Signature of the coastal circulation variability in altimetric data in the southern Bay of Biscay during winter and fall 2004

Abstract

The upper circulation in the southern Bay of Biscay is analysed over winter and fall 2004 using a coastal altimetric dataset, moorings, sea surface temperature (SST) observations and a regional simulation from the SYMPHONIE model. The aim is to determine whether altimetric data can detect occurrences of a slope current (the Iberian Poleward Current, IPC). We first analyse in situ and SST data. The results show pulses of a warm surface poleward flow (IPC) limited to the westernmost part of the northern Spanish coast. Along-track TOPEX/Poseidon and Jason-1 data are analysed over three 'events' (Jan., Feb., and Oct. 2004). Altimetric data can depict the main pulses. They provide some information on their spatial variability but the present in situ dataset is not dense enough to assess this information. Local inconsistencies between neighbouring tracks may be related to uncertainties in altimetric corrections. The simulated fields are consistent with the in situ observations. They allow us to better understand the IPC subsurface properties and its signature in altimetric data. The ability of altimetry to monitor IPC pulses under any atmospheric conditions or when the SST signature is weak makes it an essential component for the IPC observing system in addition to satellite SST and moorings data.

Seasonality and interannual variability of the European Slope Current from 20years of altimeter data compared with in situ measurements

“…Caballero, Pascual, Dibarboure, and Espino (2008) analysed the current system in the southern Bay of Biscay with altimetry data, and found that the maximum sea level occurs in October while the minimum is in April. Le Henaff, Roblou, and Bouffard (2011) characterised the interannual variability of the SC flows along the northern coast of Spain in the winter and Herbert, Ayoub, Marsaleix, and Lyard (2011) also showed that the signature of the SC in the southeast corner of the Bay of Biscay can be depicted with altimeter data. Dussurget, Birol, Morrow, and De Mey (2011) studied eddy properties in the Bay of Biscay using fine resolution altimetry data from wavelet analysis.…”

Fine Resolution Altimetry Data for a Regional Application in the Bay of Biscay

“…For all considered altimetric missions (i.e., TP, J1, ENV and GFO), the 1 Hz rate data (equivalent to a resolution of approximately 6-7 km) have been reprocessed along the tracks using the coastal-oriented X-TRACK software ) whose objective is to improve both the quantity and quality of altimeter estimates in coastal regions by reprocessing a posteriori the Geophysical Data Records (GDRs) delivered by data assembly centers. Different studies have demonstrated the efficiency of the X-TRACK strategy in improving the data coverage and the representation of the coastal dynamics, characterized by relatively short-term and short-scale variations (Birol et al 2010;Le Hénaff et al 2010;Herbert et al 2011). The first step of the processing consists of redefining the data editing strategy on a regional basis to minimize the loss of data during the correction phase.…”

NEMO on the shelf: assessment of the Iberia–Biscay–Ireland configuration

“…18a, we also notice the warm current transport is highly variable at periods of a few days and may vary from no transport to more than 2 Sv over a short period. Such variability at daily timescales has been described by Herbert et al (2011) during the winter of 2004 from in situ observations and a numerical simulation. These authors suggest that the high-frequency variations are due to local wind forcing.…”