Intellectual Merit: Images of monthly averaged sea surface temperature (SST) front probability show zonal bands at mid-latitudes in all major ocean basins with a meridional separation of approximately 400 km. These bands are visually correlated with ridges of sea surface height (SSH) anomaly in the eastern South Pacific and with bathymetry. Furthermore, they are stable over many years. The dynamics giving rise to these features are not understood at present. Current hypotheses range from zonal jets resulting from baroclinic instability and geostrophic turbulence to preferred eddy pathways determined by mean flows or eddy interactions. The specific objectives of this project are: to quantify the relationship between persistent bands of frontal probability and persistent ridges in mean SSH fields; to determine the origin and maintenance of quasi-zonal bands of SST front probability; to characterize the inter-annual variability of the location of bands in the frontal probability fields; and, to analyze the impact of bottom topography on bands of frontal probability. The ubiquity of the observed zonal structures, their zonal extent, their persistence in time and the uniform meridional scale in all basins and all seasons suggests that they result from fundamental dynamic processes in the ocean. The tight correspondence between features in these structures and deep bathymetry suggests that they are involved with processes that extend well below the main thermocline. As such, understanding their origin will likely contribute to a better understanding of the general circulation of the ocean.
Broader Impacts: In the course of the project, frontal data sets from a variety of satellite-derived SST fields extending from 1981 to present at a variety of spatial and temporal resolutions will be made available to the oceanographic community. Preliminary work suggests an ocean to atmosphere impact of the SST anomalies associated with frontal bands. Specifically, atmospheric water vapor is higher over these anomalies than the background. There is also a potential connection with geology in that the features associated with the bands are persistent in time - possibly over very long times with impacts on deposition on and scouring of the sea floor. Understanding the dynamics and persistence of the zonal striations will also be important to understanding ocean transports over long timescales affecting climate and thereby benefit our understanding of the ocean role in Earth's climate. This would also motivate efforts for parameterizing these ocean processes for representation in coarse coupled global climate models. The band detection algorithms and the analyses therein, as developed in this proposal, provide important scale information that can be useful in the design and maintenance of global ocean observing systems. This project will also support the training of one graduate student.
