Prof. Natalie Burls of AOES organized a one-day fellowship workshop in August to help advanced undergraduate, and junior graduate students, learn how to submit successful fellowship proposals. Dr. Kathryn Ágoston, the Director of Graduate Fellowships, gave an introductory presentation and materials on the fellowship opportunities available within the field of Atmospheric Oceanic and Earth Sciences, as well as the support offered by her office at Mason. The students were then asked to identify a fellowship opportunity they qualify for and present a few slides to the group outlining the application process. The students spend the remainder of the day drafting an application timeline. The workshop was attended by more than 10 students in the atmospheric sciences and climate dynamics programs and will be held annually here after.
V. Krishnamurthy, a research scientist at George Mason University’s Center for Ocean-Land-Atmosphere Studies (COLA) is among this year’s honorees for the American Geophysical Union (AGU), the world’s largest Earth and space science society. Dr. Krishnamurthy will be delivering the Ed Lorenz Lecture at the AGU Fall Meeting this year. The lecture is named for MIT meteorologist Ed Lorenz, who discovered the “butterfly effect” in weather.
This is one of AGU’s top honors, which is bestowed by the AGU Nonlinear Geophysics section. Coincidentally, Dr. Krishnamurthy was one of Prof. Lorenz’ doctoral students, and he is a recognized expert on nonlinear dynamics, general predictability theory and the predictability of the south Asian monsoon.
Bohar Singh defended his dissertation in Fall 2017 (advisor: Jim Kinter) on “Seasonality of the Tropical Intraseasonal Oscillations (TISOs): Sensitivity to Mean Background State”. Singh came to the George Mason from the Indian Institute of Science in Bangalore, India.
TISO refers to variations in atmospheric convection (hence rainfall and other features) that occur over about 1-3 months. One example of TISO is the Madden-Julian Oscillation (MJO), a band of enhanced convection that drifts eastward along the equator. Another example is Monsoon Intra-Seasonal Oscillation (MISO), which is an increase or decrease in convection that propagates northward over India during the rainy summer monsoon. TISOs are not as well understood as mid-latitude weather, which causes variations over a few days, and El Nino-Southern Oscillation, which causes year-to-year variation.
Singh found that the co-occurrence of warm climatological SST and mean westerly wind plays an important role in setting the location and propagation direction of TISO. Sensitivity experiments with an atmospheric General Circulation Model indicate that the regionality and seasonality of TISO are closely coupled to local sea surface temperature (SST) and the low-level circulation. The SST in the tropics must reach a required threshold for convection to occur, while the low-level circulation controls the direction of propagation by controlling the location of moisture convergence.
Dr. Singh is now a postdoctoral fellow at Colorado State University.
Guangyang Fang, working with Bohua Huang, defended his dissertation in Spring 2018. His research concerned “Seasonal Predictability of Tropical Atlantic Variability”.
Tropical Atlantic Variability (TAV) refers to year-to-year differences in sea surface temperature (SST) and related properties such as rainfall. So far, attempts to predict TAV months or more in advance
have not been very successful. This may be because TAV, unlike some other climate variability such as El Nino, is simply not predictable. On the other hand, climate models used to predict TAV have known flaws
which may be limiting predictability. If the latter is true, it is possible that improving the models will some day allow for better predictions.
Fang tested this idea with “perfect model” experiments, in which a climate state of the model itself is treated as “reality”. The model is then rerun starting at the climate state a few months earlier, but
with some random differences from the first run that represent small errors that are always present in measurements used to initialize the models. Since the same model, flaws and all, is used to create the “real” behavior and the “predicted” behavior, the flaws should not ruin the predictions. However, if the system is not predictable, then the model predictions will diverge from the original run just because
of the slightly different initial conditions.
Much of TAV is centered on either the northern hemisphere or the southern hemisphere of the tropical Atlantic. The experiment showed some prediction skill up to 9 months in advance for the northern mode and only 4 months for the southern mode. Fang’s diagnosis of the detailed behavior of the system showed that the northern mode was predictable because El Nino (which occurs primarily in the Pacific) influences the Atlantic, and the model shows skill in predicting El Nino. Predictability of the southern mode comes from the atmosphere-ocean interaction within the Atlantic region, and is not as robust as El Nino predictability.
Work by George Mason University post-doc Mingsong Li (now at Penn State University), his advisor AOES faculty member Linda Hinnov, and international collaborators, has been published in Nature Communications (Li et al, 2018) and received notice in AAAS Eureka Alert, ScienceDaily and elsewhere.
Today there is great concern that global warming will melt Greenland and Antarctic icecaps and the resulting meltwater will raise sea level, inundating coastal cities. Geological evidence shows that over the past million years, sea level rose and fell several times by over 100 m due to changes between ice ages and warmer climates such as we have had for the last 10,000 years.
Back in the Triassic Period (250 – 200 million years ago), sea level also oscillated by about 100 m at million-year timescales. At that time, however, the Earth was much warmer than today and there were no ice caps to affect sea level. What was responsible for the Triassic sea level changes if it wasn’t the ice?
Groundwater is another reservoir which can potentially hold a large volume. By analyzing sedimentary records, Li, Hinnov, and collaborators were able to find evidence that sea level and groundwater formed a kind of seesaw, in which rises in sea level occurred during reductions in groundwater and sea level falls occurred when groundwater was expanding. They argue that in considering how sea level will behave in the future, groundwater may play a larger role than previously thought.
AOES faculty member Cristiana Stan and David Straus are lead authors on an article featured on the cover of Reviews of Geophysics, a publication of the American Geophysical Union (AGU). Their article, “Review of Tropical-Extratropical Teleconnections on Intraseasonal Time Scales” concerns an area of climate research that is of great interest to AOES scientists. These interactions provide a potential tool for helping predict average weather behavior in mid-latitude regions (such as the United States) based on skill in predicting tropical weather variations such as El Nino.
A belated congratulations is due AOES faculty member Julia Nord who was one of only 8 faculty members to earn the George Mason University 2017 University Teaching Excellence Award. Dr. Nord is a geologist and former AOES undergraduate coordinator with a keen interest in pedagogy. The award recognizes her work in Formative Evaluation for Learning Retention, which are alternatives to high-stakes testing which better support learning retention.
The “Editors’ Vox” feature of Eos, the American Geophysical Union’s magazine, highlights an article by AOES professors Cristiana Stan and David Straus and their collaborators. The paper is Review of Tropical-Extratropical Teleconnections on Intraseasonal Time Scales (2017, Rev. Gepohys.). The Editors’ Vox piece has an interview with Dr. Stan about teleconnections – influences on weather and climate from distant parts of the climate system. COLA and AOES have long played an important role in the study of such teleconnections.
Whereas the earth sciences are fundamental to society; and
Whereas the earth sciences are integral to finding, developing, and conserving mineral, energy, and water resources needed for society; and
Whereas the earth sciences promote public safety by preparing for and mitigating natural hazards such as floods, landslides, earthquakes, volcanic eruptions, sinkholes, and coastal erosion; and
Whereas the earth sciences are crucial to environmental and ecological issues ranging from climate change and water and air quality to waste disposal; and
Whereas geological factors of resources, hazards, and environment are vital to land management and land use decisions at local, state, regional, national, and international levels; and
Whereas the earth sciences contribute critical information that enhances our understanding of Nature,
Therefore, be it resolved that the second full week of October henceforth be designated as Earth Science Week.
AOES adjunct professor and NSF Program Manager Dave Verardo was instrumental in creating Earth Science Week.
Water sinking into the deep subpolar North Atlantic Ocean from near its surface has an important influence on the chemistry of the ocean and atmosphere and the Earth’s climate. A famous question in physical oceanography asks why there is no such deep sinking in the North Pacific. Previous research has questioned whether Pacific sinking is even possible. AOES Assistant Professor Natalie Burls is lead author of a paper in Science Advances which argues that the ocean did indeed have such sinking during the Pliocene Epoch over 2 million years ago. The results have implications for future climate, since the warm Pliocene climate of yesterday may be an analogue to the warm climate of tomorrow caused by greenhouse as emissions.
Burls, Fedorov, Sigman, Jaccard, Tiedemann, and Haug, 2017: The warm, ~400ppm CO2 world of the Pliocene supported a northern-sourced meridional overturning cell in the Pacific Ocean.N
From the study press release
The modern ocean is characterized by a strong AMOC, which is of critical importance for nutrient cycles, and the air-sea exchange of carbon dioxide (CO2). The modern Pacific lacks such an overturning cell due to the presence of a layer of very fresh surface water (which oceanographers refer to as a halocline) preventing deep water formation, a crucial asymmetry between the two oceans that affects a broad range of climatic variables from the mean temperature of the North Atlantic to the position of the Intertropical Convergence Zone in the atmosphere. Why this asymmetry exists, and whether there were times in the past with different configurations of ocean deep cells, are fundamental questions in climate science.
Our fully coupled climate model simulations demonstrate that the large-scale sea-surface temperature patterns of the warm Pliocene, particularly the weak zonal and meridional sea surface temperature gradients, are capable of maintaining changes in the atmosphere’s hydrological cycle that act to increase the salinity of the subarctic North Pacific leading to deep water formation and an deep meridional overturning cell. On the data side, enhanced sedimentary calcium carbonate and biogenic opal accumulation provide direct evidence of deep water formation in a location that is remarkably consistent with the region in which our simulation predicts deep water formation. Taken together these results make a convincing argument that Pliocene conditions supported a strong Pacific meridional overturning cell (PMOC), comparable in strength to that existing today in the Atlantic.
The establishment of the PMOC is not a minor change in ocean circulation – in fact it is a major reorganization of ocean circulation with fundamental consequences for climate. The Pacific is by far the largest ocean basin and the presence of the deep meridional overturning in this basin would have had impacts, for example, on carbon and nutrient cycling globally with potentially important implications for the evolution of climate.
These findings might also provide some insight into the long-term (order thousands of years) trajectory of circulation changes in the Pacific under future global warming. While the oceans are expected to warm more at the surface than at depth initially, which will act to inhibit deep water formation in the Pacific, as the deep ocean slowly warms and if the waters of the subarctic Pacific become saline enough this may result in North Pacific deep water formation.
AOES Climate Dynamics has a strong presence at the NMME/SubX Meeting this fall at the NOAA Center for Weather and Climate Prediction (NCWCP). NMME is North American Multi-Model Ensemble, a national effort to improve seasonal climate forecasts by using climate models run by a number of institutions. SubX is the Subseasonal Experiment, concentrating on predicting climate change on scales shorter than a season.
AOES Assistant Professor (and Climate Dynamics Doctoral Program alumn) Kathy Pegion is one of the four organizers of the meeting, along with former AOES faculty member Ben Kirtman. Current students Teresa Cicerone and Bohar Singh and Professor Tim DelSole are participating, as are Climate Dynamics Program alumni Emerson LaJoie, Nala Barapusetty, Lakshmi Krishnamurthy, Rob Burgmann, Kristi Arsenault and Deepthi Achuthavarier.