2019-2020 Seminars

Geology Seminars Spring 2020

3301 Exploratory Hall, 4:30 – 5:30 pm, except as noted

Wed. Jan 29, 11:00-12:00, EX 1309 – Jonathan Hammer, GMU: Review of Basic Concepts of Kalman Filtering
Thurs. Jan 30 – Jonathan Tucker, Carnegie Institution: Deep Earth volatiles
Thurs. Feb 13 – Natalie Burls, GMU: THC in the Pliocene Pacific Ocean
Thurs. Feb 27 – Ved Lekic, University of Maryland, College Park: Global Seismology
Thurs. Mar 19 – Matt Powell, Juniata College, Paleozoic brachiopods
Thurs. Apr 2 – Jerry Burgess, Johns Hopkins University: Geo-ecosystem structure and dynamics
Thurs. Apr 16 – Soumaya Belmecheri, NSF: Trees, fire and climate change
Thurs. Apr 30 – Bronwen Konecky, Washington University: Tropical paleoclimate

Geology Seminars Fall 2019

4:30 – 5:45 pm Thursdays, 1309 Exploratory Hall (the Paleo Lab)

September 5 – Shi Joyce Sim, Carnegie: Early Earth; planetary formation
September 19 – Megan Newcombe, Carnegie/Maryland: Volcanism on Earth, Moon, Mars
WEDS., October 2 – Alan Pitts, University of Camerino: GMU Field Camp
October 3 – Mong-Han Huang, Maryland: Ridgecrest and Kilauea seismicity
October 17 – Gene Hunt, Smithsonian: ostracod evolution
October 31 – Erica Suosaarie, Smithsonian: carbonates and stromatolites
November 14 – Mike Evans, Maryland: “PAGES (Past Global Changes) 2K projects, past, and future”

All seminars at 1:30pm on Wednesday unless otherwise noted.

Aug 28: Tim DelSole (George Mason University)
New Developments in Model Selection, or A New Way to Not Fool Yourself
The Hub Room 1

I will introduce the concept of model selection and discuss some new developments that have important implications for modeling climate data. Some topics that will be covered include: proper scores, Akaike’s Information Criterion, Canonical Correlation Analysis, and Linear Inverse Models.

11 Sep: Cristina Stan (George Mason University)
On the Subseasonal-to-seasonal variability of Extra-tropics
Research Hall 163

Recent advancements in understanding the subseasonal-to-seasonal (S2S) variability outside of the tropics will be discussed. I will introduce the multi-channel singular spectral analysis (MSSA) method used to isolate the S2S variability in the extra-tropics, present the oscillatory modes dominating the extra-tropics on these time scales and their relationship with tropical variability, and discuss the implications for midlatitude oscillatory modes for the predictability at Week 3&4.

16 Sep: Current Climate Conversation
Monday, Noon, Research Hall 121 – NOTE NEW TIME

Quasi-monthly AOES discussion of notable recent climate and weather events. Come with an interesting news item. Come to add your two cents. Or just come to listen.

18 Sep: Jianzhi Dong (USDA-ARS Hydrology and Remote Sensing Lab)
Constraining land surface modeling uncertainty using remotely sensed soil moisture and evapotranspiration coupling strength
Johnson Center Meeting Room B

Modeled soil moisture (SM) and evapotranspiration (ET) coupling strength contain substantial uncertainties, which complicates land data assimilation and short-term numerical forecasting. For example, improved SM may degrade ET and air temperature estimates, if the model system is biased in SM-ET coupling strength. To physically constrain such modeling error, we proposed a global reference map of SM-ET coupling strength by leveraging multi-source SM and ET estimates. We further used this reference SM-ET coupling strength map for land surface model (LSM) optimization. Results demonstrate that this coupling strength based optimization simultaneously improves SM and ET estimates. Such improvement cannot be achieved by calibrating LSM-based SM and ET time series. Therefore, SM-ET coupling strength is a more physically based constrain for reducing LSM uncertainties, and may improve future development of LSM model structure and parameterization.

25 Sep: D. Benson, P. Buchmann, A. al-Fahad (George Mason University)
Climate Dynamics Student Talks
Johnson Center Meeting Room D

2 Oct: Paul Ginoux (NOAA Geophysical Fluid Dynamics Lab)
Mineral dust interactions with the Earth’s Climate System: A modeling perspective
Johnson Center Meeting Room D

Mineral dust is a key agent in a variety of processes driving the different components of the Earth’s Climate System. Comparison with observations indicates that models have particular difficulties to reproduce low-frequency variability of dynamically emitted aerosols such as mineral dust. I will show that this appears to be related to the lack of dependency on vegetation changes in response to perturbations in the hydrological cycle. The new GFDL Earth’s System Model (ESM) contains fully interactive and consistent dust life-cycle. This seminar will present an analysis of the amplification of dust forcing by vegetation and land-use changes, and how it helps reproduce low-frequency variability. Still the amplitude and even the sign of dust impacts on climate and hydrology depend on poorly constrained parameters, such as mineralogy, as I will show. I will describe a NASA-funded project to retrieve such parameters globally from space.

7 Oct: Natalie Burls (George Mason University)
What can the ocean floor tell us about the top of the atmosphere millions of years ago and in the centuries to come?
Mon, noon, Johnson Center Meeting Room D

Estimating the sensitivity of climate to increases in CO2 concentration is one of the grand challenges in climate science. Extensive research has revealed three main obstacles: the model-, time-, and state-dependent nature of climate feedback processes, most of all those due to highly uncertain changes in clouds. For decades, successive generations of climate models displayed a similar range of sensitivities. Several of the latest generation (CMIP6), which include more sophisticated cloud microphysics and other advances, show higher sensitivity–above the spread that has been seen since the 1970s. Can observations offer guidance on the plausibility of these higher climate sensitivities? The instrumental record is limited by its short time span, but sediments on the ocean floor contain millions of years of data. In this talk, we will turn to the past warm climates of the Cenozoic for clues on how clouds and the hydrological cycle change under warming. We will examine the implications of cloud forcing and feedback strength for key features of Earth’s climate in a range of climate model sensitivity experiments, and compare these with surface temperature and hydrological cycle reconstructions from these past warm climates.

9 Oct: Zhanqing Li (U Maryland)
Aerosol’s impact on earth’s energy and water cycles:Implications for climate changes and extreme weather events
Johnson Center Meeting Room D

Aerosol particles can have a wide range of impacts on weather and climate. By reducing solar radiation reaching ground and increasing cloud reflection (the Twomey effect), they may offset the warming due to greenhouse gases. On the other hand, they may also increase the area of cirrus clouds to incur a warming effect. Ample evidence shows the impact of aerosol on such extreme weather events as flood, thunderstorms, and lightning on time scales ranging from diurnal to decadal. Such evidence, however, is often tangled with meteorological variability that may not be readily detangled, making it one of most challenging problem in earth sciences. As a result, the number of aerosol-related studies has increased nearly exponentially since 1990s. I will present both an overview and major advancement in aerosol related studies, especially from the viewpoint of east Asia.

16 Oct: Ichiro Fukumori (NASA Jet Propulsion Lab)
Exploring Mechanisms of Ocean Circulation Combining Observations and Models
Johnson Center Meeting Room D

Observations are often sparse and limited in scope. Models can combine and interpolate these data into complete descriptions of the ocean. Such combination, known as data assimilation and/or state estimation, permits studies that can otherwise be difficult. This talk will illustrate examples of such using products of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO http://www.ecco-group.org/). ECCO provides the community a resource for studying the ocean by combining nearly all extant observations with a global ocean general circulation model. The model’s adjoint, in particular, used in the combination, is an effective tool in identifying causal mechanisms. I will review these tools and products of ECCO and how one might use them in furthering our understanding of the ocean.

17 Oct: Kathleen Pegion (George Mason University)
Advancing Subseasonal and Seasonal Predictions
Thu, noon, Johnson Center Meeting Room A

Reliable probabilistic forecasts of short-term climate variability are valuable for routine planning and resource management. Many sectors would benefit from these predictions, including emergency management, public health, energy, water management, agriculture, and marine fisheries. The ability to make skillful forecasts on subseasonal (2-4 week) and seasonal (1-12 months) lead-times depends on understanding and harnessing the predictive capabilities of key sources of predictability.

I will present results from two research projects which are advancing our predictive capabilities on these timescales. First, I demonstrate the potential to extend the lead time of predictions of the El Nino-Southern Oscillation as long as one-year in advance based on mechanisms originating in the Northern and Southern Hemisphere extratropics. Second, I demonstrate the current state of subseasonal prediction skill and the benefit of a multi-model ensemble using a national, multi-model, research to operations project called The Subseasonal Experiment (SubX). Additionally, I investigate the skill and potential sources of errors for three sources of subseasonal predictability, the Madden-Julian Oscillation, the North Atlantic Oscillation, and air-sea interactions associated with ocean mesoscales eddies.

23 Oct: Jim Carton (University of Maryland)
Using ocean observations to improve estimates of net surface fluxes
Johnson Center Meeting Room D

Surface exchanges of heat, mass, and momentum are core environmental variables, but remain surprisingly uncertain. Historically these exchanges have been estimated by closing budgets using data extracted from an atmospheric reanalysis. Large uncertainties in the exchange estimates arise because of the complexity of atmospheric processes, presence of compensating errors, and the weakness of the exchanges as a constraint on the atmosphere. In the past decade the ocean observing system has improved so much that now it makes sense to consider the alternative of estimating surface fluxes by closing the ocean heat, mass, and momentum budgets. Estimating the exchanges through the ocean budgets has additional advantages, including lower Rossby numbers and weaker diabatic processes. In this talk I discuss how one can infer net heat and freshwater fluxes from output from an ocean reanalysis using sequential data assimilation and illustrate the procedure with examples from the Simple Ocean Data Assimilation.

28 Oct: Current Climate Conversation
Mon, noon, Research Hall 121

Quasi-monthly AOES discussion of notable recent climate and weather events. Come with an interesting news item. Come to add your two cents. Or just come to listen.

30 Oct: H. Hsu, O. Gozdz, D. Nedza (George Mason University)
Climate Dynamics Student Talks
Tentative room: Research 163

6 Nov: Tripti Bhattacharya (Syracuse University)
Insights into future Central American drying from paleoclimatic proxies
Research Hall 163

Central America, the Caribbean, and parts of Mexico, which have historically experienced devastating droughts, are predicted to dry in the 21st century as a result of anthropogenic warming. In this talk, I use the paleoclimatic record to study dynamical processes relevant to future projections. Using a synthesis of proxy indicators of hydroclimate and last millennium model simulations, I show that past dry intervals were likely the result of changes in tropical North Atlantic (TNA) temperatures, which altered patterns of atmospheric moisture convergence. I also show that the model spread in rainfall projections is strongly related to the magnitude of TNA warming in each model, suggesting that past and future hydroclimate change are driven by similar mechanisms. These results suggest that analyses of the dynamics of past dry intervals can directly contribute to a better understanding of future drying in this climate change hotspot.

12 Nov: Keri Kodama (George Mason University)
Climate Dynamics Doctoral Defense
The El Nino-Southern Oscillation from an Empirical Adjusted Energetics Perspective
Tue, 9am, Johnson Center Meeting Room E

Dissertation Abstract

21 Nov: Kevin Grise (University of Virginia)
Understanding the two-way interactions between cloud radiative effects and the midlatitude storm tracks
Thu, 1:30
New Room: Johnson Center Gold Room (basement level, follow signs from Cinema)

Global climate models indicate that the atmospheric response to increasing greenhouse gases is not limited to an increase in the global-mean surface temperature: for example, the midlatitude storm tracks shift poleward, the Hadley circulation expands, and consequently the hydrological cycle is altered. The linkages among these changes in the atmospheric circulation, cloud feedbacks, and climate sensitivity remain poorly understood. In this talk, I will explore these linkages in the context of the midlatitude storm tracks. In many climate models, a poleward storm track shift is associated with a positive cloud feedback, as storm track clouds move to a higher latitude where they reflect less sunlight. Clouds also play a role in driving the midlatitude storm tracks. Idealized model experiments show that the high-frequency interactions between cloud radiative effects and the dynamics of the storm tracks slightly damp the intensity of the storm tracks. The coupling among clouds, radiation, and dynamics thus has a modest but potentially important influence on the midlatitude storm tracks.

25 Nov: Current Climate Conversation
Mon, noon, Research Hall 121

Quasi-monthly AOES discussion of notable recent climate and weather events. Come with an interesting news item. Come to add your two cents. Or just come to listen.

4 Dec: Derrick Lampkin (U Maryland)
Greenland’s Shear Margins in Warming Climate: A Summary of Recent Work
Research Hall 163

The Greenland Ice Sheet has experienced unprecedented changes in the couple decades resulting from regional warming resulting in enhanced surface melting. The increased in melting has activated a dynamic surface hydrologic system contributing to significant mass loss. Surface melt runoff contributes directly to Greenland’s mass loss as well as infiltration which impact ice dynamics and mass discharge. The ice sheet has a few critical bounding forces that can influence the rate of mass loss which includes the loss of ice shelves/tongues, enhanced calving at marine-terminating outlet glaciers, and an evolving basal hydrologic system due to infiltration of surface melt. In particular, the impact of surface melt water on ice dynamics via supraglacial lake drainage and runoff has been well documented. Little attention has been focused on direct injection of surface melt water into the shear margins of fast flowing, marine-terminating outlet glaciers, which are a critical control on mass flux. Our initial work was the first to characterize water-filled crevasse ponds within the shear margins of Jakobshavn Isbræ and assessment the volume of infiltrated melt water potentially reaching the bed. In the intervening years since this seminal work, we have utilized satellite observations and numerical models to decode the impact of hydrologic shear weakening due to melt water injection from these structures with implications for the evolution of Greenland’s other marine-terminating outlet glaciers under a warming climate.

16 Dec: Susanna Corti (Institute of Atmos. Sci. & Climate, Italy)
North-Atlantic wintertime Weather Regimes in coupled historical climate simulations: Model performance and improvements with increased resolution
Mon, 2pm, Research 163

Understanding future changes in the variability of the climate system is particularly challenging in mid-latitude regions like the North-Atlantic, which has large natural variability and is intrinsically difficult to predict. Weather Regimes (WRs) constitute a suitable framework for studying variability of the atmospheric circulation. They are recurrent geopotential patterns which influence regional weather and extremes over Europe. We use Weather Regimes to analyze historical simulations at two resolutions in state-of-the-art climate models. We find that higher resolution models better represent the WR structure (patterns and significance) but not their persistence and frequency of occurrence. Finally, we analyze the connection of the WRs with the Jet Stream latitude and blocking frequency anomaly.

[18 Dec: Current Climate Conversation] – CANCELLED
Wed, noon, Research Hall 121

Quasi-monthly AOES discussion of notable recent climate and weather events. Come with an interesting news item. Come to add your two cents. Or just come to listen.