North Pacific Climate Change over the Holocene
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: Polashenski et al., 2018; Winski et al., 2018; Osterberg et al., 2017; 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
The South Pole Ice (SPICE) Core and Upstream Dynamics
We analyzed the 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 was essential for developing the ice core timescale that has been 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.
Impacts of Climate Change on the USA
We use station records and climate models to investigate the impacts of climate change on the USA. Our current research concerns the impact from the polar jet stream over North America. Trevor Partridge’s 2018 paper found seasonality in a mid-20th century cooling trend in the southeast USA (the “US Warming Hole”). We were able to link winter cooling there to an increase in jet stream waviness decades before 1990s-era potential changes in jet stream waviness have been observed elsewhere (e.g. Francis and Vavrus, 2012). Now, after hearing anecdotes that day-to-day temperature swings are getting worse throughout the country, we are investigating the concept of “weather whiplash” (large variations in interdaily weather conditions and temperature). Is this perceived trend even real? If so, what might be causing it? If not, what does that tell us about how we experience climate change?
Being based in New Hampshire, we have a particular interest in modern climate changes in the Northeastern USA. We have studied records of temperature and precipitation change here since 1900 to evaluate the signature and pace of climate change, and assess its causes. We 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. See the series of papers published by our former PhD student Huanping Huang for more.