MIT Reports to the President 1998-99

DEPARTMENT OF EARTH, ATMOSPHERIC AND PLANETARY SCIENCES

The Department of Earth, Atmospheric, and Planetary Sciences (EAPS) has broad intellectual horizons that encompass the solid earth, its fluid envelopes, and its diverse neighbors throughout the solar system and beyond. We seek to understand the fundamental processes defining the origin, evolution and current state of these systems and to use this understanding to predict future states. The Department comprises 38 faculty, including two with primary appointments in Civil and Environmental Engineering, 221 graduate and undergraduate students, and 133 research staff, postdoctoral appointments and visiting scholars. EAPS is notable for its collaborations with other MIT Departments and Schools to address complex interdisciplinary problems.

EAPS has vigorous graduate educational programs in geology and geochemistry, geophysics, atmospheres, oceans, climate, and planetary science. Each disciplinary area of EAPS continues to be ranked among the top graduate programs in the country, with most areas being rated either first or second nationally. The EAPS graduate program currently focuses on the Ph.D. degree, which is the goal of about 90 percent of its graduate students. During the past academic year, 166 graduate students were registered in the Department including EAPS students in the MIT/Woods Hole Oceanographic Institution (WHOI) Joint Program. Of these 108 are U.S. citizens and 58 are international students. Women constitute 38 percent of the graduate student population. 33 Ph.D. and 20 S.M. degrees were awarded during the past academic year.

The new EAPS Master's Degree Program in Geosystems graduated its second class this year. The program's novel curriculum is designed to educate geoscientists in system-level analysis and prepare them for professional careers in high-technology industries concerned with complex geosystems. The degree requirements comprise 108 units of course work, including the novel two-semester, 30-unit Geosystem basetrack subject, and a master's thesis. All seven of the entering students successfully completed the course work in two semesters; four graduated in June, and the other three are expected to finish their theses by the end of the summer.

Another recent exciting educational initiative has been the establishment of the Program in Atmospheres, Oceans and Climate (PAOC), which coordinates graduate study in atmospheric science, oceanography, and climate physics and chemistry. The Program, which is directed by Professor Wunsch, offers a broadly based curriculum for students interested in studying climate at the system level, and in performing research in oceanography and atmospheric science. The department now offers the Ph.D. in Climate Physics and Chemistry with 12 students currently enrolled. Enrollment in the PAOC graduate degree programs continues to slowly increase. Various faculty departures now present a challenge for us to sustain the breadth of the PAOC program, which is arguably unique in the world.

A bi-annual prize has been developed to recognize and reward the efforts of outstanding EAPS Graduate Teaching Assistants. Winners during the past year include Frederik Simons, Jessica Neu, Arthur White, John Thurmond, Mark Schmitz and Bill Lyons. Professor Kip Hodges served as Dean for Undergraduate Curriculum over the past year and played an active role in the redesign of MIT's freshman-year academic program through his co-chairmanship of the CUP-ODSUE Educational Design Project.

EAPS continues to maintain a strong presence within the undergraduate program at MIT. The Department continues to offer a wide variety of Freshman Advising Seminars each Fall with 10 faculty members participating each of the past two years, advising almost 10 percent of MIT's freshman class. A new undergraduate seminar has been developed to introduce newly declared sophomore majors to the broad research interests of the faculty. This seminar was very well received during its inception and is now being modified and expanded to include one-on-one mentoring by faculty members in the areas of technical writing and oral communication.

The EAPS Independent Activities Program (IAP) continues to be one of the most vibrant at MIT, and faculty have maintained a healthy Undergraduate Research Opportunities Program (UROP). This past year, 4 majors were able to travel to Mauna Kea, Hawaii where they had and a weeks worth of observing time on the 24-inch telescope allowing them to acquire professional quality data for their bachelor's theses. Oceanography students spent IAP at the Caribbean Marine Research Center on Lee Stocking Island, Bahamas focusing on observational, measurement, and analytical techniques used by professionals in their discipline. Geoscience students traveled to field camp in Nevada where they obtained first-hand experience in modern stratigraphic and cartographic mapping techniques.

The Bachelor of Science curriculum was reorganized several years ago to include three areas of concentration: geoscience, physics of atmospheres and oceans, and planetary science and astronomy. Each concentration encompasses a set of required courses, a sequence of field and laboratory subjects, and independent study or thesis preparation. Historically, students have primarily chosen to specialize in either geoscience or planetary science and astronomy. In the past two years however, there have been an increasing number of students (now totaling 6) pursuing studies in the physics of atmospheres and oceans. Within this concentration area, a new Institute Lab course has been developed (12.307) that will permit undergraduates to develop and perform experiments related to the general circulation of the atmosphere and the day-to-day sequencing of weather events.

Professors Richard Binzel and Samuel Bowring were promoted to Full Professor and Professor Robert van der Hilst was promoted to Associate Professor with Tenure. Professor John Grotzinger was named the new Director of the Earth Resources Laboratory, succeeding Professor M. Nafi Toksöz who stepped down after 17 years to focus on research and teaching.

Professor Ronald Prinn, who completed his first year as Department Head of EAPS, was elected Chair for Atmospheric and Hydrospheric Sciences of the American Association for the Advancement of Science.

Professor Paola Rizzoli was awarded the Masi Prize of the Italian Ministry of Arts and Culture. Professor John Edmond won the Urey Medal of the European Association of Geochemists this year. Professor Robert van der Hilst received the 1998 Packard Fellowship. Professor Samuel Bowring was elected as Fellow of the Geological Society of America this past year. Professor Edward Boyle was elected a Fellow of the Geochemical Society/European Association of Geochemistry. Professor Bras was the Horton Lecturer of the American Meteorological Society.

Professor Mario Molina was awarded the ACS Award for Creative Advances in Environmental Science and Technology and the Willard Gibbs Medal of the American Chemical Society this past year. He also received Honorary degrees from Occidental College (CA) and from Connecticut College and was named an American Geophysical Union Fellow and an American Physical Society Fellow.

The Department has active faculty searches in three exciting areas. The first is in Planetary Science which is making dramatic advances toward understanding the formation and evolution of our solar system and other planetary systems. Observations made using recent advances in both spacecraft and earth-based sensors are enabling the development of more physically realistic models of dynamical interactions between planetary bodies, as well as the internal constitution and thermal history of individual planets and their moons. In some cases modeling of global-scale planetary processes is becoming feasible, and comparisons to Earth will ultimately be possible. The study of small bodies, particularly in the Kuiper belt, is extending our understanding of the far reaches of the solar system and promises to yield insight into the nature of objects that accumulated to form the planets.

The second faculty search is in Crustal Geophysics. Of growing importance is the need for advances in our understanding of the structures and processes of the upper crust, particularly for solving problems of relevance to industry and society. Areas that have been identified as being particularly fertile at this time include 3-D and 4-D seismic imaging, electromagnetic wave propagation, flow through porous media, sediment transport dynamics, and reservoir structure. Also of interest are the relationships among subsurface structures imaged using state-of-the-art seismology and the kinematics and dynamics of crustal deformation as determined from space geodesy, geology, and numerical models. All these areas are relevant to present and planned new activities in the Earth Resources Laboratory, including new research towards understanding the physical processes that lead to heterogeneity in petroleum reservoirs

The third faculty search is in Geobiology. We envision this emerging new field to encompass research that includes the origin of life, evolutionary and developmental biology, microbial biology, and the interactions between ecosystems and climate. There are numerous opportunities for interactions and collaborations between the person hired for this position and faculty in our programs in climate, planetary geology, and earth geology as well as the Civil and Environmental Engineering and Biology Departments. The time is right for the expansion of the department into this new field, which is important to much of the research currently carried out in the department.

The Department continues to pioneer work in new interdisciplinary areas. The Center for Global Change Science (including the Climate Modeling Initiative) and the Program in Atmospheric, Oceans and Climate continue to foster cross-fertilization among all areas of the earth sciences that control the climate system. Research activities are gradually broadening so that, as hoped, geologists are working with oceanographers and atmospheric scientists, and models of the climate system have been constructed both for the modern system and for times deep in the geological past. A new faculty group interested in co-evolution of the geosphere and biosphere has formed and is focussing initially on understanding the great extinctions in earth's past. Department faculty also continue to play leading roles in the MIT Joint Program on the Science and Policy of Global Change.

Professor Samuel Bowring continued his work on the origin and evolution of continental lithosphere and on using high-precision U-Pb geochronology to constrain major events in biological evolution such as the Cambrian radiation and the end-Permian extinction. Professors Bowring and Grotzinger are part of NASA's newly initiated Astrobiology Institute which is focussed on understanding the planetary context of biological evolution.

Professor Clark Burchfiel spent last May and June in the eastern and southeastern part of the Tibetan plateau studying the uplift and formation of the Tibetan plateau and how the river drainage system off the plateau has been shaped and reshaped by tectonic and climatic effects.

Professor Frederick Frey was co-chief scientist on an ocean drilling expedition which focussed on understanding the formation of the Kerguelen Plateau. Major results are: (1) although now 1 to 2 km below sea level, this region was above sea level when it formed; (2) although largely a basaltic plateau, the volcanism ended with explosive volcanism that probably had significant environmental consequences; (3) although formed in an oceanic environment, continental rocks which are ancient fragments of Gondwana were incorporated into the Indian Ocean seafloor during breakup of eastern Gondwana.

Professor John Grotzinger has been focussed on continuing his research on understanding the geobiological factors that lead to the adaptative radiation of early Cambrian animals. This work has centered on geological and paleontological research in Namibia where his research team has made recent discoveries of the world's oldest skeletonizing invertebrates.

Professor Tim Grove and colleagues have been determining rates for solid state diffusion of trace elements in mantle minerals at temperatures and pressures relevant for melting in the Earth's interior. They find that the diffusion rates for the rare earth elements are extremely slow and vary systematically with ionic radius. Diffusion for some rare earth elements is slow enough that the interior of a crystal will remain out of equilibrium with the melt that contacts the crystal. This disequilibrium effect is being used to derive the first quantitative estimates of the rates of melt extraction in the source regions of basalts.

Professor Kip Hodges and his students continued their research into the evolution of mountain ranges through integrated field and laboratory studies of the Caledonides of East Greenland and the Nepalese Himalaya. Their recent work in central Nepal–in collaboration with Professor Kelin Whipple–demonstrates that major fault systems in the Himalaya accommodate self-organized patterns of deformation that persist for tens of millions of years.

Professor Leigh Royden has spent the past year examining the dynamics of subduction zones, including the effects of slab density and mantle viscosity on the geometry and subduction rate of the lithosphere. It appears that subduction zone behavior is very sensitive to density variations in the subducting lithosphere, even on very short length and time scales (100 km and several million years). This research offers new insights into the evolution of small subduction systems in the Mediterranean region, such as in the Aegean.

Professors John Southard and John Grotzinger, in collaboration with researchers at Chevron, are making large-scale laboratory experiments on the depositional structure of submarine fans built by turbidity currents, which are currently the major targets for offshore petroleum exploration.

Professor Kelin Whipple initiated a major new direction in his work in tectonic geomorphology, the study of glacial erosion, climate change, and long-term interactions between climate and tectonics. Along with several other publications on bedrock channel erosion, a paper redefining scientific approaches to this important problem has been completed.

Professor Brian Evans and colleagues are studying melt migration in oceanic rocks by deforming partially molten peridotites in a deformation apparatus utilizing a gas confining medium. The experiments measure variations of the rate of melt extraction caused by variations in stresses, lithostatic and melt pressure, and temperature, and simulate processes occurring underneath the oceanic ridges.

Professors Bradford Hager and Robert van der Hilst, in collaboration with sabbatical visitor Professor Louise Kellogg, of UC Davis, have published a new paradigm for layering of the convective circulation in Earth's interior, reconciling heretofore seemingly contradictory observations from seismology, geochemistry, heat flow, and other geophysical observations. Using computer simulations, they demonstrated that an abyssal layer of material, intrinsically about 5 percent more dense than the overlying mantle, and enriched in radioactive heat producing elements is dynamically stable.

Professor Thomas Herring, with research scientists Robert King and Simon McClusky, has been applying the Global Positioning System (GPS) to global and regional scale deformation problems, and to remote sensing of atmospheric water vapor. With his students, Professor Herring has also been working on aircraft and spacecraft laser altimetry for topographic profiling.

Professor Thomas Jordan and his collaborators have been using data from a large deployment of temporary, broad-band seismometers in southern Africa to study the structure of the ancient Kaapvaal craton. They have also been using deep gold mines in the Witwatersrand basin of South Africa as "natural laboratories" for investigating the physics of rock deformation and failure.

Professor F. Dale Morgan and his students, using a variety of electromagnetic techniques, have imaged underground contaminant plumes on Cape Cod. They have also developed and tested novel methods for identifying and imaging underground caverns.

Professor Daniel Rothman and his students have combined analytic theory, numerical simulations, and observations made from digital elevation maps to explain many of the scaling laws obeyed by natural river networks.

Professor Nafi Toksöz and his students developed a method for measuring and analyzing the electrical signals generated by fluid motion in porous rocks due to a passing seismic wave. Their results have significant application in the oil and gas industry for remotely estimating reservoir fluid flow properties. Professor Toksöz, together with Research Associate Roger Turpening, developed and tested a method for imaging subsurface structures with seismic waves using a random distribution of surface receivers.

Senior Research Scientist Peter Molnar and MIT graduate student Clint Conrad developed a scaling law for growth rates of convective instability that takes into account the dependence of viscosity on depth and therefore on temperature. This "available buoyancy," the integrated ratio of density to viscosity over depth, allows us to estimate how fast the instability at the base of mechanically thickened lithosphere (beneath a mountain range) would grow and therefore to bound the amount of lithosphere that would be removed by such a process.

Principal Research Scientist Robert Reilinger, Principal Research Scientist Robert King, Research Scientist Simon McClusky, and Professor Nafi Toksöz are coordinating an international project to use the Global Positioning System to map crustal deformation throughout the Mediterranean region, providing new constraints on lithospheric rheology and dynamics in this plate collision zone. Reilinger, King, and McClusky are also using new GPS measurements in southern California and northern Baja, Mexico to map deformation along the San Andreas Fault system to quantify fault slip rates for earthquake hazard studies.

Professor Robert van der Hilst and his collaborators demonstrated conclusively that convection in the Earth's mantle involves tectonic plates sinking from Earth's surface deep into the lower mantle and later found evidence for compositional stratification at larger depth than hitherto thought. In collaboration with Professor Hager, they demonstrated the feasibility of a dense, compositionally distinct layer in the bottom 1000 km of the mantle, which may satisfy both the geophysical and the geochemical constraints.

Professor Richard Binzel has utilized ground-based telescope to investigate the compositional properties of asteroids passing near the Earth, and has discovered a size dependence for these properties. Smaller objects show more distinct mineral absorption bands in their spectra that may be related to the fresh exposure of their surfaces to the space environment.

Professor James Elliot and his colleagues analyzed stellar occultation data recorded with the Hubble Space Telescope and found that the troposphere of Neptune's largest moon, Triton, is much deeper than expected–most likely due to turbulence created by the moon's strong winds.

Professor Jack Wisdom has been investigating the non-linear dynamics of coupled core-mantle systems subject to astronomical forcing. He has found that the offset of the core angular momentum from the mantle angular momentum can behave chaotically as Earth and Venus tidally evolve through resonances between the core precession period and the orbital period. He is writing a book on classical mechanics with Professor Gerald Sussman in EECS which presents mechanics from a modern non-linear dynamics perspective, and make extensive use of simulation for active exploration of non-linear phenomena in mechanics.

Professor Maria Zuber and colleagues at the Goddard Space Flight Center and other universities used their laser altimeter on the Mars Global Surveyor spacecraft to produce the first high-resolution global map of the topography of Mars. From the topographic dataset they provided the first reliable estimate of the present-day surface water inventory on the planet, identified pathways and sinks of water earlier in Mars' history, and quantified contributions of impact, tectonism and volcanism in shaping the planet during the course of its evolution.

Professor Edward Boyle and his research group have developed a new technique for the study of biologically-essential iron in the ocean; it turns out that only half of the iron in seawater is truly dissolved; the other half exists as extremely small colloids (0.02—0.1 microns). He has also demonstrated that the deep ocean circulation is linked to changes in surface climate on decadal-centennial time scales.

Professor Edmund Chang examined the structure and evolution of wave packets in the upper troposphere using observational and modeling studies, and discovered how wave energy evolved in these wave packets as well as how they are maintained.

Professor John Edmond continues to examine the oceanic and atmospheric chemistry of Iodine-129, which has a half-life of 16 million years. A new field area in Western Sichuan and Eastern Tibet has opened up for his studies of river chemistry while an old area in Eastern Siberia has been closed down for political reasons.

Professor Kerry Emanuel's major accomplishment this past year has been to show that hurricane intensity is in fact predictable, many days in advance, if the track is reasonably well forecast. Current hurricane intensity prediction schemes show little or no skill, even at short lead times.

Professor Glenn Flierl and his students are conducting research on the impacts of oceanic eddies upon the distribution of tracers and on the biology of the sea, including both transport and alterations in the reaction terms. We are also examining the dynamics of zooplankton and right whales in the near-shore region off Provincetown and have shown that the patchiness of the zooplankton, created by both the physics and swarming processes, dramatically alters the feeding rates of the whales.

Professor Richard Lindzen and his collaborators are continuing their work on the use of satellite data to directly measure climate sensitivity, taking advantage of specific information concerning the physics of clouds and water vapor in order to greatly increase the signal to noise ratio; preliminary results appear dramatic. Among other activities, Lindzen and collaborators have also developed a new explanation for the tropical intra-seasonal oscillation (sometimes referred to as the Madden-Julian Oscillation).

Professor Paola Malanotte-Rizzoli and collaborators have focussed their most recent research on the heat, tracer and mass transport exchanges between the subtropics and the tropics in the global ocean. The major results show that in the Pacific Ocean the subtropical/tropical exchanges are responsible for the symmetric meridional heat transport, directed poleward in both hemispheres, while in the Atlantic Ocean the interaction with the Meridional Overturning Circulation makes the meridional heat transport to be northward everywhere.

Professor John Marshall and his group have been studying the interaction of the North Atlantic Oscillation with ocean circulation and the possible role of the ocean in modulating the strength of the atmospheric jet-stream on decadal timescales. This is providing a scientific focus for the global ocean and atmospheric models his group is developing in the Center for Global Change Science's Climate Modeling Initiative.

Institute Professor Mario Molina and his research group have continued the laboratory studies of the chemical processes of atmospheric importance. They have developed a new optical microscopy technique to study liquid-solid phase transitions in aerosol particles. Their results have led to significant improvements in the understanding of stratospheric ozone chemistry and the formation of cirrus clouds in the upper troposphere and lower stratosphere. In addition, they have launched a new multidisciplinary, integrated assessment project on air pollution in mega-cities, using Mexico City as a case study, and aimed at improving the environmental decision-making process through education and the better use of scientific, technical and socioeconomic understanding.

Professor Reginald Newell was Mission Meteorologist as part of a NASA experiment to measure atmospheric trace gases in the South Pacific to study the influence of anthropogenic urban pollution and biomass burning on atmospheric chemistry, particularly the ozone budget.

Professor Alan Plumb has been investigating the use of tracer correlation diagrams to identify loss processes in the Arctic stratosphere; observed "losses" of ozone and reactive nitrogen can actually occur through mixing, and many published studies of Arctic ozone loss and denitrification are seriously flawed. With graduate student C. Juno Hsu he found, and modeled, hitherto unreported unsteady behavior of the Asian monsoon anticyclone in the upper troposphere; the anticyclone becomes unstable and, about once every 3 weeks, sheds an anticyclonic eddy westwards.

Professor Ronald Prinn and his collaborators have used their coupled model of economic development, biogeochemistry, climate dynamics, and ecosystems to evaluate the scientific and economic implications of the Kyoto Protocal for restricting greenhouse gas emissions. They show the Protocol by itself will have little influence on climate, and demonstrate the limitations of schemes to rank the various greenhouse gases.

Professor Stone, along with colleagues from the MIT Joint Program on the Science and Policy of Global Change and from Oxford University, has applied climate change detection techniques for the first time to quantify objectively the uncertainties in climate models and their projections of climate change. If one requires a 95 percent confidence in the range of projections, their results show a much greater uncertainty in the projections (by more than a factor of two) than the range commonly quoted by the Intergovernmental Panel on Climate Change and others.

Professor Carl Wunsch and his collaborators have focussed on estimating the time varying ocean circulation by combining global general circulation models and the recently available global data sets. Their results show that it is possible to solve this enormous optimization problem, and the solution displays rather startling variability in the circulation, particularly at high latitudes.

Principal Research Scientist Detlef Stammer developed, in collaboration with Professor Carl Wunsch, a model which is capable of predicting and correcting fast barotropic motions in altimetric sea surface height observations which other wise would be a serious alias. In collaboration with Prof. Jochem Marotzke he developed a methodology by which the MIT adjoint Ocean Circulation Model can be used to study mechanisms responsible for changes in the meridional heat transport in the ocean and associated climate changes.

More information about this department can be found on the World Wide Web at the following URL: http://www-eaps.mit.edu/.

Ronald G. Prinn

MIT Reports to the President 1998-99