• Energy Research

This project intends to use the Mount Denali ice core archive to develop the most comprehensive suite of North Pacific fire and summer climate proxy records since about 2500 years before present. Wildfire is a key component of summer climate in the North Pacific where wildfires are projected to increase with continued summer warming. Studies that combine paleorecords of summer climate and wildfire are therefore critically needed, especially in the North Pacific region where fire recurrence rate and decadal-to-centennial scale climate fluctuations occur over longer time periods than are covered by direct observations. The goal of the proposed research is to improve our understanding of relationships between summertime climate and wildfire activity, focusing especially on the Medieval Climate Anomaly (MCA), when regional temperatures were perhaps as warm as the 20th century. Recent advances now permit the measurement of new fire-related (pyrogenic) compounds in ice cores, enabling the development of a robust fire record capable of rigorous comparison with regional paleoclimate reconstructions.

This project intends to use the Mount Denali ice core archive to develop the most comprehensive suite of North Pacific fire and summer climate proxy records since about 2500 years before present. Wildfire is a key component of summer climate in the North Pacific where wildfires are projected to increase with continued summer warming. Studies that combine paleorecords of summer climate and wildfire are therefore critically needed, especially in the North Pacific region where fire recurrence rate and decadal-to-centennial scale climate fluctuations occur over longer time periods than are covered by direct observations. The goal of the proposed research is to improve our understanding of relationships between summertime climate and wildfire activity, focusing especially on the Medieval Climate Anomaly (MCA), when regional temperatures were perhaps as warm as the 20th century. Recent advances now permit the measurement of new fire-related (pyrogenic) compounds in ice cores, enabling the development of a robust fire record capable of rigorous comparison with regional paleoclimate reconstructions.

AbstractUS maize and soy production have increased rapidly since the mid-20th century. While global warming has raised temperatures in most regions over this time period, trends in extreme heat have been smaller over US croplands, reducing crop-damaging high temperatures and benefiting maize and soy yields. Here we show that agricultural intensification has created a crop-climate feedback in which increased crop production cools local climate, further raising crop yields. We find that maize and soy production trends have driven cooling effects approximately as large as greenhouse gas induced warming trends in extreme heat over the central US and substantially reduced them over the southern US, benefiting crops in all regions. This reduced warming has boosted maize and soy yields by 3.3 (2.7–3.9; 13.7%–20.0%) and 0.6 (0.4–0.7; 7.5%–13.7%) bu/ac/decade, respectively, between 1981 and 2019. Our results suggest that if maize and soy production growth were to stagnate, the ability of the crop-climate feedback to mask warming would fade, exposing US crops to more harmful heat extremes.

This project intends to use the Mount Denali ice core archive to develop the most comprehensive suite of North Pacific fire and summer climate proxy records since about 2500 years before present. Wildfire is a key component of summer climate in the North Pacific where wildfires are projected to increase with continued summer warming. Studies that combine paleorecords of summer climate and wildfire are therefore critically needed, especially in the North Pacific region where fire recurrence rate and decadal-to-centennial scale climate fluctuations occur over longer time periods than are covered by direct observations. The goal of the proposed research is to improve our understanding of relationships between summertime climate and wildfire activity, focusing especially on the Medieval Climate Anomaly (MCA), when regional temperatures were perhaps as warm as the 20th century. Recent advances now permit the measurement of new fire-related (pyrogenic) compounds in ice cores, enabling the development of a robust fire record capable of rigorous comparison with regional paleoclimate reconstructions.

A major achievement in research supported by the Kluane Lake Research Station was the recovery, in 2001 – 02, of a suite of cores from the icefields of the central St. Elias Mountains, Yukon, by teams of researchers from Canada, the United States, and Japan. This project led to the development of parallel, long (103 – 104 year) ice-core records of climate and atmospheric change over an altitudinal range of more than 2 km, from the Eclipse Icefield (3017 m) to the ice-covered plateau of Mt. Logan (5340 m). These efforts built on earlier work recovering single ice cores in this region. Comparison of these records has allowed for variations in climate and atmospheric composition to be linked with changes in the vertical structure and dynamics of the North Pacific atmosphere, providing a unique perspective on these changes over the Holocene. Owing to their privileged location, cores from the St. Elias Icefields also contain a remarkably detailed record of aerosols from various sources around or across the North Pacific. In this paper we review major scientific findings from the study of St. Elias Mountain ice cores, focusing on five main themes: (1) The record of stable water isotopes (δ18O, δD), which has unique characteristics that differ from those of Greenland, other Arctic ice cores, and even among sites in the St. Elias; (2) the snow accumulation history; (3) the record of pollen, biomass burning aerosol, and desert dust deposition; (4) the record of long-range air pollutant deposition (sulphate and lead); and (5) the record of paleo-volcanism. Our discussion draws on studies published since 2000, but based on older ice cores from the St. Elias Mountains obtained in 1980 and 1996.

A high‐resolution, 8000 year‐long ice core record from the Mt. Logan summit plateau (5300 m asl) reveals the initiation of trans‐Pacific lead (Pb) pollution by ca. 1730, and a >10‐fold increase in Pb concentration (1981–1998 mean = 68.9 ng/l) above natural background (5.6 ng/l) attributed to rising anthropogenic Pb emissions from Asia. The largest rise in North Pacific Pb pollution from 1970–1998 (end of record) is contemporaneous with a decrease in Eurasian and North American Pb pollution as documented in ice core records from Greenland, Devon Island, and the European Alps. The distinct Pb pollution history in the North Pacific is interpreted to result from the later industrialization and less stringent abatement measures in Asia compared to North America and Eurasia. The Mt. Logan record shows evidence for both a rising Pb emissions signal from Asia and a trans‐Pacific transport efficiency signal related to the strength of the Aleutian Low.

Abstract The northeastern United States has experienced a large increase in precipitation over recent decades. Annual and seasonal changes of total and extreme precipitation from station observations in the Northeast were assessed over multiple time periods spanning 1901–2014. Spatially averaged, both annual total and extreme precipitation across the Northeast increased significantly since 1901, with changepoints occurring in 2002 and 1996, respectively. Annual extreme precipitation experienced a larger increase than total precipitation; extreme precipitation from 1996 to 2014 is 53% higher than from 1901 to 1995. Spatially, coastal areas receive more total and extreme precipitation on average, but increases across the changepoints are distributed fairly uniformly across the domain. Increases in annual total precipitation across the 2002 changepoint are driven by significant total precipitation increases in fall and summer, while increases in annual extreme precipitation across the 1996 changepoint are driven by significant extreme precipitation increases in fall and spring. The ability of gridded observed and reanalysis precipitation data to reproduce station observations was also evaluated. Gridded observations perform well in reproducing averages and trends of annual and seasonal total precipitation, but extreme precipitation trends show significantly different spatial and domain-averaged trends than station data. The North American Regional Reanalysis generally underestimates annual and seasonal total and extreme precipitation means and trends relative to station observations, and also shows substantial differences in the spatial pattern of total and extreme precipitation trends within the Northeast.