Quantifying mesoscale variability in ocean transient tracer fields
Article first published online: 20 SEP 2012
Copyright 2001 by the American Geophysical Union.
Journal of Geophysical Research: Oceans (1978–2012)
Volume 106, Issue C7, pages 13861–13878, 15 July 2001
How to Cite
2001), Quantifying mesoscale variability in ocean transient tracer fields, J. Geophys. Res., 106(C7), 13861–13878, doi:10.1029/1999JC000036., and (
- Issue published online: 20 SEP 2012
- Article first published online: 20 SEP 2012
- Manuscript Accepted: 7 APR 2000
- Manuscript Received: 10 AUG 1999
A powerful way to test the realism of ocean general circulation models is to systematically compare observations of passive tracer concentration with model predictions. The general circulation models used in this way cannot resolve a full range of vigorous mesoscale activity (on length scales between 10–100 km). In the real ocean, however, this activity causes important variability in tracer fields. Thus, in order to rationally compare tracer observations with model predictions these unresolved fluctuations (the model variability error) must be estimated. We have analyzed this variability using an eddy-resolving reduced-gravity model in a simple midlatitude double-gyre configuration. We find that the wave number spectrum of tracer variance is only weakly sensitive to the distribution of (large scale slowly varying) tracer sources and sinks. This suggests that a universal passive tracer spectrum may exist in the ocean. We estimate the spectral shape using high-resolution measurements of potential temperature on an isopycnal in the upper northeast Atlantic Ocean, finding a slope near k−1.7 between 10 and 500 km. The typical magnitude of the variance is estimated by comparing tracer simulations using different resolutions. For CFC- and tritium-type transient tracers the peak magnitude of the model variability saturation error may reach 0.20 for scales shorter than 100 km. This is of the same order as the time mean saturation itself and well over an order of magnitude greater than the instrumental uncertainty.