High-wavenumber variability in the California Current from new altimeters
Event: 2016 Ocean Surface Topography Science Team Meeting
Session: Science II: From large-scale oceanography to coastal and shelf processes
Presentation type: Type Poster
Coastal regions, such as the California Current, are marked by comparatively small eddy features with diameters less than about 50-100 km that are difficult to resolve with conventional altimetry. Results from underway shipboard Acoustic Doppler Current Profiler data and from a 1/48 degree resolution version of the MITgcm indicate that for scales smaller than about 80 km, wavenumber spectra of sea surface height are likely to be dominated by internal wave related processes, with relatively shallow (k<sup>-2</sup>) spectral slopes that could be difficult to distinguish from noise. We evaluate the prospects of using retracked AltiKa altimetry and/or Sentinel-3 SAR mode altimetry to assess high-wavenumber structures within the California Current region. The Ka-band altimeter has a nominal footprint of about 5 km and should be able to resolve smaller features than the Ku-band Jason altimeters, though retracking is required to achieve small-scale resolution, and the spectral hump is not easily eliminated. The SAR mode altimeter should in principle resolve scales as small as 1 to 2 km, albeit with background noise that may exceed that of AltiKa. Because altimeter noise and internal wave signals are difficult to distinguish at high wavenumbers, some uncertainty remains regarding the sources of spectral slopes at high wavenumbers. Comparisons with in situ data and model output can help in distinguishing measurement noise and high-wavenumber characteristics of the ocean surface.