Climate
Research at the Institute for Geophysics
Themes
Driving Climate Science
Climate science is a rapidly advancing field and is being thrust into
the public arena by the need of policy makers to make informed decisions about
humanity’s stewardship of the natural environment. Although the physics
governing the climate system is relatively straightforward, it is the countless
ways that different components of the climate system interact at all spatial and
timescales that make climate phenomena difficult to understand. Even the best
climate models that the world has produced up to this point provide a scattered
perspective on what will happen when greenhouse gases double as is expected to
occur within the next 100 years. The main goal of climate science today is to
understand the checks and balances that maintain modern climate and to predict
how these checks and balances may be affected by anthropogenic forcings. One of
the fundamental limitations to characterizing nature’s balances is the limited
applicability of the modern instrumental record to provide the ‘long-term’
perspective that is necessary to establish 1) what natural variability is and 2)
the different ways components of the climate system interact.
The Institute for Geophysics is strong in the more mathematical and
computationally intense aspects of the geosciences and geophysics in particular.
The Institute has a distinguished history in the collection of geophysical data
and its subsequent interpretation using tools of ‘data inversion’ that
permits one to find connections between data, theory, and models.
The Institute also has a unique perspective on climate through its close
association with the gathering and interpretation of paleoclimate proxy records.
These data are essential to climate science’s need for a longer baseline of
natural variability and the observations of how each of the components of the
climate system (atmosphere, ocean, ice sheets, and land surface) responds to
known forcings in the past.
The Institute can serve a unique role within the
climate science community by focusing on problems that require an advanced level
of scrutiny of the data and/or models that are used to understand the sources of
natural variability on seasonal to million-year time scales, especially
variability that results from the interaction of the different components of the
climate system including the atmosphere, ocean, ice sheets, land surface, and
the solid earth. Each example of a strategic research theme draws upon specific
disciplinary strengths in atmosphere and ocean dynamics, ice sheet dynamics,
geologic records of climate or airborne geophysical surveys of ice sheets and
their underlying bedrock.
Resources
The computing resources that are available for climate research
include multiple Linux-based PC and workstation clusters. Computer clusters in
general are well suited for ‘data-inversion’ and uncertainty estimation
through their ability to complete of suites of model experiments simultaneously.
Two 16-processor AMD clusters and one 16-processor Alpha cluster are maintained
at the Institute. The Institute also owns ~180-processors of the
Intel-Xeon clusters maintained at the Texas Advanced Computer Center. The clusters use Myrinet for fast cross-cluster communication.
The airborne geophysics group at the Institute, in its focus on ice
sheet–Lithosphere interactions, has built an unparalleled capacity to study
glacier and ice sheet processes in concert with investigations of lithospheric
processes at sub-continental to outcrop scales. The airborne geophysical
platform package includes a suite of ice-penetrating radar sounders, a laser
altimeter, a gravimeter, and a magnetometer that are tightly integrated with
each other as well as with the avionics and power systems of a deHavilland
“Twin Otter” aircraft. This instrumentation package also includes aircraft
and ground-based GPS receivers to support kinematic differential positioning
using carrier-phase observations. Taken together, this system is uniquely
capable of simultaneously measuring the precise surface elevations and ice
thicknesses critical for glacier and ice sheet studies, as well as the potential
fields necessary for inferring sub-ice geology.
Strategic Research Themes
Quantifying Climate Model Prediction
Uncertainties
The wider climate community is actively trying to address why the world’s best climate models give divergent predictions of the amount of warming that will occur when CO2 is doubled. Although thousands of parameters exist within a typical climate model, it is likely that a few parameters account for these differences. A research program has begun at the Institute for Geophysics to prototype new efficient methods to quantify climate model prediction uncertainty stemming from the combined influence of multiple, non-linearly related parameters. Our vision is to lead the nation’s effort to develop an automated system to quantify climate model parameter uncertainties capable of combining information from all observational platforms that are monitoring key aspects of the climate system. This will be followed by a research effort aimed at using paleoclimate proxy data to constrain climate model prediction uncertainties of future climate.
Climate Predictability and
the Role of the Upper Ocean
The
upper ocean is crucial for predicting seasonal to inter-annual climate
variations since this is where the ocean communicates directly with the
atmosphere. New opportunities exist to observe the upper ocean via satellite
based sensors maintained by the University of Texas
Center for Space Research. A
research program is underway to explore novel ways to use these satellite-based
measurements to tease apart the various processes that control sea surface
temperature variations.
Coral Records of Climate
Variability in the Tropical Pacific
The largest knownsource
of natural climate variability originates from ocean-atmosphere interactions
within the tropical Pacific. This region is thought to be a critical participant
in major climate reorganization events observed in other paleoclimate proxy
records although there currently does not exist sufficient data to determine
what its role may have been. An opportunity exists for the Institute to take the
lead in extracting precise paleoclimate records from living and fossil corals
within the tropics and to develop new theories about how the tropics is tied to
the rest of the climate system.
Ice Sheet Sheets and Abrupt
Climate Change
Abrupt
climate changes were defined first in annually layered Greenland ice cores and
subsequently recognized in other climate records.
It is commonly believed that abrupt climate transitions observed in the
Greenland ice cores are related to major reorganizations of the meridional
overturning circulation (MOC) within the Atlantic (although we still do not know
how these changes explain the extent of what is observed globally). Many models
predict that the MOC will weaken in the future due to an increase in atmospheric
moisture convergence to the higher northern latitudes. Models also indicate that
a decrease of the MOC strength reduces the circulation’s stability and thereby
increases the chance it could collapse completely. An open question is what may
be the role, especially the timing, of the melting Greenland ice sheet to the
high latitude freshwater balance. The Institute for Geophysics is in a unique
position to collect observations of the internal layers of Greenland ice using
airborne geophysical surveys, something that is currently being done in
Antarctica. The structure of these internal layers is indicative of ice sheet
behavior and climate forcing through time. These observations would provide
perhaps the best perspective on the history of Greenland ice sheet dynamics and
the potential for the ice sheet to undergo sudden changes to its mass balance
and supply of freshwater to the North Atlantic.
Airborne Studies of Ice
Sheet – Lithosphere Interactions
The geothermal heat and sediment characteristics at the base of an ice sheet to a great extent determine the size, flow, and overall fate of ice sheets and sea level through time. These conditions are often not independent of the ice but are related to the existence of former glaciers or ice sheets to cause the deformation, exhumation, and depression or uplift of the Lithosphere. Although much of these interactions occur over tens of millennia to millions of years, there are geologic records that indicate it is possible for vast segments of an ice sheet to collapse within a few hundred years. The airborne geophysics group at the Institute for Geophysics is the world’s leader in the use of multiple sensors to observe the internal structure of ice sheets and the upper Lithosphere. The vision for this group is to provide the critical observations that would be necessary to develop an understanding of how ice sheets interact with the Lithosphere to cause observed long-term climate variability. Outstanding questions include; the origin of the East Antarctic ice sheet, its contribution to the Cenozoic transition from a “greenhouse” to an “icehouse” world, and how it may respond to a climate warming; the cause of observed thinning of the portion of the West Antarctic ice sheet bordering the Amundsen Sea and of abrupt shifts in the flow of West Antarctica ice streams; the relationship between the basal boundary conditions controlling the evolution of the Greenland ice sheet and Greenland’s traversal by the Iceland hotspot; and, the role of glacial processes in the rapid uplift of Southeast Alaska and the effect of the uplift on the nucleation of the Cordilleran ice sheet.