The Potential for Triggered Seismicity Associated With Geologic Sequestration of CO2 in Saline Aquifers (Invited)
It is well known that for geologic sequestration of CO2 to play a significant role in greenhouse gas reduction it must operate at enormous scale. (Pacala and Socolow, Science 2004) pointed to a number options that could lead, by mid-century, to stabilization of CO2 in the atmosphere at about 550 ppm (roughly twice pre-industrial levels). For geologic sequestration of CO2 to play a significant role in a global strategy for greenhouse gas reduction, it must account for about a billion tons of carbon per year - about the same mass as total annual global oil production. A number of reports have addressed the expense associated with such an undertaking. In addition to the high capital and operating costs associated with equipping thousands of industrial plants with CO2 separation and capture equipment (coal burning power plants, refineries, cement plants, etc.), the transport, injection and long-term monitoring costs associated with large scale CO2 sequestration are formidable. Beyond economics, there is a potentially serious geological issue that threatens the viability of large scale CO2 sequestration which may not be technically solvable, at any cost - the likelihood that injection of enormous volumes of CO2 into the subsurface will trigger intraplate earthquakes. A number of lines of evidence indicate that to first-order, the Earth's brittle crust, even in intraplate regions, is in a state of frictional failure equilibrium. Earthquakes occur almost everywhere in intraplate areas around the world in response to regional plate-driving forces. At any given intraplate site, expected natural earthquakes that might be small enough and infrequent enough that it is safe for critical facilities such as nuclear power plants to operate for periods on the order of 50-100 years. Because there have been so many documented cases where fluid injection has disturbed the frictional-equilibrium of the crust and triggered earthquakes almost always relatively small. While the seismic waves from such earthquakes might not directly threaten the public, small earthquakes at depth could threaten the integrity of a CO2 repositories, expected to store CO2 for periods of hundreds to thousands of years.
Real-time Seismicity Evaluation as a Tool for the Earthquake and Tsunami Short-Term Hazard Assessment (Invited)
Seismic activity is a 3-D process varying in the space-time-magnitude domains. When in a target area the short-term activity deviates significantly from the usual (background) seismicity, then the modes of activity may include swarms, temporary quiescence, foreshock-mainshock-aftershock sequences, doublets and multiplets. This implies that making decision for civil protection purposes requires short-term seismic hazard assessment and evaluation. When a sizable earthquake takes place the critical question is about the nature of the event: mainshock or a foreshock which foreshadows the occurrence of a biger one? Also, the seismicity increase or decrease in a target area may signify either precursory changes or just transient seismicity variations (e.g. swarms) which do not conclude with a strong earthquake. Therefore, the real-time seismicity evaluation is the backbone of the short-term hazard assessment. The algorithm FORMA (Foreshock-Mainshock-Aftershock) is presented which detects and updates automatically and in near real-time significant variations of the seismicity according to the earthquake data flow from the monitoring center. The detection of seismicity variations is based on an expert system which for a given target area indicates the mode of seismicity from the variation of two parameters: the seismicity rate, r, and the b-value of the magnitude-frequency relation. Alert levels are produced according to the significance levels of the changes of r and b. The good performance of FORMA was verified retrospectively in several earthquake cases, e.g. for the L’ Aquila, Italy, 2009 earthquake sequence (Mmax 6.3) (Papadopoulos et al., 2010). Real-time testing was executed during January 2010 with the strong earthquake activity (Mmax 5.6) in the Corinth Rift, Central Greece. Evaluation outputs were publicly documented on a nearly daily basis with successful results. Evaluation of coastal and submarine earthquake activity is also of crucial importance for the short-term hazard assessment for near-field tsunamis, given that the time constraints for early warning is on the order of few minutes up to less than 1 hour. It is proposed that warning procedures for near-field tsunamis in a target area may benefit by combining a tsunami decision matrix with short-term seismic hazard evaluation. Simulated procedures incorporating retrospective tests in the Mediterranean Sea proved encouraging.
Drilling into Faults Quickly After Earthquakes (Invited)
What will it take to advance from our current empirical model of earthquake initiation and fault slip, to a full physics-based understanding of the rupture process? We need to know the absolute stress levels on the fault during an earthquake, how the stresses recover afterwards to prepare for the next event, how one earthquake promotes or inhibits another, and how the material properties of a particular fault affect its propensity to fail catastrophically, rather than creep. Immediately after a large earthquake, there is an opportunity to gain crucial information to fill these gaps in knowledge. For about two years after a major earthquake, the fault is observably changing and a deep borehole can capture measurable signals. For instance, the strength of faults and their time and slip dependence are generally unknown, especially for large displacements and high slip velocity. Current laboratory evidence suggests that friction could drop dramatically during an earthquake, but the actual fault friction levels of a large earthquake have never been measured. Temperature profiles across the fault are the most direct way to quantify coseismic friction. Because most of the frictional resistance is dissipated as heat, any temperature increase on the fault at the time of the earthquake is potentially interpretable as a cumulative measure of frictional heat generation during slip. To obtain the largest and most unambiguous signal possible, it is critical to record these measurements both soon after earthquake slip, and at depths where shear stress (a function of the effective normal stress and the effective coefficient of friction) is sufficiently large to generate an observable temperature anomaly. Model calculations suggest that a borehole drilled to 2 km depth within 1.5 years after an earthquake with >1 m surface displacement should be sufficient to observe a resolvable temperature signal. Similar constraints apply for other major data needs. Combining the constraints results in a preferred timetable of drilling initiating within 6 months after the earthquake and intersect the fault at 2 km depth within 1.5 years. Although major advances in earthquake physics projects have been made from previous rapid drilling projects on the Nojima, Chelungpu and Wenchuan Faults, a hole that meets these more stringent target requirements has not yet been completed.
Constraining the climate sensitivity of the global carbon cycle with paleoclimatic data (Invited)
The processes controlling the carbon flux and storage of the atmosphere, ocean, and terrestrial biosphere are temperature sensitive and are likely to provide a positive feedback leading to amplified anthropogenic warming. Due to this feedback, at interannual to Milankovitch timescales, warming of the climate system causes a net release of CO2 into the atmosphere; this in turn amplifies warming. But the magnitude of the climate sensitivity of the global carbon cycle - termed γ- and thus of its positive feedback strength, is under debate, giving rise to large uncertainties in global warming projections. In this talk, I will present recent work based on coupling a probabilistic approach with an ensemble of proxy-based temperature reconstructions and pre-industrial CO2 data to provide robust constraints for γ on the policy-relevant multi-decadal to centennial timescales. We quantify the median γ to 7.7 ppmv CO2/°C warming with a likely range of 1.7 - 21.4 ppmv CO2/°C. Sensitivity experiments exclude significant influence of pre-industrial land-use change on these estimates. By employing an ensemble of >200,000 members, quantification is not only improved, but likelihoods can be assigned, thereby providing a benchmark for model simulations. Although uncertainties do not presently allow exclusion of γ calculated from any of ten coupled carbon-climate models, we find that γ is about twice as likely to fall in the lowermost rather than uppermost quartile of their range. Our results are incompatibly lower (p<0.05) than recent pre-industrial empirical estimates of ~40 ppmv CO2/°C and correspondingly suggest ~80% less potential amplification of ongoing global warming.
Is Hurricane Activity in One Ocean Basin Tied to Another? (Invited)
In the Western Hemisphere, tropical cyclones (TCs) or hurricanes can form and develop in both the tropical North Atlantic and eastern North Pacific Oceans, which are separated by the landmass of Central America. It is shown that TC activity in the North Atlantic varies out-of-phase with that in the eastern North Pacific on seasonal, interannual and multidecadal timescales. That is, when TC activity in the North Atlantic increases (decreases), TC activity in the eastern North Pacific decreases (increases). We show that both tropospheric vertical wind shear and convective instability contribute to the out-of-phase relationship, whereas relative humidity and vorticity variations at the lower troposphere do not seem to cause the relationship. Both observational data and atmospheric general circulation model runs show that the variations of the Atlantic warm pool can produce the out-of-phase relationship between TCs in the North Atlantic and eastern North Pacific. Other climate influences, such as ENSO and the Atlantic multidecadal oscillation, will also be discussed. An implication of this research is that seasonal hurricane outlook can be improved by considering the North Atlantic and eastern North Pacific together.
Ocean-Atmosphere Coupling associated with Typhoons/ Hurricane and their impacts on marine ecosystem (Invited)
DanLing TANG South China Sea Institute of Oceanology, Chinese Academy of Sciences,Guangzhou, China Phone (86) 13924282728; Fax/Tel: (86) 020 89023203 (off), 020 89023191 (Lab),Email,email@example.com, Typhoon / hurricane activities and their impacts on environments have been strengthening in both intensity and spatial coverage, along with global changes in the past several decades; however, our knowledge about impact of typhoon on the marine ecosystem is very scarce. We have conducted a series studies in the South China Sea (SCS), investigating phytoplankton, sea surface temperature (SST), fishery data and related factors before, during, and after typhoon. Satellite remote sensing and in situ observation data obtained from research cruise were applied. Our study showed that typhoon can support nutrients to surface phytoplankton by inducing upwelling and vertical mixing, and typhoon rain can also nourish marine phytoplankton; both typhoon winds and rain can enhance production of marine phytoplankton. Slow-moving typhoon induced phytoplankton blooms of higher Chlorophyll-a (Chl-a), the strong typhoon induced phytoplankton blooms of a large area. We conservatively estimate that typhoon periods may account for 3.5% of the annual primary production in the oligotrophic SCS. It indicated that one typhoon may induce transport of nutrient-rich water from depth and from the coast to offshore regions, nourishing phytoplankton biomass. More observations confirmed that typhoon can induce cold eddy, and cold eddy can support eddy-shape phytoplankton bloom by upwelling. We have suggested a new index to evaluate typhoon impact on marine ecosystem and environment. This is the first time to report moving eddies and eddy-shape phytoplankton blooms associated with tropical cyclone, the relationship among tropical cyclone, cold eddy upwelling and eddy-shape phytoplankton bloom may give some viewpoint on the tropical cyclone's affection on the mesoscale circulation. Those studies may help better understand the mechanism of typhoon impacts on marine ecosystem, and the role of typhoon in the global environmental changes. The present research was supported by the following grants awarded to D.L.TANG: (1) National Natural Science Foundation of China (40976091, 40811140533) and Guangdong Natural Science Foundation, China (8351030101000002); (2) Chinese Academy of Sciences (kzcx2-yw-226 and LYQ200701);
Use of UAVs in extreme environments: UAV observations of the Antarctic atmosphere and surface during winter (Invited)
Aerosonde unmanned aerial vehicles (UAVs) were used during the late Antarctic winter (September 2009) to observe the atmosphere and ocean / sea ice surface state in the vicinity of Terra Nova Bay, Antarctica. These flights were the first wintertime UAV flights ever made in the Antarctic, and were also the longest duration UAV flights made to date in the Antarctic, with a maximum flight time of over 17 hours. A total of 130 flight hours were flown during September 2009, with a total of 8 science flights to Terra Nova Bay. The flights took place at the end of the Antarctic winter, in an environment characterized by strong katabatic winds in excess of hurricane strength. Atmospheric and surface observations acquired with the UAV will be presented. The advantages of using UAVs in extreme environments as well as the logistical challenges of operating UAVs in the Antarctic winter will also be presented.
Aerosonde UAV being launched from a pickup truck at Pegasus white ice runway, Antarctica.
Temporal and spatial variability, and extreme events of the Great Lakes ice cover: Impacts of ENSO and AO (Invited)
Seasonal and interannual variability of lake ice cover in the Great Lakes is investigated using historical and satellite measurements for the period 1973-2010. After climatology of the seasonal cycle is derived for lake ice season, large anomalous interannual variability is found in response to atmospheric teleconnection patterns. Nevertheless, spatial variability of ice cover in the five Great Lakes shows regional differences and characteristics. A principal-component or EOF (empirical orthogonal function) analysis is applied to lake ice anomalies to derive major spatial and temporal patterns, which can be explained by major atmospheric variability controlled by well-known climate patterns: Arctic Oscillation (AO) and ENSO (El Nino and Southern Oscillation). Thus, a normalized ice anomaly index is derived by combined five Great Lakes ice normalized by its individual standard deviation, which can be used to be regressed atmospheric forcing field. Lake ice reduction rate over the last three decades in each lake is estimated. Dynamic mechanisms controlling lake ice temporal and spatial variability are investigated in the context of regional climate changes. The extreme events such as 2008-09 and 2009-2010 ice seasons were used to demonstrate the role of ENSO and AO on ice variability in the Great Lakes.