Relation between sea level and bottom pressure and the vertical dependence of oceanic variability

Abstract

[1] The relation between large-scale sea level and bottom pressure variability is studied using long (50-yr) simulations of a general circulation model under realistic forcing. Admittance and coherence analyses are used to characterize the bottom pressure and sea level relationship as a function of period, horizontal spatial scale, and location. At the model grid scale (1°), bottom pressure is found to be essentially equivalent to sea level at periods <30 days, except in the tropics. This equivalence still holds for longer periods ($100 days), but only at high latitudes (>60°) and in shallow depths (<200 m). Elsewhere, bottom pressure and sea level fields can differ significantly. Results indicate an increase of the importance of baroclinic signals with decreasing latitude and spatial scale, with significant baroclinic signals at intra-seasonal and longer periods present in many subtropical and mid-latitude regions. Variability is clearly baroclinic at inter-annual periods, regardless of location and spatial scale. Results have broad implications for the interpretation and processing of both satellite altimetry and gravity data and for their assimilation into numerical models. Citation: Vinogradova, N. T., R. M.Ponte, and D. Stammer (2007), Relation between sea level and bottom pressure and the vertical dependence of oceanic variability, Geophys. Res. Lett., 34, L03608,

Deciphering the ocean bottom pressure variation in the Logatchev hydrothermal field at the eastern flank of the Mid-Atlantic Ridge

“…Send, Scripps Institution of Oceanography, La Jolla, United States, Figure 13) likewise reported by Bryden et al [2009] from the oceanographic RAPID array more than 1000 km further north in the Atlantic Ocean at 26°N. Also our results support the conclusion from the modeling of Vinogradova et al [2007] who found the sea level and bottom pressure to be increasingly uncorrelated toward lower latitudes.…”

Arctic Ocean Circulation Patterns Revealed by GRACE

“…This work is in a sense an observational perspective of the work of Vinogradova et al (2007) and Bingham and Hughes (2008). Based on the results from this paper, at the time scales and the places where the Arctic Ocean is barotropic (i.e., predominantly on the shelves), GRACE OBP may be used to identify SSH variations.…”

“…The dominance of the barotropic contribution over the baroclinic contribution to OBP variations depends on depth, latitude, time scale, and stratification (Gill and Niiler 1973;Vinogradova et al 2007;Bingham and Hughes 2008). Modeling studies indicate that at high latitudes (Vinogradova et al 2007) and at the Arctic Ocean in particular , and at annual and shorter time scales, the circulation is predominantly barotropic, whereas at interannual and longer time scales, circulation adjusts baroclinically.…”

“…Modeling studies indicate that at high latitudes (Vinogradova et al 2007) and at the Arctic Ocean in particular , and at annual and shorter time scales, the circulation is predominantly barotropic, whereas at interannual and longer time scales, circulation adjusts baroclinically. Only in the shallow regions of the Arctic shelves (e.g., ,200 m) do the SSH fluctuations in the model of Bingham and Hughes (2008) remain coherent with OBP fluctuations at longer than seasonal time scales.…”

A global comparison of Argo and satellite altimetry observations

“…Values are of the order of 0.8 or higher in the tropical regions and decrease to 0.6 north of 40 • N and to 0.3-0.4 south of 40 • S. The low values of the regression coefficients at high latitudes are due to strong barotropic signal and deep baroclinic signals (Vinogradova et al, 2007). This leads to an underestimation of the steric part of the sea level by DHA calculated using a 1000 m depth reference level (Fig.…”