arctic Sea Ice: Challenges and Strategies explores these topics.
"The relationship between Arctic sea ice concentration anomalies, particularly those associated with the "Great Salinity Anomaly" of 1968-1982, and atmospheric circulation anomalies is investigated. Empirical orthogonal function (EOF) analyses are performed on winter and summer sea ice concentrations, sea-level pressure, 500 hPa heights and 850 hPa temperatures: these data cover the Northern Hemisphere north of 45$ sp circ$N during the post-World War II era. Spatial maps of temporal correlation coefficients between EOF 1 of winter sea ice concentration and the atmospheric anomaly fields are calculated. Significant correlations (at 95 and 99% levels) were found to exist between EOF 1 of winter sea ice and the atmospheric anomaly fields at zero lag, and with ice leading by one and one-and-a-half years, and ice lagging by one year. The main emphasis of the thesis is to identify connections between Arctic sea ice and atmospheric circulation anomalies at interannual timescales." --
Freeze-up at Alert, Eureka, Isachsen, Mould Bay, and Resolute in the Canadian Arctic was observed to occur any time between the last week in August and the last week in September. A mathematical relationship between air temperature and sea-ice formation provided a favorable method for predicting the date of freeze-up at these stations. The maximum seasonal growth of sea ice, 269 cm, was measured at Isachsen; the minimum, 149 cm, was measured at Resolute. These values are based on measurements made at the five stations in the Canadian Arctic Archipelago having a total of 35 station years of record. Equations to predict the growth of sea ice by increments were derived empirically from the observations made at these locations. A separate term is introduced in the equations to take account of the effects of snow-cover depths on ice growth. To apply the formulas only air-temperature and snow-depth data are required. The study disclosed good correlation between air temperature and decrease in sea-ice thickness at the Arctic stations. The relationship was found to be: h = 0.55 sigma theta where h = decrease in ice thickness (cm) and sigma theta = accumulated degree days (above -1.8C). (Author).
The Arctic climate has rapidly changed over the last several decades, especially across the western Arctic Ocean where dramatic alterations to the end-of-summer sea ice extent and autumn freeze-up have been observed. While the spatiotemporal patterns of sea ice variability are well-documented by modern satellite instrumentation, the regional atmospheric causes and subsequent consequences of sea ice changes over this portion of the Arctic remain unclear. This dissertation research utilizes synoptic climatological techniques to evaluate the aforementioned sea ice-climate interactions in the western Arctic and high latitude North America since 1979. Separate atmospheric pattern classifications comprised of daily mean, gridded, sea level pressure and 1000-500 hPa thickness data are developed and associated with the western Arctic September sea ice minima and the timing of continuous autumn freeze-up. Data from a weather typing scheme known as the Spatial Synoptic Classification (SSC) is also employed to holistically evaluate near-surface temperature and moisture changes during the autumn and winter months, as indicated by the anomalous occurrences of the dominant SSC weather types (Dry Polar (DP) and Moist Polar (MP)) within those months, throughout the terrestrial North American Arctic that coincide with western Arctic sea ice freeze-up variability. Results suggest that recent summer increases in Beaufort Sea High pressure patterns, especially during June, play a significant, dynamic role in both the multidecadal and interannual end-of-summer ice extent losses and freeze-up delays witnessed in the region. The general persistence of ice cover formation later into autumn also parallels a transition of DP to MP weather types across much of Alaska and Yukon Territory during autumn and winter months over time. Future work will explore connections between sea ice cover variability, large-scale atmospheric circulation, and surface weather conditions across the Northern Hemisphere high and middle latitudes.