Dr. Pamela Grothe (Medley) is an Assistant Professor in the Department of Earth and Environmental Sciences at the University of Mary Washington. She completed a Ph.D. in Paleoclimatology at Georgia Institute of Technology. Her current research uses fossil oysters and corals to reconstruct climate change over the past hundreds to thousands of years in order to put present-day climate change into context. Her work led to the discovery that El Niño Southern Oscillation (ENSO) variability is stronger today than over the past 6000 years.
Areas of Expertise (8)
Climate Change Science
Earth and Atmospheric Science
Hartley Corporation Fellowship (professional)
Awarded by Sigma Delta Epsilon/Graduate Women in Science, 2014.
National Science Foundation Scholarship (professional)
Awarded to facilitate attendance at the Urbino Summer School in Paleoclimatology, 2014.
Presidential Fellowship (professional)
Awarded by Georgia Institute of Technology, 2012.
Silver Medal Award (professional)
Awarded by the Cooperative Institute for Research in Environmental Sciences (CIRES) for scientific or engineering achievement, 2009.
Victor Zullo Memoria Research Award (professional)
Awarded by the University of North Carolina Wilmington to support a student in the Department of Geology, 2007.
Sylvia and B.D. Schwartz Graduate Fellowship Award (professional)
Awarded by the University of North Carolina Wilmington, 2007.
Georgia Institute of Technology: Ph.D., Earth and Atmospheric Science 2017
University of Colorado at Boulder: M.S., Geological Sciences 2012
University of Mary Washington: B.S., Geology 2006
Graduated with Honors.
- American Geophysical Union: Member
- The Geological Society of America: Member
- Graduate Women in Science: Member
Media Appearances (6)
WHRV 89.5, WAMU-FM tv
It's a health issue as well and it's all correlated because part of the reason that there are more underlying health conditions in these more marginalized communities is a good bit due to the air pollution from the highway traffic that's going through those neighborhoods that increases the rates of asthma, which makes dealing with extreme heat much harder. Pamela Grothe is a professor of environmental science at the University of Mary Washington.
'24 Hours of Reality' digital conversation discusses COVID-19, climate change and voting
The Free Lance-Star print
'24 Hours of Reality' digital conversation discusses COVID-19, climate change and voting
Dr. Pamela Grothe on Climate Change During the Pandemic
Dr. Pamela Grothe on Climate Change During the Pandemic
LETTER: Smarter choices will lead to net-zero emissions
The Free Lance-Star online
As a professor for UMW’s COVID-19 in Context course, I spoke to students and community members on how the worldwide shutdown of economies has affected climate change.
Cost of Clean Energy Act overblown
The Free Lance-Star print
The Free Lance–Star’s recent editorial, [“Bad time for $50/month energy tax,” May 14] was just this paper’s latest in a series of shortsighted tirades against clean energy and efforts to address the climate crisis.
VA Scientist Finds Another Reason for Extreme Weather
WVTF Radio IQ online
By studying fossilized coral, Grothe determined that extreme El Ninos correspond closely with the time when people began burning coal and oil. “The industrial record really sticks out like a sore thumb," she says. "If you look at the last twenty years – at the intensity of these swings – they are stronger than any 20-year period from the pre-industrial record.”
EESC 111 - Our Dynamic Earth (4 Credits)
The modern view of the Earth as a dynamic, constantly-changing planet and the impact of geological processes on our lives. Discussions will include the origin of the solar system and Earth, how earthquakes and volcanoes result from heat-driven plate tectonic processes and our ongoing attempts to predict such hazardous events, and how Earth's rocks and minerals are ingrained in our everyday lives. Streams and groundwater processes, and cycles of mountain uplift and erosion that continuously alter the Earth’s surface, will also be examined. Laboratory.
EESC 355 - Icehouse-Greenhouse Earth (3 Credits)
Prerequisite: EESC 111 or EESC 112 or EESC 120 or EESC 121. This course examines the history of the Earth’s climate system in the context of the two primary modes: Icehouse and Greenhouse. Through critical evaluation of primary literature, written assignments and oral presentations, students will gain an appreciation of the magnitude of temporal and spatial climate reorganizations through time and develop an in-depth understanding of both long and short term cyclic changes that have contributed to the development of our modern climate system.
EESC 121 - Oceanography (4 Credits)
An introduction to the oceans. Physical and chemical processes affecting seawater; the geology of the seafloor; biological productivity in the oceans; and environmental challenges involving the oceans. Laboratory.
EESC 311 - Sedimentation and Stratigraphy (4 Credits)
Prerequisite: EESC 111; prerequisite or corequisite CHEM 111; recommended: EESC 301 This course provides an overview of the concepts associated with sedimentary rock formation, including theoretical sedimentology, process oriented facies analysis and applied stratigraphy in the context of cyclic sea level and climate change through time. Class work includes several field trips to collect samples for physical and chemical analysis. Laboratory.
EESC 360 - UMW in Bonaire - Coral, Climate, and Conservation (4 Credits)
The purpose of this course is to learn about the interrelationship between corals and anthropogenic stressors, with particular emphasis on climate change. Coral reefs serve a diverse ecosystem but are under major threat globally due to warming waters. Additional factors, such as pollution, over fishing, and coral disease cause stress on coral reefs on a more regional level, and when compounded with global warming and ocean acidification, have led to the decline in coral reefs around the world. Students learn about coral reefs, climate change, and regional stressors as well as discuss what can they do, as people and as a society, to improve the situation. Students travel to Bonaire to observe coral reef environments first-hand through SCUBA and to practice coral conservation techniques, such as coral gardening.
Estimated 2020 CO2 Emission Reductions in Virginia’s Transportation Sector from COVID-19Virginia Journal of Science
Eden E. Rakes, Pamela R. Grothe, Jeremy S. Hoffman
2021 The initial lockdown phase of the COVID-19 pandemic presented an unfortunate opportunity to observe how abrupt, large-scale changes in traffic volume can reduce greenhouse gas emissions. This study explores how carbon dioxide (CO2) emissions from Virginia’s transportation sector may have been affected by the changes in activity stemming from COVID-19 to inform more carbon-neutral policies as the state recovers from the economic downfall. Emission savings were calculated by multiplying the percent change from 2019 to 2020 in traffic volume from the Virginia Department of Transportation with the business-as-usual 2020 U.S. Environmental Protection Agency estimate of CO2 emissions for Virginia’s transportation sector. We estimate Virginia’s 2020 COVID-19 transportation CO2 emissions reduction is around 15.0% (14.2 to 15.7%), with reduced passenger vehicle traffic making up the bulk of the inferred reduction. This study highlights the utility of reimagining our current transportation sector as a way to implement sustainable, state-level carbon reduction policies, such as the Clean Car Standards.
Enhanced El Niño–Southern Oscillation Variability in Recent DecadesGeophysical Research Letters
Pamela R. Grothe, Kim M. Cobb, Giovanni Liguori, Emanuele Di Lorenzo, Antonietta Capotondi, Yanbin Lu ,Hai Cheng, R. Lawrence Edwards, John R. Southon, Guaciara M. Santos et al.
2019 The El Niño–Southern Oscillation (ENSO) represents the largest source of year-to-year global climate variability. While Earth system models suggest a range of possible shifts in ENSO properties under continued greenhouse gas forcing, many centuries of preindustrial climate data are required to detect a potential shift in the properties of recent ENSO extremes. Here we reconstruct the strength of ENSO variations over the last 7,000 years with a new ensemble of fossil coral oxygen isotope records from the Line Islands, located in the central equatorial Pacific. The corals document a significant decrease in ENSO variance of ~20% from 3,000 to 5,000 years ago, coinciding with changes in spring/fall precessional insolation. We find that ENSO variability over the last five decades is ~25% stronger than during the preindustrial. Our results provide empirical support for recent climate model projections showing an intensification of ENSO extremes under greenhouse forcing.
El Niño–Southern Oscillation complexityNature
Pamela R. Grothe et al.
2018 El Niño events are characterized by surface warming of the tropical Pacific Ocean and weakening of equatorial trade winds that occur every few years. Such conditions are accompanied by changes in atmospheric and oceanic circulation, affecting global climate, marine and terrestrial ecosystems, fisheries and human activities. The alternation of warm El Niño and cold La Niña conditions, referred to as the El Niño–Southern Oscillation (ENSO), represents the strongest year-to-year fluctuation of the global climate system. Here we provide a synopsis of our current understanding of the spatio-temporal complexity of this important climate mode and its influence on the Earth system.
A comparison of U/Th and rapid‐screen 14C dates from Line Island fossil coralsGeochemistry, Geophysics, Geosystems
Pamela R. Grothe, Kim M. Cobb. Shari L. Bush, Hai Cheng, Guaciara M. Santos, John R. Southon, R. Lawrence Edwards, Daniel M. Deocampo, Hussein R. Sayani
2016 Time‐consuming and expensive radiometric dating techniques limit the number of dates available to construct absolute chronologies for high‐resolution paleoclimate reconstructions. A recently developed rapid‐screen 14C dating technique reduces sample preparation time and per sample costs by 90%, but its accuracy has not yet been tested on shallow‐water corals. In this study, we test the rapid‐screen 14C dating technique on shallow‐water corals by comparing 44 rapid‐screen 14C dates to both high‐precision 14C dates and U/Th dates from mid‐ to late‐Holocene fossil corals collected from the central tropical Pacific (2–4°N, 157–160°W). Our results show that 42 rapid‐screen 14C and U/Th dates agree within uncertainties, confirming closed‐system behavior and ensuring chronological accuracy. However, two samples that grew ∼6500 years ago have calibrated 14C ages ∼1000 years younger than the corresponding U/Th ages, consistent with diagenetic alteration as indicated by the presence of 15–23% calcite. Mass balance calculations confirm that the observed dating discrepancies are consistent with 14C addition and U removal, both of which occur during diagenetic calcite recrystallization.
Climatic and biotic thresholds of coral-reef shutdownNature Climate Change
Lauren T. Toth, Richard B. Aronson, Kim M. Cobb, Hai Cheng, R. Lawrence Edwards, Pamela R. Grothe and Hussein R. Sayani
2015 Climate change is now the leading cause of coral-reef degradation and is altering the adaptive landscape of coral populations. Increasing sea temperatures and declining carbonate saturation states are inhibiting short-term rates of coral calcification, carbonate precipitation and submarine cementation. A critical challenge to coral-reef conservation is understanding the mechanisms by which environmental perturbations scale up to influence long-term rates of reef-framework construction and ecosystem function. Here we reconstruct climatic and oceanographic variability using corals sampled from a 6,750-year core from Pacific Panamá. Simultaneous reconstructions of coral palaeophysiology and reef accretion allowed us to identify the climatic and biotic thresholds associated with a 2,500-year hiatus in vertical accretion beginning ∼4,100 years ago. Stronger upwelling, cooler sea temperatures and greater precipitation—indicators of La Niña-like conditions—were closely associated with abrupt reef shutdown.
Challenges in Building Coastal Digital Elevation ModelsJournal of Coastal Research
Barry W. Eakins and Pamela R. Grothe
2014 Digital elevation models (DEMs) support a wide variety of uses, including modeling of surface processes, habitat mapping and conservation planning, coastal change and terrain analysis, and Earth visualization and exploration. These models may, however, contain significant deviations from the surface they are intended to represent, which could reduce their usefulness. Additional complexities arise when integrating bathymetric and topographic data to create coastal DEMs. We identify common challenges in building square-cell, coastal DEMs and present some solutions. These challenges are grouped into six general categories: (1) source data, (2) data processing, (3) model development, (4) model assessment, (5) morphologic change, and (6) model uncertainty. Some DEM best practices to help improve DEM accuracy and utility include: visual inspection of source data in a geographic information system (GIS) environment; establishing common horizontal and vertical datums; using data buffers and bathymetric presurfaces; assessing DEM accuracy; accounting for morphologic change; and quantifying DEM uncertainty at the cell level.
Propagation history of the Osaka-wan blind thrust, Japan, from trishear modelingJournal of Structural Geology
Pamela R.Grothe, Nestor Cardozo, Karl Mueller, Tatsuya Ishiyama
2013 Mapping the nucleation and 3D fault tip growth of the active Osaka-wan blind thrust provides an opportunity to asses how reactivated thrusts build slip from preexisting faults and the threat they pose as sources of large earthquakes. Analysis of folded growth strata, based on 2D trishear inverse modeling allows a range of best-fit models of the evolution of slip and propagation of the fault to be defined. The depth of the fault tip at 1200 ka varies between ∼1.5–4.5 km, suggesting the fault grew upward from high in the crust, and that it is reactivated. From its onset at ∼1500 ka, the fault grew rapidly along strike in ∼300 ky, and upwards with a P/S ratio of 2.5–3.0, but variable fault slip in space and time. Shallower depths of the fault tip at initiation and thinner basin fill correlates with slower propagation with time, contradicting models that argue for sediments as inhibitors of fault growth. Results also suggest the displacement profile of the currently active thrust is offset from its predecessor, assuming shallower depths to the original fault correlate with greater displacement in its prior history. These results suggest reactivated faults may accrue slip differently than newly developed ones, based on the history of upward fault propagation.
Glacial‐interglacial size variability in the diatom Fragilariopsis kerguelensis: Possible iron/dust controls?Paleoceanography and Paleoclimatology
G. Cortese, R. Gersonde, K. Maschner, P. Medley
2012 The valve area of Fragilariopsis kerguelensis, the most abundant diatom species in the Southern Ocean, strongly changes in size in response to varying conditions in the surface ocean. We examined the link, both in two iron fertilization experiments and in sediment samples covering several glacial Terminations, between size variability in this species and environmental conditions across the Antarctic Polar Front, including sea ice extent, sea surface temperature, and the input of eolian dust. The iron fertilization experiments show valve area to be positively correlated with iron concentrations in ambient waters, which suggests the possibility of a causal relation between valve size of Fragilariopsis kerguelensis and ambient surface water iron concentration. Larger valves are usually found during glacial times and thus seem to be related to lower sea surface temperature and wider sea ice coverage. Moreover, our results indicate that there usually is a strong correlation between larger valve size and increased input of eolian dust to the Southern Ocean.
Paleosalinity history of middle Holocene lagoonal and lacustrine deposits in the Enriquillo Valley, Dominican Republic based on pore morphometrics and isotope geochemistry of ostracodaMicropaleontology
Pamela Medley, Neil E. Tibert, William P. Patterson, H. Allen Curran, Lisa Greer, Jean-Paul Colin
2007 The southwestern region of the Dominican Republic (Enriquillo Valley) contains exceptionally well-preserved, relict marine and saline lake deposits of mid-Holocne age. Abundant euryhaline ostracodes found in this deposit include Cyprideis salebrosa, C. mexicana, C. similis, and C. edentata. Morphometric and geochemical analyses performed on Cyprideis spp. provide high δ18O and δ13C values that are coincident with relative abundances of irregularly shaped pores that permeate the ostracode carapace. We recognize three stratigraphic intervals with distinct ostracode pore shape and stable isotope trends: (I) a 4.5–5.0m interval that contains ostracodes with highly irregular shaped pores (multiradiate) and high amplitude variability in δ18O and δ13C values; (II) a 5.0–5.6m interval comprised of ostracodes with circular pores and an overall trend towards low δ18O and δ13C values; and (III) a 5.6–6.5m interval containing ostracodes with an upward increasing abundance of circular pore shapes coincident with decreasing δ18O and δ13C values.