Time series of the Canary Current derived from one year of Pressure Inverted Echo Sounder (PIES) data

Abstract

Five pressure inverted echo sounders (PIES) have been deployed north of the Canary Islands at a nominal latitude of 29°N for 1 year to estimate a time series of volume transport of the Canary Current (CC) and the Lanzarote passage (LP) using the gravest empirical method (GEM). The GEM method even detected a Mediterranean eddy flowing through one of the PIES. The absolute geostrophic velocity at the eastern islands is predominantly southward, while at the western islands, the velocity fluctuates between southward and northward. The highest absolute geostrophic velocity occurs in the LP, gradually decreasing significantly offshore. Both the CC and the LP exhibit strong variability, with mean southward volume transport of −1.4 ± 1.6 Sv and −0.4 ± 1.1 Sv, respectively. The CC shows a consistent southward volume transport across all seasons, with stronger flow in summer (−2.5 ± 1.4 Sv) and autumn (−2.1 ± 1.0 Sv), when the CC flows across the entire archipelago. The CC is weaker in spring (−0.3 ± 1.4 Sv) and winter (−0.8 ± 1.1) flowing through the eastern Canary Islands with a northward recirculation along the western islands. The LP exhibits a southward volume transport in spring (−1.1 ± 0.8 Sv) and winter (−0.9 ± 1.0 Sv), with a northward recirculation of the CC in summer (0.2 ± 1.0 Sv) and autumn (0.1 ± 1.0 Sv). Volume transport estimates from historical hydrographic cruises generally agree with those obtained from the PIES data. A cross-correlation of 0.71 shows that the seasonal cycle in the LP corresponds well with the seasonal cycle of the Atlantic meridional overturning circulation.