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Climate Variability & Change

The Earth environment is changing in unprecedented ways; the surface air temperature is increasing rapidly, glaciers and ice sheets are melting faster than expected, and sea level is rising at an alarming rate. Together these changes may be detrimental to our environment; at the same time, they may present opportunities for new insights and an improved understanding of the Earth System. The goal of our proposed work is to identify and account for sea level rise in terms of steric and non-steric sources and relate these to climate change. Satellite altimeters have observed a robust sea level rise over the last decade of nearly 3 mm per year; comparisons with expansion of sea water based on in situ temperature and salinity data suggest that the contribution of water previously stored on land to the observed sea level rise is substantial and increasing. Still, uncertainties in the collection and processing of data regarding water mass transfers within the Earth system have limited our ability to adequately investigate the sources of the observed sea level rise. Our work has several thrusts. We will examine the interactions among the various Earth subsystems, the processes involved, and their implications for the response of the total Earth system to a changing climate. We will consider melting glaciers and ice sheets, warming oceans and increasing sea level rise, warming surface air temperature, atmospheric loading effects and the changing hydrological cycle; the guiding question will be to find out how these changes affect the Earth and what is expected in the future. In addition to the fundamental-science questions, we will consider how these unprecedented changes are affecting our standard definitions and terms of reference, such as the terrestrial reference frame (TRF); they may present challenges in maintaining stable reference frames and definitions that can adequately represent the Earth as a system without introducing systematic errors. Another focus of this proposal is the use of new and innovative statistical techniques to more fully examine the sources of sea level rise and their relationship to measured effects. Separation of steric and non-steric sea level rise from the total sea level record can be accomplished using Singular Spectrum Analysis (SSA) and Multi-Chanel SSA (M-SSA), applied jointly to complementary geophysical data sets. SSA isolates modes of regular variation in the individual series, including nonlinear trends and oscillatory modes, while M-SSA helps identify common modes variability among times series. We will use M-SSA to analyze the common variability of the altimetric sea surface height field together with GRACE gravity anomalies, in order to better separate the non-steric part from the total sea level rise and understand its sources of variability. Likewise, we will use M-SSA to examine and compare sea surface heights with sea surface temperatures (SSTs) and ocean heat content distributions, in order to help us separate the steric contribution. Comparison of SSTs with the steric sea level will allow us to study the differences between near-surface and integrated ocean heat variations; such a comparison could also provide insights into the extent to which the longer SST records may help extend the ocean heat content series back in time.

Project PI: Jean Dickey/Jet Propulsion Laboratory / California Institute of Technology

Jet Propulsion Laboratory M/S 238-600 4800 Oak Grove Dr. Pasadena, CA 91109

Phone: (818) 354-3235

Fax: (818) 393-4965

Email: jean.o.dickey jpl.nasa.gov

http://scienceandtechnology.jpl.nasa.gov/people/j_dickey/

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Started: Sep 29, 2010

Last Activity: Jan 04, 2011

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