Kaplan Yalcin

Anthropogenic signals recorded in an ice core from Eclipse Icefield, Yukon Territory, Canada

Trends in the annual flux of sulfate and nitrate in a new ice core collected at an elevation of 3017 m on Eclipse Icefield, 45 km northeast of Mt. Logan were examined to determine the effect of anthropogenic activity on precipitation chemistry in the remote northwest North American mid- troposphere. The annual flux of both sulfate and nitrate at Eclipse began increasing in the 1940s, demonstrating, for the first time, the anthropogenic sulfate and nitrate pollution of the northwest North American Arctic in an ice core from this region. Comparison of the Eclipse record with regional emission estimates for total sulfur and nitrogen oxides suggests that Eurasia is the dominant source of pollutants reaching Eclipse. The available data does not permit a confident assessment of the relative importance of European versus Soviet emissions in producing the observed trends in sulfate and nitrate at Eclipse.

The climate signal recorded in the oxygen-isotope, accumulation and major-ion time series from the Eclipse ice core,YukonTerritory, Canada

Abstract The high accumulation rate, nearly complete preservation and detailed chronology of the Eclipse ice core, Yukon Territory, Canada, are well suited for comparison of the glaciochemical recordwith instrumental time series of temperature, precipitation and sea-level pressure. Results of cross-correlation analysis of instrumental temperature records with the Eclipse δ18O time series reveal a significant positive relationship between summertime δ18O at Eclipse and summer (April–September) temperatures in northwestern North America. the results indicate that the Eclipse δ18O time series provides a better proxy for regional temperature than does the δ18O time series from the Mount Logan ice-core record for which only negative correlations were found. Winter accumulation at Eclipse is significantly correlated with several sites in Alaska, but not with any sites in the Yukon. the δ18O, accumulation and glaciochemical time series also display significant correlations with the Northern Hemisphere sea-level pressure dataset, especially between wintertime sulfate and nitrate concentrations at Eclipse and the intensity of the wintertime Siberian high and Aleutian and Icelandic lows. These results suggest that year-to-year variability in the deposition of pollutants at Eclipse can be linked to changes in atmospheric circulation, while long-term trends can be explained by changes in source strength.

A 1000-yr record of forest fire activity from Eclipse icefield, Yukon, Canada

A 1000-yr record of forest fire activity has been developed using three annually dated ice cores from Eclipse Icefield, Yukon, Canada. Forest fire signals were identified as NH4 plus residuals above a robust spline and corroborated by an empirical orthhogonal function (EOF) analysis that identified a chemical association in the NH4 plus, C204 2 macr and Kplus records similar to that observed in forest fire plumes. These statistical techniques yielded similar records of forest fire activity, although the EOF analysis provides more conservative identification of forest fire signals. Comparison of forest fire signals in the Eclipse ice cores with the record of annual area burned in Alaska and the Yukon demonstrates that 80% of high fire years in Alaska and 79% of high fire years in the Yukon are identifiable as NH4 plus concentration residuals in at least one core from Eclipse Icefield, although any individual core records 36-67% of these events. The Eclipse ice cores record high fire activity in the AD 1760s, 1780s, 1840s, 1860s, 1880s, 1890s, 1920s-1940s and 1980s. Peak fire activity occurred in the 1890s, possibly reflecting anthropogenic ignition sources associated with the large influx of people to the Yukon during the Klondike Gold Rush. Periods of low fire activity are evident during the 1770s, 181Os-1830s, 1850s, 1950s and 1960s. Extending our proxy of fire activity to AD 1000 using annual NH4 plus concentrations from our one core that extends back this far provides evidence of high fire activity from 1240 to 1410 during the waning stages of the ‘Mediaeval Warm Period’.

A 100‐year record of North Pacific volcanism in an ice core from Eclipse Icefield, Yukon Territory, Canada

Iceland, and the 1989 Redoubt, Alaska, eruptions. Non-sea-salt SO4 2 residuals above a robust spline and empirical orthogonal function (EOF) analysis were used to identify volcanic SO4 2 signatures. Volcanic sulfate values are more conservatively identified by the EOF analysis as sulfate deposition from other sources is more robustly accounted for. Some eruptions are also recorded as peaks in non-sea-salt chloride. The volcanic signals in the Eclipse ice core are mostly attributable to Alaskan, Aleutian, or Kamchatkan eruptions. Conversely, the Eclipse ice core provides a poor record of globally significant tropical eruptions. These results are promising for the development of longer ice core based records of paleovolcanism in the North Pacific rim. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0370 Atmospheric Composition and Structure: Volcanic effects (8409); 8409 Volcanology: Atmospheric effects (0370); KEYWORDS: Yukon Territory, ice cores, volcanism, atmospheric effects, Kamchatka, Alaska

Constraining recent lead pollution sources in the North Pacific using ice core stable lead isotopes

[1] Trends and sources of lead (Pb) aerosol pollution in the North Pacific rim of North America from 1850 to 2001 are investigated using a high-resolution (subannual to annual) ice core record recovered from Eclipse Icefield (3017 masl; St. Elias Mountains, Canada). Beginning in the early 1940s, increasing Pb concentration at Eclipse Icefield occurs coevally with anthropogenic Pb deposition in central Greenland, suggesting that North American Pb pollution may have been in part or wholly responsible in both regions. Isotopic ratios ( 208 Pb/ 207 Pb and 206 Pb/ 207 Pb) from 1970 to 2001 confirm that a portion of the Pb deposited at Eclipse Icefield is anthropogenic, and that it represents a variable mixture of East Asian (Chinese and Japanese) emissions transported eastward across the Pacific Ocean and a North American component resulting from transient meridional atmospheric flow. Based on comparison with source material Pb isotope ratios, Chinese and North American coal combustion have likely been the primary sources of Eclipse Icefield Pb over the 1970–2001 time period. The Eclipse Icefield Pb isotope composition also implies that the North Pacific mid-troposphere is not directly impacted by transpolar atmospheric flow from Europe. Annually averaged Pb concentrations in the Eclipse Icefield ice core record show no long-term trend during 1970–2001; however, increasing 208 Pb/ 207 Pb and decreasing 206 Pb/ 207 Pb ratios reflect the progressive East Asian industrialization and increase in Asian pollutant outflow. The post-1970 decrease in North American Pb emissions is likely necessary to explain the Eclipse Icefield Pb concentration time series. When compared with low (lichen) and high (Mt. Logan ice core) elevation Pb data, the Eclipse ice core record suggests a gradual increase in pollutant deposition and stronger trans-Pacific Asian contribution with rising elevation in the mountains of the North Pacific rim.

Eclipse Ice Core Accumulation and Stable Isotope Variability as an Indicator of North Pacific Climate

AbstractThe high accumulation rate and negligible amount of melt at Eclipse Icefield (3017 m) in the Saint Elias Range of Yukon, Canada, allows for the preservation of a high-resolution isotopic and glaciochemical records valuable for reconstruction of climatic variables. Each of the three Eclipse ice cores have a well-constrained depth–age scale with dozens of reference horizons over the twentieth century that permits an exceptional level of confidence in the results of the current calibration exercise. Stacked time series of accumulation and stable isotopes were divided into cold and warm seasons and seasons of extreme high and extreme low accumulation and stable isotope values (eight groups). For each group, season-averaged composites of 500-hPa geopotential height grids, and the individual seasons that constitute them, were analyzed to elucidate common anomalous flow patterns.This analysis shows that the most fractionated isotopes and lowest accumulation cold seasons reflect a more zonal height patter...