Dr. Hirschberg,

Thanks for your question. The major advance is theoretical in nature. One of the goals of oceanography is to map-out the pathways and speeds of the ocean’s circulation (surprisingly little is known for sure). Previous studies have inferred aspects of the circulation using the time-lagged correlation of oceanic time series data (e.g. Sutton and Allen, Nature, 1997, who analyze sea surface temperatures propagating across the Atlantic and infer a mean current speed of 1.7 cm/s in the Gulf Stream). However these studies invite skepticism because they lack a theoretical framework for connecting correlation functions to fluid dynamics equations (correlation doesn’t imply causation). Our major advance has been to provide that framework. This was accomplished using the Green’s function solution of the fluid transport equations. Also, in developing the theory, we realized that a properly done time-lagged correlation could contain more information about the physical transport process than previous thought. We’re now applying the theory to reveal new aspects of the circulation in the North Atlantic.

Dr. Cowles,

Great question.  My advisor and his colleagues (as far as we know) were the first to use Green’s functions to interpret large scale oceanic circulation (e.g. Haine and Hall, Generalized Transport, 2002).  Its has also been applied to transport in lakes, ground water flows, and the atmosphere (see publications by Darryn Waugh).

Many of the applications above interpret the spread of passive tracers (such as CFC molecules) in the flow.  My work builds on and expands this work by including the correlation of propagating temperature and salinity anomalies as a source of oceanic data which can be interpreted by the Green’s function framework.

Dr. Bassiouni,

I hope so!  An interesting and related application is the Green’s function retrieval in the field of seismology.  Here they characterize waves propagating through the Earth’s crust by correlating small fluctuations in seismic activity (Sneider, Retrieving the Green’s function, 2006).   In a wider sense, the theory of relating correlation functions to Green’s functions can be applied to any system of stochastically forced linear partial differential equations.

If global warming alters the overturning circulation in a significant way, we could see drastic changes in temperature and precipitation patterns in Europe.  This is because the overturning circulation drives the Gulf stream which heats Europe’s atmosphere.  The main practical implication is the impact on crop production.  However that in turn could lead to more serious economic and political consequences.

Thanks Adam! Many of the animations were produced by the data visualization studio at the NASA Goddard Space Flight facility.

Thanks Tanya! Sorry I didn’t include the ducks :)

Me too! Thank you.

Edinah, good idea. A professor in my department also suggested atmospheric applications. Something I’m excited to look into!

Thanks Ashley! I was going for multiple meanings of a “climate of curiosity.”