Coring a Ponderosa pine with Mt. Rainier in the background, fieldwork 2011.

Coring a Ponderosa pine with Mt. Rainier in the background, fieldwork 2011.

I study our Earth’s climate – past and present!  I research past water & climate primarily through dendrochronology, or tree-ring science, and the C-TRĒS research group consequently overlaps with the related fields of ecology and hydrology.  Most of my work focuses on climate patterns in western North American, past hydroclimate extremes (droughts and floods), and the ocean–atmosphere systems (like El Niño) that drive climate variability over time.

For more information on recent projects, read about my NSF-funded projects below or take a look at our publications. Click HERE for a variety of research profiles and news-related links

Research projects funded by the National Science Foundation:

Multi-Century Perspectives on Current and Future Flow in the Lower Missouri River Basin.  Funded by NSF P2C2 Program, 2020-2023. Collaborators: Connie Woodhouse, Ed Cook, Matt Dannenberg, Greg Pederson, Greg McCabe, Justin Martin.

The Lower Missouri River Basin, which has had multiple floods and droughts over recent decades, is one of the few remaining major river systems in the U.S. lacking long-term records of streamflow, in large part due to the scarcity of reliable instrumental data for flow calibration. Our study will combine observed and modeled hydrology to develop needed calibration series and will incorporate complementary tree-ring reconstruction approaches to produce spatial, seasonal runoff records for key sub-basin gages. The methods developed through this project will be widely applicable to other, similar studies that are hindered by sparse or inadequate instrumental-period data. We’ll also be evaluating multi-century synoptic climate controls on Lower Missouri River flow within a broader North American context, analyzing the impact of warming temperatures on future flow, and engaging with resource managers with the aim of producing reconstructions and projection information that is useful for water resource management. Click HERE to go to the project website.

High Frequency Hydroclimate Extremes and Synoptic Climate Drivers in Western North America at the End of the Little Ice Age.  Funded by NSF P2C2 Program, 2018-2022. Collaborators: Cary Mock.

Understanding extreme climate events like floods and droughts, which have major impacts on society and ecosystems, has become particularly important in light of the likelihood of future changes in extremes in a warming climate. Paleoclimate data have played a critical role in placing recent hydroclimate extremes within a longer-term context, but biases in paleoclimate proxies remain a major challenge for the reconstruction and interpretation of past climate extremes. This is particularly applicable to the North American West Coast, where a limited number of seasonal extreme precipitation events account for a large proportion of annual precipitation totals. This research will integrate historical climatology and dendroclimatology to address pre-instrumental capture of extremes through a focus on the 1800s, a time period including a range of climate extremes that are not represented in the instrumental record. Through this project, we plan to: (1) extract 19th century historical data from archives and repositories to derive sub-seasonal precipitation and snow frequency reconstructions; (2) use tree-ring data to assess the ability of existing records to capture hydroclimatic extremes (with a focus on atmospheric river events) and seasonally-specific precipitation on the West Coast; and (3) integrate historical and tree-ring data to create spatial climate surfaces for extreme events in the 1800s and use reanalysis data, gridded paleoclimate reconstruction data, and paleoclimate model output to assess synoptic climate drivers of those extremes.

Multi-Site Paleo-Reconstruction of Missouri River Streamflows from Tree Ring Data.   Funded by NSF P2C2 Program, 2014-2018. Collaborators: C. Woodhouse, E. Cook, G. Pederson, and many others.

The Missouri River Basin has experienced both floods and droughts that have interfered with the many services it provides, which include navigation, recreation, habitat, hydroelectric power, and agriculture. Despite the river’s importance, there was limited information on the climate controls on flood and drought in this basin, and there were no records on the range of long-term flow variability in the river system. Our detailed study of the links between climate and streamflow in the Missouri River Basin over the instrumental period provided a new baseline for studying climate-streamflow extremes and the effects of climate change in the region.  To research the pre-instrumental past, we used newly established and existing tree-ring chronologies to reconstruct a 1200-year flow history for streamflow gages important to river managers; this is the first long-term history of flow in the Missouri River.  We found that temperature has increasingly influenced streamflow variability and the intensity of drought events in the basin since the late 20th century. Click here to go to the project website. Data produced from this project are available HERE (NOAA) and HERE (USGS).

Detection of long-term variability in storm tracks using seasonally resolved tree-ring isotope records: Implications for hydroclimatic change in the U.S. Pacific Northwest. Funded by NSF P2C2 Program, 2013-2017. Collaborators: S. McAfee and A. Csank.

Our research team collected over 100 tree-ring cores and collected soil moisture samples twice a year from six sites around the Columbia River Basin for δ18O isotope analysis. Weekly precipitation samples were collected from 2013-2016 through a partnership with a citizen-science program and were continuously analyzed for isotopic composition. We used the stable isotope data in tree rings, soil moisture, and rain and snow to study how moisture delivery to western North America has changed over hundreds of years. We focused on the U.S. Pacific Northwest, with implications for water resources in the Columbia River Basin.  All data produced from these studies have been made publically available; click HERE for links.

Synoptic Dendroclimatology: Using Tree Rings to Reconstruct the Driving Forces of Hydroclimatic Variability in the Western USA. Funded by NSF P2C2 Program, 2011-2015.

Through this project, we reconstructed atmospheric controls on western North America hydroclimate variability using synoptic dendroclimatology techniques.  A major outcome of this project was the development of a tree-ring based climate field reconstruction of yearly cool-season atmospheric pressure (500 hPa geopotential height) on a 2° x 2° grid over western North America and the northeastern Pacific Ocean back to 1500 CE. A second major outcome of this project was the collection of over 500 tree-ring cores from eight sites in Washington, which were used to reconstruct storm tracks to 1693 CE. A third component of this project examined how the changing spatial footprint of ocean-atmosphere oscillations like El Niño and PDO might impact our interpretation of their impacts in teleconnected regions and our ability to reconstruct teleconnection indices using paleoclimate proxies.   Data produced from these studies have been made publically available; click HERE for links.