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Summary of Current Research:

Climate Change, Glacier Response, and Atmospheric Pollution

My overarching research objective is to understand how and why Earth’s environment changed in the past, and is changing today, so we can more accurately predict how it will change in the future. My specialty is developing records of past climate change and air pollution by analyzing chemical markers preserved in glacier ice cores. I am particularly interested in how glaciers responded to warm periods in the past, as this provides an example of how glaciers and sea level may respond to future global warming. Currently, my colleagues and I are investigating these problems through NSF-funded research projects in Greenland and the North Pacific region, including Alaska and the Yukon Territory.

Reconstructing Central Alaskan Precipitation Variability and Atmospheric Circulation over the Past Millennium

Funded by NSF P2C2 (AGS-1204035); Collaborators: Cameron Wake (UNH), Karl Kreutz (UMaine) and Sean Birkel (UMaine)

The main goal of this collaborative Dartmouth-UMaine-UNH project is to reconstruct the history of precipitation and atmospheric circulation in Alaska during the last thousand years using ice core records of snow accumulation. In May-June 2013, we collected two new ice cores to bedrock (208 m) from the Mt. Hunter Plateau in the Alaska Range of Denali National Park. These cores will be melted with our continuous ice core melter, and analyzed for chemical concentrations and stable water isotopes to reconstruct past snow accumulation and storminess. These new records will be combined with an existing spatial array of ice cores collected from the North Pacific region to map changes in the spatial patterns of precipitation through time. Because atmospheric circulation patterns such as El Niño and the Pacific Decadal Oscillation (PDO) have specific precipitation fingerprints (see figure), this spatial array of ice cores will provide a record of how these larger scale climate systems have varied during the last thousand years. The project will focus on determining the differences in Alaskan precipitation patterns during the Little Ice Age (approximately 200 to 600 years ago) and Medieval Climate Anomaly (approximately 800 to 1,200 years ago). Furthermore, we are collaborating with Joe Licciardi at UNH who will develop a chronology of the past advance and retreat of glaciers in Denali National Park, allowing us to understand their sensitivity to past climate change and thereby better predict future changes with global warming. Check out the story and pictures of our 2013 drilling season on Mt. Hunter.

Publications from this and earlier Denali NSF grant (ARC-0714004): Campbell et al., 2013; Campbell et al., 2012a; Winski et al., 2012; Campbell et al., 2012b; Kelsey et al., 2010

Response of the NW Greenland Cryosphere to Holocene Climate Change

Funded by NSF ANS (ARC-1107511); Collaborators: Meredith Kelly (Dartmouth), Yarrow Axford (Northwestern) and Sean Birkel (UMaine)

The aim of this collaborative project between investigators at Dartmouth, Northwestern and UMaine is to develop records of past climate in northwest (NW) Greenland and synthesize them with records of the ice margin position to evaluate the response of the Greenland Ice Sheet to past warm periods, such as the Holocene Climatic Optimum (approximately 5 to 9 thousand years ago). The proposed research integrates multiple climate proxies collected from the Thule region with glaciological modeling experiments to address the following research objectives: (1) reconstruct Holocene climate in NW Greenland via inferences from reconstructed local ice cap extents (North Ice Cap, Tuto Ice Cap), ice core stable isotope and precipitation records, and data from nearby lake sediments; (2) Examine the sensitivity of the NW Greenland Ice Sheet (GIS) to Holocene climate changes by developing the history of the areal extent of the GIS and synthesizing proxy data with glaciological modeling experiments to examine past GIS changes and predict future GIS retreat. Results from this project will enable a more accurate prediction of the NW Greenland cryospheric response to a future warmer world and provide information directly relevant to predictions of future sea-­level rise.

GRIT Traverse Route

Spatial Variability of Physical and Chemical Firn Properties, Northern Greenland

Funded by NSF ANS to Bob Hawley (Dartmouth); Collaborators: Zoe Courville (CRREL), Eric Lutz (Dartmouth)

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 rates on the ice sheet from the northwest coast to the ice divide.

Publications: Hawley et al., 2014; Wong et al., 2013

North Pacific Holocene Climate Variability and Forcing

Funded by NSF ANS (ARC-0612400) to Paul Mayewski (UMaine); Collaborators: Karl Kreutz (UMaine), David Fisher (GSC), Christian Zdanowicz (GSC)

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). 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.

Publications: Zdanowicz et al., 2014; Fisher et al., 2008; Fisher et al., 2004; Osterberg et al., under review;

Trends and Sources of Atmospheric Pollution

Funded by NSF ANS (ARC-0612400; ARC-0714004; ARC-1140098) and NSF GSS (BCS-123284); Collaborators: Paul Mayewski (UMaine), Karl Kreutz (UMaine), Susan Kaspari (CWU), Mukul Sharma (Dartmouth)

Pb pollution record from ice coresIce 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.

Currently, Sam Beal (Dartmouth PhD student) has been funded to analyze the Mt. Logan ice core for total mercury concentrations to better understand the natural cycling and human emissions of this element through the last 10,000 years. Furthermore, we are collaborating with Susan Kaspari (CWU) and her students to develop a record of North Pacific black carbon pollution from the Mt. Logan core.

I was also funded by a RAPID grant from NSF ANS to determine the magnitude of radioactive cesium fallout in Alaska and Greenland from the 2011 Fukushima Dai-Ichi nuclear power plant disaster. These samples show that models may have under-estimated the amount of fallout deposited in Alaska.

Publications: Gross et al., 2012; Kaspari et al., 2009; Osterberg et al., 2008; Norton et al., 2007;

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: Kehrl et al., 2014; Gorman et al., 2013; Campbell et al., 2013; Campbell et al., 2012a; Campbell et al., 2012b; Upton and Osterberg, 2007; Osterberg, 2006

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

Paleoclimate records have demonstrated conclusively that the climate system is capable of abrupt, 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 opportunity to understand the forcing mechanisms of these events from a more diverse range of paleoproxies. We have been investigating the signature and forcing mechanisms 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). seismic history of the region.

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 analysis 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: Koffman et al., 2014; Osterberg et al., 2006