Summary of Current Research

My research is focused on understanding climate change and the composition of the atmosphere (e.g. dust and pollution) over the past 100,000 years. Most of my current fieldwork is done on glaciers and ice sheets at polar latitudes and high altitudes collecting ice cores and snow samples for geochemical analyses (major [IC] and trace elements [ICP-MS, TIMS], stable isotopes [IRMS, TIMS]), and meteorological and geophysical data. However, I have also worked in the marine rhelm collecting marine geophysical data and sediment cores. Nearly all of this work represents collaborative efforts with many people, particularly with colleagues at Dartmouth College (Sharma, Jackson), the University of Maine (Mayewski, Kreutz, Koons, Handley, Sneed), the University of New Hampshire (Wake), the Geological Survey of Canada (Fisher, Zdanowicz, Zheng, Demuth), and the University of Otago (Koons, Landis, Upton). The majority of the research described below has been funded by the National Science Foundation Office of Polar Programs, and the National Oceanic and Atmospheric Administration .

Late Holocene Climate Variability

We have been investigating annual to centennial-scale climate variability over the past several thousand years in the North Pacific using ice cores collected from the St. Elias Range (Mt. Logan, Yukon, Canada) and the Alaska Range (Denali, Alaska, USA). Much of this research is focused on the behavior and forcing mechanisms of the Aleutian Low Pressure Center, which is the dominant wintertime climatological feature in the North Pacific. We use major ion, trace element, and stable isotope measurements from the ice cores to develop calibrated proxies of the Aleutian Low, annual precipitation rate, moisture source, temperature, and other climatological features that extend well beyond the instrumental record. Using statistical tools, we then compare our ice core paleoproxy records to other regional proxy records from tree rings, marine and lake cores, corals, etc. to understand the regional patterns of North Pacific climate variability. We have found that the El Nio-Southern Oscillation has a dramatic impact on the climate of this region, with an important contribution from solar variability. Understanding these natural influences on North Pacific climate are essential for determining the full extent of the dramatic human-caused climate change (warming) in this region over the past few decades. We have submitted a proposal to collect a deep ice core (500+ years long) from Denali to improve our understanding of recent North Pacific climate change.

Publications: Fisher et al., 2004; Fisher et al., 2008; Osterberg et al., under review (Climate Dynamcs);

Abstracts: Osterberg et al., 2008Osterberg et al., 2007; Kreutz et al., 2007; Osterberg et al, 2006; Kreutz et al., 2006; Yalcin et al., 2006;

Trends and Sources of trans-Pacific Pollution

Ice core records from Greenland, the Candian Arctic, and the European Alps show conclusively that heavy metal (Hg, Pb, Cd, Cu, Zn), SOx and NOx pollution have risen dramatically from natural, pre-anthropogenic levels to modern polluted levels due primarily to fossil fuel combustion and industrial smelting. Most of these atmospheric pollutants peaked in concentration in the early 1970s and have been declining ever since due to the adoption of pollution abatement legislation in North American and Western European naitons (e.g. US Clean Air Act, 1970). Rapidly developing nations in Asia, however, have not been as agressive in curbing their emissions and consequently they currently represent the largest emitters of most pollutants in the world today (Pacyna and Pacyna, 2001). Prevailing westerly winds in the mid-latitudes carries these pollutants across the Pacific to North America. We have used ice core records from the Saint Elias Mountains to show that emissions of Pb, As, and Bi (and likely Cu, Cs, and Zn) have been rising since the 1970s due to trans-Pacific pollution, contrasting dramatically with the pollution trends in the North Atlantic region. We are currently expanding our measurements to include mercury concentrations and Pb isotopes to further constrain North Pacific pollution sources, and we hope to collect a long pollution record from Denali to further investigate vertical and spatial gradiants in pollution levels and sources.

Publications: Osterberg et al., 2008; Osterberg et al., under review (EPSL); Kaspari et al., under review (JGR)

Abstracts: Osterberg et al., 2005, Kaspari et al., 2006 , Osterberg et al., 2006 (BIOGEOMON) 

Rapid Climate Change from D-O Events to the Little Ice Age

Paleoclimate records have demonstrated conclusively that the climate system is capable of abrubt, dramatic changes over mere years to decades. This has clear implications for understanding the potential for rapid climate change in a future world forced by higher anthropogenic CO2. The most dramatic example of rapid climate change is the glacial-age (30,000-70,000 years BP) Dansgaard-Oeschger Events recorded in the GISP2 ice core and elsewhere. We have re-analyzed sections of the GISP2 core at higher temporal resolution (2.5 years vs original 20 years) and for a larger suite of elements to better understand the timing and signature of these events. The so-called Little Ice Age is a much smaller rapid climate change event, but as the most recent example of an RCC, it offers an oppotunity to understand the forcing mechanisms of these events from a more diverse range of paleoproxies. We have been investigating the signature and forcing mechamisms of the LIA in the North Atlantic, North Pacific, and Antarctic regions using ice core records from Greenland, the Saint Elias Range, and West Antarctica. We are focusing particularly on the influence of solar irradiance changes, and the interplay between the global events and regionally important ocean-atmosphere oscillations such as the El Nio-Southern Oscillation, and the Northern and Southern Annual Modes (a.k.a. Arctic and Antarctic Oscillations).

Publications: Osterberg et al., under review (Climate Dynamics); Osterberg et al., in prep (GRL)

Ultra-Clean Ice Core Melting and Analysis

Much of my research is based on ultra-low level geochemical analyses from ice cores and snow samples. In order to obtain reliable data for these analyses, we have developed new, state-of-the-art ice core sampling and melting techniques that provide continuous, high-resolution samples (~1 cm core per sample standard; 0.2 cm core per sample possible) from the pristine ice core meltwater stream. These samples are suitable for anaylsis of trace element concentrations and isotope ratios at polar (very low) levels. This technology was developed in conjunction with the University of Maine Advanced Manufacturing Center (Orono, ME) and Advanced Machining and Tooling (Poway, CA). We have provided this technology at cost to colleagues in Canada, Japan, China, New Zealand, Australia, and Switzerland. Please contact me if you would like more information about the ice core melter system or how to obtain a system.

Publications: Osterberg et al., 2006

Abstracts: Osterberg et al., 2004

Marine and Glacial Geophysics

I used marine seismic reflection (boomer) techniques, side-scan sonar, and sediment cores to investigate the late Quaternary evolution of the Otago margin, New Zealand, for my Masters thesis. I focused this research on understanding late Quaternary sea-level on the Otago margin by using sequence stratigraphic techniques to identify depth-limited deposits and paleo-shorelines. I also worked with Dr. Upton (GNS; formally U. Otago) to profile lake Tekapo in the South Island, NZ to understand the structural regime and seismic history of the region. I have continued my interests in geophysics in the polar regions by using ice penetrating radar systems to understand alpine glacier flow in order to identify good ice core locations. Recently, I have been working with a student using ice penetrating radar to determine the volume of Peyto Glacier (Banff National Park, Canada) and determine the recent history of volume change under a warming climate regime.

Publications: Osterberg, 2006, Upton and Osterberg, 2007

Abstracts: Osterberg et al., 2001