Annual cycles of sea level and sea surface temperature in the western Mediterranean Sea

Abstract

[1] In the western Mediterranean Sea, sea level variations are the result of seasonal steric effect, atmospheric forcing and mesoscale circulation activity, particularly in the Alboran and Algerian basins, as well as water mass budget variations including flux variations through the Straits of Gibraltar and Sicily. However, the partition of the magnitude of the sea level variations associated with these different components remains a challenging problem. A better determination of the steric effect component will allow a better knowledge of the other annual components. The aim of this study is to improve the estimation and understanding of the annual sea level variations in the different basins of the western Mediterranean Sea, using sea level anomalies (SLA) derived from TOPEX/ POSEIDON and ERS-1/2 altimeters and sea surface temperatures (SST) derived from NOAA/AVHRR infrared imagery, obtained between 1992 and 1998. The first mode of empirical orthogonal function (EOF) analysis on SLA is annual and represents 63% of the total variance. The first mode of EOF analysis on SST anomalies is also annual and represents 98% of the total variance. The lag between the annual variations of SLA and SST is about 40 days. From these EOF results and a parameterisation of the mixed layer, the seasonal dynamic height and the steric effect are estimated and removed from the SLA. The remaining signal is used to examine the annual cycles of the sea level due to water mass budget variations, mesoscale oceanic variability and atmospheric forcing.

Analysis of a 44-year hindcast for the Mediterranean Sea: comparison with altimetry and in situ observations

“…The computed steric height of the model shows an annual cycle amplitude of ~5 cm, and the full SSH signal as diagnosed by the model of ~10 cm. These values coincide with the altimetry data and are confirmed by Bouzinac et al (2003) and Larnicol et al (1995).…”

SLA–chlorophyll-a variability and covariability in the Algero-Provençal Basin (1997–2007) through combined use of EOF and wavelet analysis of satellite data

“…The variability of the SLA in the area was previously investigated by some other authors (Vignudelli 1997;Bouzinac et al 1998Bouzinac et al , 2003Cipollini et al 2008). In particular, Bouzinac et al (1998Bouzinac et al ( , 2003 used an EOF approach to analyze SLA, similar to that used in this paper.…”

“…The loadings of EOF-1 are in phase in the whole domain, meaning that for this mode of variability, there are variations of the same sign. The homogeneous (in phase) seasonal variation of SLA over the domain is mainly due to the steric effect, quantified for the whole western Mediterranean by Bouzinac et al (2003). The associated expansions coefficients (PC-1, bottom panel of the figure) depict a typical annual signal with maxima in autumn and minima in spring, accordingly with Bouzinac et al (2003).…”

“…The homogeneous (in phase) seasonal variation of SLA over the domain is mainly due to the steric effect, quantified for the whole western Mediterranean by Bouzinac et al (2003). The associated expansions coefficients (PC-1, bottom panel of the figure) depict a typical annual signal with maxima in autumn and minima in spring, accordingly with Bouzinac et al (2003). Differences between variances explained by EOF-1 observed in the present study (76%) and in Bouzinac et al (2003, 63%) can be attributed to the different length of the time series, to the different periods and areas covered by the data, and probably to slight differences in the data pre-/post-processing.…”

“…1), and for this reason, its hydrodynamics was broadly investigated in the past (e.g., Vignudelli 1997;Levy et al 1999;Millot 1999;Levy et al 2000;Bouzinac et al 2003;IsernFontanet et al 2004). It is divided in two parts, southern and northern, by the North Balearic Front.…”