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Ocean Surface Topography from Space
SCIENCE
Using altimetry to monitor the ocean's response to a changing climate


Author:

Rory J. Bingham - (University of Bristol)

Co-Investigator(s):
  Philip Moore (Newcastle University)


Abstract:
Image for Using altimetry to monitor the ocean's response to a changing climate
The mean circulation of the North Atlantic as revealed by satellite altimetry and satellite gravimetry. (a) The mean dynamic topography for the period 1993-1999 found by differencing the CLS01 mean sea surface and the 3rd generation of the timewise GOCE geoid height model. (b) The associated mean geostrophic surface currents.
Understanding how the ocean will respond to a changing climate is surely the most important challenge facing oceanographers today. Two of the most significant issues are the determination of long-term changes in global and regional sea-level, and understanding the mechanisms by which the ocean redistributes the Sun's energy thereby regulating the Earth's climate. As one of the UK's leading groups applying geodetic and other satellite observations to study geophysical processes, and with extensive experience and expertise in sea-level and geodetic oceanography, Newcastle University is actively engaged in addressing these questions. High quality altimetry data is a key component of our research, and in this proposal we describe how we intend to exploit this data to its fullest potential in meeting the oceanographic challenges posed by a changing climate. Given the wide variety of projects using altimetry data with which Newcastle University is engaged we provide self-contained descriptions of each activity grouped under the themes of 'Dynamic Topography', 'Long-term Changes in Sea-level', and 'Ocean Dynamics'.
Dynamic topography: An important question concerns the determination of the ocean currents, which by transporting heat, regulate the Earth's climate. ESA's Gravity and Ocean Circulation Explorer (GOCE) mission is for the first time providing sufficiently accurate measurements of the Earth's gravity field to allow the absolute values and positions of these currents to be accurately determined. To this end Newcastle University has been engaged in a number of international projects in support of the GOCE mission, including the development of methods for determining the ocean's mean dynamic topography (MDT), the development of the GOCE User Toolbox (GUT) that facilitates the use of altimetric and geodetic data by the wider oceanographic community, and the development of MDT products and strategies that will allow this data to be assimilated into ocean models. As an essential part of this we are also working to understand the physical significance of the scales represented by the MDT.
Long-term Changes in Sea-level: Working closely with the UK's National Oceanography Centre (NOC), which hosts the Permanent Service for Mean Sea Level (PSMSL), Newcastle University has long been involved in the complementary activities of calibration and validation of altimetry data (clearly also important for all uses of altimetry data) and the quantification of long-term changes in global mean sea level, both of which combine in-situ and satellite measurements of sea-level. Newcastle University will continue to maintain and extend this important verification dataset, and work with colleagues at other institutes to develop robust and semi-automated calibration methods, while making the data available to the altimetry community for calibration purposes. Newcastle University will continue to refine estimates of global mean sea-level rise, and work with colleagues at the NOC and the UK Met Office to understand the causes of low-frequency sea-level variability, both global and regional, seen in climate models, as well as developing fingerprinting methods to constrain the ocean mass flux budget.
Ocean Dynamics: Finally, we are engaged in numerous investigations of ocean dynamics where altimetry is an important dataset. We describe two of these: the use of altimetry in understanding and monitoring the North Atlantic meridional overturning circulation, and calculating the work done on the ocean by the wind.



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