Summary of Current Research

My overarching research objective is to understand the past natural variability, dynamics, and forcing mechanisms of the atmosphere and cryosphere, to more accurately quantify the impact of human activities on these interrelated systems. My specialty is developing geochemical paleoclimate and paleoatmosphere records using ice cores from ice sheets and mountain glaciers. I utilize several analytical techniques (ICP-MS, IC, IRMS, TIMS) to determine the concentrations and isotopic ratios of atmospheric aerosols (e.g. dust, sea salt, pollution) trapped in ice cores, and of the ice itself (δ¹⁸O). I then develop these glaciochemical time series into statistically robust paleoproxy records of climate variables (e.g. temperature, precipitation) and forcing mechanisms (e.g. solar variability, volcanic activity), and human pollution trends and sources. Nearly all of this work represents collaborative efforts with many people, particularly with colleagues at Dartmouth College (Sharma, Hawley, Kelly, Jackson), the University of Maine (Mayewski, Kreutz, Koons, Handley, Sneed, Birkel), the University of New Hampshire (Wake, Courville, Licciardi), the Geological Survey of Canada (Fisher, Zdanowicz, Zheng, Demuth), and the University of Otago (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 in the Arctic and North Pacific

We have been investigating annual to centennial-scale climate (temperature, precipitation, atmospheric circulation) variability over the past several thousand years in the North Pacific using ice cores collected from the St. Elias Range (Mt. Logan and Eclipse Icefield, 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 climatological feature in the region (see fig to right).  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 recently (October, 2010) submitted a multi-disciplinary proposal to collect 2,000+ year-long ice core records and glacial moraine exposure age dates from Denali National Park, and conduct glacial modeling experiments to improve our understanding of central Alaskan hydroclimate change, glacier response, and sea level contribution.

Publications: Kelsey et al., 2010; Fisher et al., 2004; Fisher et al., 2008; Osterberg et al., under review (Climate Dynamcs);

Abstracts: Winski et al., 2010; Kreutz et al., 2009; Kelsey et al., 2009; Osterberg et al., 2008; Osterberg et al., 2007; Kreutz et al., 2007; Osterberg et al, 2006; Kreutz et al., 2006; Yalcin et al., 2006;

Trends and Sources of Atmospheric Pollution

Ice core records from Greenland, the Canadian Arctic, and the European Alps show conclusively that heavy metal (Hg, Pb, Cd, Cu, Zn), SOx and NOx pollution have risen dramatically from low natural 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 nations (e.g. 1970 Clean Air Act). However, our ice core records from the Saint Elias Mountains show that North Pacific levels of Pb, As, and Bi have been rising since the 1970s due to trans-Pacific pollution from Asia, contrasting dramatically with the pollution trends in the North Atlantic region.

We have also been investigating the hypothesis that the modern atmosphere is contaminated with anthropogenic Os from the smelting of platinum group elements primarily for catalytic converters (e.g. Chen et al., 2009). To test this hypothesis, we are developing the first polar time series of Os concentration and isotopic composition using an ice core collected from Summit, Greenland in 2010.

Publications: Kaspari et al., 2009;  Osterberg et al., 2008; Norton et al., 2007; Osterberg et al., in final prep (EPSL)

Abstracts: Osterberg et al., 2010; Beal et al., 2010; Osterberg et al., 2009; Kreutz et al., 2009; Osterberg et al., 2005, Kaspari et al., 2006 , Osterberg et al., 2006 (BIOGEOMON) 

Spatial Variability of Physical and Chemical Firn Properties, Northern Greenland

The Greenland Ice Sheet (GIS) is a key component in the effort to understand climate change. The two key questions that must be asked in any assessment of the state of an ice sheet are: "What has it been doing in the past?" and "What is it doing right now?"  This new project seeks to help answer these two defining questions by investigating the physical and chemical properties of surface and near-surface snow and firn along a traverse from Thule, North coastal Greenland, to Summit camp, central Greenland. We are collecting and analyzing a series of firn cores and snow pit samples in 2010 and 2011 to investigate the impact of changing temperature and accumulation rate on the ice sheet from the northwest coast to the ice divide.

Abstracts: Wong et al., 2010

Glacial and Marine Geophysics

I use ice (ground) penetrating radar systems (GPR) and global positioning system (GPS) data to understand alpine glacier geometry and flow dynamics (e.g. Denali region), and snow accumulation variability (e.g. Greenland).  I have also been working with Dom Winski (student) and Dr. Hawley 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. This work stems from my Masters thesis research offshore New Zealand, where 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. I focused this research on understanding late Quaternary sea level on the Otago margin by using sequence stratigraphic techniques to identify 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.

Publications: Osterberg, 2006; Upton and Osterberg, 2007; Campbell et al., 2010a; Campbell et al., 2010b

Abstracts: Campbell et al., 2010; Hawley et al., 2009; Campbell et al., 2009; Osterberg et al., 2001

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 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 Niño-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