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.
David Straus, an AOES professor and COLA scientist, has been asked by the editors of Eos to contribute an article explaining “Concepts for Dealing with the Complexity of Weather and Climate”. Eos, named after the Greek goddess of the dawn, is the weekly magazine of the American Geophysical Union (AGU). His description accompanies a more detailed review article Dr. Straus co-authored in AGU’s Reviews of Geophysics.
From the article conclusion:
The ability of atmosphere and coupled atmosphere-ocean models to capture the observed preferred and persistent states (regimes) in the winds and temperature is an important area of research. In terms of week-to-week weather forecasting, the question is how well the models can predict the shifts between regimes, starting from the known initial state. The answer to this depends on two factors: one is the realism of the regimes simulated by the model in long simulations without any information from observations, and the second is how intrinsically predictable the regimes actually are.
Busy summer for AOES Professor & COLA scientist Paul Dirmeyer. In addition to his recent appointment to the GEWEX Scientific Steering Group, he has also been elected a Fellow of the American Geophysical Union (AGU). AGU is “dedicated to the furtherance of the Earth and space sciences” and has 62,000 members. Only one in a thousand members is elected to AGU Fellowships each year. Dr. Dirmeyer joins fellow AGU Fellow Jagadish Shukla as an AOES faculty member elected to the program, which “recognizes AGU members who have made exceptional contributions to Earth and space sciences” as based on their scientific breakthroughs, innovation, and/or scientific impact.
Dr. Dirmeyer teaches CLIM 714 Land-Atmosphere Interaction. He studies the impact of land surface variability on the predictability of climate, interactions between terrestrial and atmospheric branches of the hydrologic cycle, and the impacts of land use change on climate.
Inside Science, the popular news service covering scientific discovery, reported on a paper by AOES scientists Tim DelSole, Laurie Trenary, and Kathy Pegion in collaboration with Michael Tippett of Columbia University.
Back in the 1960s, Ed Lorenz discovered that chaos made daily weather impossible to predict more than a few weeks in advance. In recent decades, researchers at COLA and elsewhere have been studying how the land and ocean may allow prediction of seasonal averages months or longer in advance. However, forecasting 3-4 weeks in advance has been traditionally considered a kind of “predictability desert” that is too far in the future for weather forecasts and too short for climate forecasts. DelSole et al. use a sophisticated statistical approach to find that NOAA’s Climate Forecast System has significant skill at 3-4 weeks for large swathes of the United States. As noted in the paper, skillful forecasts in this range “would have significant social and economic value because many management decisions in agriculture, food security, water resources, and disaster risk are made on this time scale.”
AOES Climate Dynamics PhD students Guangyang Fang and Keri Kodama were each awarded competitive summer research stipends by the GMU Provost’s office.
In 2014, climate models were predicting the onset of a powerful El Nino, the disturbance in the equatorial Pacific ocean and atmosphere that disturbs weather across the globe. Then the expected El Nino fizzled, only to appear the following year with record heat. Kodama has received a Summer Presidential Scholar Fellowship to work with her advisor, AOES faculty member Natalie Burls, on research related to improving El Nino predictions. She has been using satellite data to analyze the transfer of energy that occurs when wind blows across the ocean. This energy transfer may be an important precurser for El Nino.
Climate variability is not limited to the Pacific. Tropical Atlantic Variability (TAV) consists of changes from year to year in sea surface temperature which can influence climate in surrounding regions. Guangyang Fang has received a Summer Research Fellowship to work with AOES faculty member Bohua Huang on the causes of TAV. He will be conducting predictability experiments with a global climate model to determine whether the various TAV events are predictable on seasonal time scale. These experiments can also be used to understand the TAV’s connection to climate phenomena external to the Atlantic, including El Nino.
Climate Dynamics doctoral student Holly Norton was awarded a competitive Summer Student Internship at the NOAA National Centers for Environmental Prediction (NCEP). She will be working at the NOAA Center for Weather and Climate Prediction in College Park, Maryland. At NCEP, she will be working to improve the land component of climate models. The models calculate the movement of water below the land surface, which affects the availability of soil moisture. The soil, in turn, interacts with the atmosphere. The work is related to Holly’s PhD dissertation and builds on her academic background in both climate dynamics and geology.