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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 research projects in Greenland, Antarctica, the Northeastern US, and the North Pacific region, including Alaska and the Yukon Territory.

North Pacific Climate Change over the Holocene

Funded by NSF P2C2 (AGS-1204035; ARC-0714004) with collaborators: Cameron Wake (UNH), Karl Kreutz (UMaine) and Sean Birkel (UMaine); Also NSF ANS (ARC-0612400) to Paul Mayewski (UMaine) with Collaborators: Karl Kreutz (UMaine), David Fisher (GSC), Christian Zdanowicz (Uppsala, formally GSC)

The main goal of these collaborative Dartmouth-UMaine-UNH-GSC projects is to reconstruct the history of atmospheric circulation, temperature and precipitation in Alaska and the North Pacific region during the Holocene, and evaluate their forcing mechanisms, using an array of ice core records. 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 have been sampled with our continuous ice core melter, and analyzed for chemical concentrations and stable water isotopes to reconstruct past temperature, snow accumulation and storminess. These new records are being combined with an existing array of ice cores collected from the Wrangell, Saint Elias (Eclipse and Mt. Logan cores), and Brooks Range (McCall Glacier). Much of this research focuses on the changing strength of the Aleutian Low, which dominates wintertime climate in the North Pacific (see figure) and responds to tropical Pacific conditions (El Nino/La Nina). The project focuses on climate patterns during the Medieval Climate Anomaly (~800 to 1,200 years ago), the Little Ice Age (~200 to 600 years ago), and the modern industrial warming (last ~150 years). Check out the story and pictures of our 2013 drilling season on Mt. Hunter.

Publications (ARC-0714004): Osterberg et al., 2014; Zdanowicz et al., 2014; Campbell et al., 2013; Campbell et al., 2012a; Winski et al., 2012; Campbell et al., 2012b; Kelsey et al., 2010, Fisher et al., 2008; Fisher et al., 2004

Surface Mass Balance of the Greenland Ice Sheet

Funded by NSF ANS (ARC-1417678) with collaborators: Bob Hawley (Dartmouth); H.P. Marshall (Boise State), and Sean Birkel (UMain); and by NSF ANS (ARC-0909265) to Bob Hawley (Dartmouth) with collaborators: Zoe Courville (CRREL)

Greentracs_projectThis research aims to quantify changes in snowfall, temperature, snow density, surface melt, and snow reflectivity (albedo) across the Greenland Ice Sheet, to better understand how modern climate change is affecting Greenland mass balance (how fast is it melting?) and global sea-level rise. These projects provide valuable field data needed to validate climate models used to predict future melting of the ice sheet with continued warming. Our latest project is called "GreenTrACS" (Greenland Traverse for Accumulation and Climate Studies), and includes 1000+ km snowmobile traverses across western Greenland in 2016 and again in 2017 (see figure). Along the traverses we are collecting snow/ice radar data showing annual snowfall layers, high-precision surface elevation data to track the lowering of the ice sheet, snow reflectivity data to see how pollution and warming are darkening the ice sheet surface, and a series of 16 ice cores to track snowfall and snow melting over the past 40-50 years. Follow our blog, and check out the youtube video about this project.

Publications: Lewis et al., 2017; Osterberg et al., 2015; Hawley et al., 2014; Wong et al., 2013

The South Pole Ice (SPICE) Core and Upstream Dynamics

Funded by NSF OPP (OPP-1443336) with collaborators: Karl Kreutz (UMaine) and Jihong Cole-Dai (SDSU); and NSF OPP (OPP-1443341) with collaborators: Michelle Koutnik (UW), Howard Conway (UW), Ed Waddington (UW), Mary Albert (Dartmouth) and Bob Hawley (Dartmouth)

SPICEcoreWe are analyzing the new SPICEcore at high resolution for major ion and trace element chemistry to explore the signature and causes of natural climate change in the region surrounding Antarctica over the last 40,000 years. This is a period when the Earth transitioned from an ice age into the modern warm period. We are investigating how the wind belts that surround Antarctica changed in their strength and position through time, and documenting explosive volcanic eruptions and CO2 cycling in the Southern Ocean as potential climate forcing mechanisms over this interval. Understanding how and why the climate varied naturally in the past is critical for improving our understanding of modern climate change and projections of future climate under higher levels of atmospheric CO2. Our data are also be essential for developing the ice core timescale that will be used by all SPICEcore researchers. We are also investigating the ice upstream of the SPICEcore drill site to assess ice flow conditions, spatial patterns in snow accumulation, and firn compaction, all critical to the proper interpretation of the ice core.

Long-Term Trends and Sources of Air 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 recent falling pollution trends in the North Atlantic region.

Sam Beal's 2015 paper on changes in atmospheric mercury concentrations in the Mt. Logan ice mercury_pollutioncore allows us to better understand the natural cycling and human emissions of this element over the last 600 years (see figure to left modified from Beal et al., 2015).

Publications: Beal et al., 2015; Gross et al., 2012; Kaspari et al., 2009; Osterberg et al., 2008; Norton et al., 2007;



Northeast USA Climate Change and Impacts

Funded by the Neukom Institute of Dartmouth, with collaborators: Jon Winter (Dartmouth), Dorothy Wallace (Dartmouth), Matt Ayres (Dartmouth), and Jonathan Chipman (Dartmouth)

We are studying the record of temperature and precipitation change in the Northeastern USA since 1900 to evaluate the signature and pace of climate change, and assess its causes. Our current research is focused on the increase in extreme storms (determined by precipitation) in the Northeast over recent decades, and understanding its spatial variability (more along the coast or inland?), seasonality (more during winter or summer?), and underlying causes. We are also developing a next-generation model to study the effects of climate change, land-use patterns, and host dynamics on the spread of Lyme Disease. Our aim is to understand the relative importance of these factors in the rapid northward spread of the disease over recent years (see figure).

Response of the NW Greenland Ice Sheet 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 researchers 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.

Publications: Osterberg et al., 2015; Wong et al., 2015; Lasher et al., under revision.

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

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