Dr. Pamela Grothe (Medley) is an Assistant Professor in the Department of Earth and Environmental Sciences as the University of Mary Washington. She recently completed a Ph.D. in the Paleoclimatology Lab at the Earth and Atmospheric Sciences department at Georgia Institute of Technology. Her current research involves a study of the central Pacific climate and El Niño Southern Oscillation (ENSO) variability over the past 6000 years through the analysis of coral fossil records.
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)
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.”
New and Strange Climate Pattern Includes More Violent El Nino Swings
SciTechDaily; The Tribune; Space Daily; Daily Excelsior; Forbes online
“When I present it to people, I always get asked, ‘Where’s the temperature measurement?’ I tell them it’s there, but you can’t see it because the corals’ records of sea surface temperatures are that good,” said Grothe, a former graduate research assistant in Cobb’s lab and now an associate professor at the University of Mary Washington.
New York City will be under water in 100 years, experts issue stark warning as sea level rise speeds up
Dr. Pamela Grothe from the University of Mary Washington also told MEA WorldWide (MEAWW): "This new estimate is astonishing, which is about twice as high as what we previously thought. It would displace millions of more people living in low-lying coastal regions."
Politician Says Melting Sea Ice is a Good Thing, Climate Change Experts Disagree
Science Times online
Assistant professor of Earth and Environmental Sciences from the University of Mary Washington, Dr. Pamela Grothe said that Polar regions are important for regulating global temperatures. "Sea ice is highly reflective and when it melts, it exposes more ocean surface to absorb the sun's energy, causing even more warming. This will then accelerate even more sea ice loss."
Melting sea ice in the Arctic and Antarctic may be an economic boon, but it spells doom for sea life
Assistant professor of Earth and Environmental Sciences from the University of Mary Washington, Dr. Pamela Grothe, told MEA WorldWide (MEAWW) that Polar regions are important for regulating global temperatures. "Sea ice is highly reflective and when it melts, it exposes more ocean surface to absorb the sun’s energy, causing even more warming. This will then accelerate even more sea ice loss."
The 'great dying': rapid warming caused largest extinction event ever, report says
The Guardian.com online
The research group “provide convincing evidence that warmer temperatures and associated lower oxygen levels in the ocean are sufficient to explain the observed extinctions we see in the fossil record”, said Pamela Grothe, a paleoclimate scientist at the University of Mary Washington. “The past holds the key to the future,” she added. “Our current rates of carbon dioxide emissions is instantaneous geologically speaking and we are already seeing warming ocean temperatures and lower oxygen in many regions, currently affecting marine ecosystems. “If we continue in the trajectory we are on with current emission rates, this study highlights the potential that we may see similar rates of extinction in marine species as in the end of the Permian.”
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
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. Under the assumption that aragonite‐to‐calcite replacement is linear through time, we estimate the samples' true ages using the measured 14C and U/Th dates and percent calcite values. Results illustrate that the rapid‐screen 14C dates of Holocene‐aged fossil corals are accurate for samples with less than 2% calcite. Application of this rapid‐screen 14C method to the fossil coral rubble fields from Kiritimati Island reveal significant chronological clustering of fossil coral across the landscape, with older ages farther from the water's edge.
Lauren T. Toth, Richard B. Aronson, Kim M. Cobb, Hai Cheng, R. Lawrence Edwards, Pamela R. Grothe and Hussein R. Sayani
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. The physiological condition of the corals deteriorated at the onset of the hiatus, corroborating theoretical predictions that the tipping points of radical ecosystem transitions should be manifested sublethally in the biotic constituents. Future climate change could cause similar threshold behaviours, leading to another shutdown in reef development in the tropical eastern Pacific.
Barry W. Eakins and Pamela R. Grothe
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.
Pamela R.Grothe, Nestor Cardozo, Karl Mueller, Tatsuya Ishiyama
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.
G. Cortese, R. Gersonde, K. Maschner, P. Medley
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. However, this correlation, obvious for the fertilization experiments and for glacial Terminations I, II, III, and V, does not seem to be valid for Termination VI, where size appears to be inversely correlated to dust input.
Pamela Medley, Neil E. Tibert, William P. Patterson, H. Allen Curran, Lisa Greer, Jean-Paul Colin
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. When the Enriquillo lagoon was first separated from the Caribbean Sea approximately 4.3 ka, an arid and evaporative climate led to hypersaline water in a restricted lagoon environment. By the middle to late-Holocene, increased precipitation in the valley resulted in a coastal lake system that became progressively oligohaline. Moderate to small amplitude variability in the salinity proxy data (δ18O) suggest short-term oscillations in the precipitation-evaporation budgets at that time. At least two marine incursions likely contributed to the observed variability in ostracode δ18O and δ13C values. Evidence for abrupt changes in base level indicate that climatic factors or also tectonic activity may have contributed to the observed paleoenvironmental trends recorded in these deposits.