Wooster Geologists

Advised by: Dr. Wiles

Abstract: Reconstructing and understanding historical lake levels provides information about how climate influences lake level fluctuations, which is important for managing Lake Michigan- Huron’s (MH) coasts. This study reconstructs historical MH lake levels using ten ring-width chronologies from Southeast Alaska, which are significantly correlated at the 0.01 confidence level with January – June average MH lake levels. Tree ring chronologies from Southeast Alaska can be used to create a model of MH because of atmospheric teleconnections, like the Pacific North American Pattern (PNA), which produce similar atmospheric pressure anomalies across both regions. The model explains 33.8% of the variance in MH lake levels (January – June), and the validity of the model was tested through a series of calibration and verification statistics, confirming a well-verified stable relationship through time.

Findings indicate that MH lake level fluctuations are primarily based on large-scale atmospheric climate patterns that may be altered by human activity, volcanic eruptions, or strong climate events. Reconstructed high lake levels are attributed to volcanic activity in the 1690s, 1673, 1755, and 1809 and a strong El Niño event from 1876 to 1878, whereas lows are attributed to droughts, corresponding with the conditions of the 1930s Dust Bowl. MH lake levels are negatively correlated with the Pacific North American Pattern (PNA), indicating higher lake levels during a negative PNA. Understanding why lake levels reached highs and lows in the past will give insight into lake level behavior in the present and into the future, helping manage MH’s coasts and protect shorelines.

Lynnsey explaining the results of her project at senior I.S. Symposium.

Reconstruction lake levels vs. actual lake levels (Jan – June). Drops in lake levels occur after the dredging of the Chicago Diversion (1886) and the dredging of the St. Clair River (1908 – 1925). However, the model also depicts drops at the same intervals, so these events may not have had an extraordinary impact on lake levels.

Reconstruction of January – June MH lake levels (1650 – 1990). Many of the early highs are linked to volcanic eruptions and later highs and lows are linked to regional or global climate events. Gray bars represent the 95% confidence interval derived from the root squared mean error (RSME).

Mary Palmieri’s senior IS was one of the first attempts at using tree-rings to reconstruct cloud cover. A double major in Earth Sciences and Statistical and Data Sciences, Mary was advised by Drs. Wiles and Pasteur.

Abstract: The climate of the Northeast United States has been changing rapidly since the 1970s, and cloud cover poses one of the biggest unknowns in climate modeling. Cloudiness has the potential to influence tree growth, and the temperate forests of the Northeast are poorly understood. In this study, nested principal component regression analysis was utilized to build a reconstruction of June through September (JJAS) cloud cover in the Northeast United States from 1801 to 2002. Ring width data from various oak species and latewood blue intensity data from eastern hemlock (Tsuga canadensis) were used to create a time series that explains at most 43.18% of the variance in average Northeast JJAS cloud cover. The reconstruction suggested that cloudiness in the 1800s and early 1900s was primarily forced by volcanoes and widespread deforestation. After the 1950s, cloud cover changes were dominated by rising sulfate aerosol and greenhouse gas emissions. Shifts in the 1920s and 1970s were likely intensified by coeval changes in the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation, respectively. High summer cloudiness is associated with less dense hemlock latewood and wider oak annual rings. However, precipitation has a more direct effect on tree growth than cloud cover. Hemlock trees are most impacted by decreased light availability and cloud-induced temperature changes, whereas oak trees are primarily limited by moisture. This study lays the groundwork for future paleoclimatic reconstructions of cloud cover using tree rings and provides a better understanding of Northeast temperate forest climate interactions, which will be integral given the uncertainty clouds pose in the wake of modern climate change.

Mary describing the results of her work during the senior IS Symposium.

Map showing the locations and correlations of the 30 chronologies used in the modeling. These all have significant correlations at the 95% confidence level with 1906 to 1973 average JJAS
cloud cover inside the region bound by the black rectangle.

Northeast JJAS cloud cover reconstruction in percentage from 1801 to 2002. Both the original reconstruction and a smoothed version are shown. The top ten highest and lowest cloud cover events are labeled with the respective years. The horizontal line indicates the mean.

JJAS Northeast cloud cover reconstruction, JJAS AMO, and annual global volcanic forcings from 1801 to 2002. Horizontal gray lines indicate the mean. The red boxes highlight time periods where volcanic eruptions may have influenced cloud cover, and the blue boxes show when the 35-year running correlation between the cloud cover reconstruction and the AMO was significant at a 95% confidence level.

It was a honor to welcome Dr. Nicolás Young (’05) back to the College to be our 44th Osgood Speaker. Dr. Young hails from the Lamont-Doherty Earth Observatory’s Cosmo Lab, where he is a Associate Research Scientist. Nicolás is a leader in developing the analytical side of cosmogenic surface exposure dating and is a gifted and creative field geologist.

His Osgood talk “Disappearance of North Atlantic ice sheets over the last 2.6 million years”  focused on his work with colleagues aimed at trying to figure out what ice sheets may have looked like during past warm intervals in Earth’s recent history, which is particularly important considering Earth’s current climate trajectory. This work is extremely challenging because evidence of small ice sheets has largely been destroyed by repeated episodes of subsequent ice advance. His team has been combining new sampling approaches in the field with evolving geochemical techniques to better constrain what ice sheets may have looked like during the past warm times. He outlined methods of sampling bedrock along ice sheet margins (Barnes Ice Cap) that has become ice free in the last few years, and drilling through existing ice to sample bedrock currently resting beneath extant ice sheets (Greenland). He deftly described how geochemical measurements from these unique samples help determine how often in the recent geologic past the Laurentide and Greenland ice sheets completely disappeared.  This work focused on recent results of a major project Greendrill as well as his ongoing projects on Baffin Island’s Barnes Ice Cap.

News to many in the audience is that the Laurentide Ice Sheet still exists as the remanent Barnes Ice Cap on Baffin Island in the Canadian Arctic. It was the Barnes Ice Cap and the fascinating story of its recent (the last few millennia) history that blew many of us away. Nicolás presented these recent results to our Geoclub. Note the trimline around the extent of the ice cap pictured above in this Sentinel image.

Nicolás speaking to Geoclub on his recent discoveries at the Barnes Ice Cap.

I can’t give the story away as the article is in review (I will post again when it comes out). The gray trimline area seen in the figure above marks a “recent” advance to this 1960 CE position, after which retreat has dominated. Nicolás described the trimline as a knife-edge and that only through careful dating using cosmogenic isotopes could one determine when this “recent” advance of ice began. The significance of this recent advance of the remanent of the Laurentide Icesheet is remarkable and transforms our thinking of Earth’s recent climate history.

We greatly thank the Osgood family for endowing the funds to bring innovative science to our Wooster community each year.

Dr. Mark Abbott and his graduate students Cole and Adeel visited the Wooster Tree Ring Lab with portions of white oak beams from a historic cabin in Pittsburgh. The mission was to tree ring date the outer ring of the samples to determine which calendar year the timber was cut for the structure. Here the Pitt team in the sample prep. lab with the two samples where they polished them for analysis.

Nick Wiesenberg oversaw the dating, which started with a tour in the west wing of the Wooster Tree Ring Lab.

Adeel measured one of the samples – understandably he is amazed with the anatomy of the white oak rings.

Cole measured the other sample measuring ring widths from the screen using CooRecorder. The Pitt group are exports in lake core analysis and both Adeel and Cole are analyzing lake varves, they are also thinking about using this measuring setup for varve analyses (see below).

Nick takes the controls and analyzes the measurement data against our tree-ring database and reveals the date of cutting for the cabin.

The crossdating with our master series shows that the outer ring of the samples were both 1834, at least for the two samples both were cut in the same year after the 1834 growing season so the cabin was likely built shortly after this. The 1698/99 rings are strong markers.

The varves that the Pitt team are analyzing are shown above – they may be annual like tree-rings and their research will extract paleoenvironmental data from these. This core was taken by the group a few weeks before their visit to Wooster in Northern Minnesota where it was tens of degrees below zero. See below.

The coring operation in Minnesota – ~12 inches of ice and 60 feet of water and then a few tens of meters of mud is the sequence through this ice hole.

Dr. Lyon’s class along with her TAs and in collaboration with the Wooster Art Museum’s director Dr. Marianne Wardle, significantly upgraded many of the fossil and mineral displays in Scovel Hall this past fall.

The classes hard work was revealed in an “opening” on the last day of Geoclub with students presenting their work to the Wooster Earth Scientists.

One of the formerly empty cases in the North entrance of Scovel Hall is now populated with new displays that are Ohio-centric.

Each of the geologic time periods is represented, and in this case, fossils from Ohio are keyed to each period are explained.

A detail of one of the cases and Ohio’s fossils.

Another new addition to Scovel Hall is a case on the first floor with examples of various modes of preservation and remarkable aesthetics in the setup with cards that offer explanations for each specimen.

Modes of preservation was a topic in much of the interpretive materials in the first floor case.

A detail from one of the shelves of the first – floor case.

Departmental technician, Nick Wiesenberg, painted over the not-so-nice pink color that was pervasive in our building, making this almost-three-story-wall shades of blue to provide an oceanic backdrop. Its great to see these displays each day and to see an increase in student, faculty, staff and visitors reading and interacting with the materials. Thank you Dr. Lyon, students and TAs from Paleoecology as well as the Wooster Art Museum and Nick for his support of this project.

Imagine a world with larch trees in the uplands and dawn redwoods in the flats, and bald cypress trees in the wetlands. This existed in the Eocene (~40 million years ago) when the world was warmer, the treeline was at higher latitudes and altitudes, and carbon dioxide in the atmosphere was more than two times Earth’s preindustrial levels. In fact, in the high Arctic where no trees can survive today, deciduous conifers were as lush in terms of carbon sequestration and bioproductivity as today’s rain forests.  Now, imagine a world that is sliding back into the greenhouse after millions of years of relative icehouse conditions.

How can we better understand the role of deciduous conifers in the biosphere and their utility in a warmer world. One “natural” experiment is to use dendroclimatology to infer the response of deciduous conifers to a warmer and wetter world. Secrest Arboretum in Wooster, Ohio has two species of larch trees (Siberian and European) as well as bald cypress and dawn redwood trees. These species are all exotic to Ohio and have been growing in the arboretum in some cases for over 100 years. How do they grow in their new homes? This is the subject of a new paper from the Wooster Tree Ring Lab published in Plants People and Planet.Dawn Redwoods from the Arboretum

The Weather station active in the Arboretum since the late 1800s provided the monthly climate records.

Here is the upshot of the work: Rising temperatures and wetter conditions in the Midcontinent of North America are influencing climate responses in trees. Dendroclimatological analyses of the four exotic deciduous conifer species from Secrest Arboretum, Northeast Ohio help identify past, present, and future climate-tree interactions. Analyses suggest that two larch species have changed their response to climate, whereas dawn redwoods and bald cypress trees are well suited for the present and future climate. This study elucidates tree responses to climate gleaned from a largely untapped source of tree growth in arboreta that can be more broadly applied at other sites as well as facilitate forest management decisions.

This effort included professors, staff and students at The College of Wooster as well as our collaborator and geo-ecologist Dr. Ben Gaglioti from the University of Alaska – Fairbanks. We thank Jason Veil (the curator of Ohio State University’s Secrest Arboretum) and its staff and volunteers for managing this amazing facility and for allowing us to sample the trees. We also acknowledge support of the National Science Foundation, Division of Earth Sciences, Grant/Award Numbers: EAR 2039939, GP-2023154.