Long-term and recent changes in sea level in the Falkland Islands

Mean sea level measurements made at Port Louis in the Falkland Islands in 1981-2, 1984 and 2009, together with values from the nearby permanent tide gauge at Port Stanley, have been compared to measurements made at Port Louis in 1842 by James Clark Ross. The long-term rate of change of sea level is estimated to have been +0.75 ± 0.35 mm/year between 1842 and the early 1980s, after correction for air pressure effects and for vertical land movement due to Glacial Isostatic Adjustment (GIA). The 2009 Port Louis data set is of particular importance due to the availability of simultaneous information from Port Stanley. The data set has been employed in two ways, by providing a short recent estimate of mean sea level itself, and by enabling the effective combination of measurements at the two sites. The rate of sea level rise observed since 1992, when the modern Stanley gauge was installed, has been larger at 2.51 ± 0.58 mm/year, after correction for air pressure and GIA. This rate compares to a value of 2.79 ± 0.42 mm/year obtained from satellite altimetry in the region over the same period. Such a relatively recent acceleration in the rate of sea level rise is consistent with findings from other locations in the southern hemisphere and globall

Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1 and -2

International audienceThis study focuses on the improved estimation of mesoscale surface ocean circulation obtained by merging TOPEX/Poseidon (T/P) and ERS-1 and -2 altimeter measurements between October 1992 and May 1998. Once carefully intercalibrated and homogenized, these data are merged through an advanced global objective analysis method that allows us to correct for residual long wavelength errors and uses realistic correlation scales of ocean dynamics. The high-resolution (0.25°×0.25°) merged T/P+ERS-1 and -2 sea level anomaly maps provide more homogeneous and reduced mapping errors than either individual data set and more realistic sea level and geostrophic velocity statistics than T/P data alone. Furthermore, the merged T/P+ERS-1 and -2 maps yield eddy kinetic energy (EKE) levels 30% higher than maps of T/P alone. They also permit realistic global estimates of east and north components of EKE and their seasonal variations, to study EKE sources better. A comparison of velocity statistics with World Ocean Circulation Experiment surface drifters in the North Atlantic shows very good agreement. Comparison with contemporary current meter data in various oceanic regimes also produces comparable levels of energy and similar ratios of northward and eastward energy, showing that the maps are suitable to studying anisotropy. The T/P+ERS zonal and meridional components of the mapped currents usually present comparable rms variability, even though the variability in the Atlantic is more isotropic than that in the Pacific, which exhibits strong zonal changes. The EKE map presents a very detailed description, presumably never before achieved at a global scale. Pronounced seasonal changes of the EKE are found in many regions, notably the northeastern Pacific, the northeastern and northwestern Atlantic, the tropical oceans, and the zonally extended bands centered near 20°S in the Indian and western Pacific Oceans and at 20°N in the northwestern Pacific

Multiscale variability in the Balearic Sea: an altimetric perspective

The present-day availability of an 18 year record of merged Mediterranean Sea sea level anomaly (SLA) data enables a contemporary description of long-term mesoscale activity in the Balearic Sea. SLA data from satellite altimetry are used to study the variability of sea level and surface geostrophic circulation at different spatial and temporal scales within this complex and relatively understudied region in the western Mediterranean (WMED). We find that the mean Northern Current along the Iberian slope is strongest in autumn, although higher variability in winter leads to stronger peaks in kinetic energy. The Balearic Current, which flows along the northern slopes of the Balearic islands, also has its maximum expression in autumn. Across the two Balearic channels (Ibiza and Mallorca), key locations that partly regulate meridional exchange in the WMED, observed seasonal variability in geostrophic velocity anomalies conforms rather well to prior descriptions, suggesting cautious confidence in the use of the Mediterranean merged altimeter product in nearshore regions. Circulation through the channels is maximum in winter. The channel data support the hypothesis that the channel circulation may be hindered by the intermittent presence of the Western Intermediate Water mass, which sometimes forms in winter in the Gulf of Lions. This is the first time that an analysis of variability in the Balearic channels has been performed using altimetric data.Evan Mason is supported by a Spanish government JAE-Doc grant (CSIC), cofinanced by FSE. This work has been partially funded by the project MyOCean-2 EU FP7Peer Reviewe