Emma Heslop

Thermal Lag Correction on Slocum CTD Glider Data

AbstractIn this work a new methodology is proposed to correct the thermal lag error in data from unpumped CTD sensors installed on Slocum gliders. The advantage of the new approach is twofold: first, it takes into account the variable speed of the glider; and second, it can be applied to CTD profiles from an autonomous platform either with or without a reference cast. The proposed methodology finds values for four correction parameters that minimize the area between two temperature–salinity curves given by two CTD profiles. A field experiment with a Slocum glider and a standard CTD was conducted to test the method. Thermal lag–induced salinity error of about 0.3 psu was found and successfully corrected.

Autonomous underwater gliders monitoring variability at “choke points” in our ocean system: A case study in the Western Mediterranean Sea

Recent data from an autonomous ocean glider in the Ibiza Channel (Western Mediterranean Sea) show variations in the transport volumes of water over timescales of days-weeks, as large as those previously only identifiable as seasonal or eddy driven. High frequency variation in transports of water masses has critical implications for ocean forecasting. Three potential modes of transport are proposed, which have the potential to simplify the previously observed complex pattern of flows. Restricted ‘choke points’ between ocean basins are critical locations to monitor water transport variability; the Ibiza Channel is one such ‘choke point’, where variation in the transports of water masses are known to affect the spawning grounds of commercially important fish stocks.

Multiscale Observations of Deep Convection in the Northwestern Mediterranean Sea during Winter 2012–2013 Using Multiple Platforms

During winter 2012–2013, open‐ocean deep convection which is a major driver for the thermohaline circulation and ventilation of the ocean, occurred in the Gulf of Lions (Northwestern Mediterranean Sea) and has been thoroughly documented thanks in particular to the deployment of several gliders, Argo profiling floats, several dedicated ship cruises, and a mooring array during a period of about a year. Thanks to these intense observational efforts, we show that deep convection reached the bottom in winter early in February 2013 in a area of maximum 28 ± 3 109 m2. We present new quantitative results with estimates of heat and salt content at the subbasin scale at different time scales (on the seasonal scale to a 10 days basis) through optimal interpolation techniques, and robust estimates of the deep water formation rate of 2.0 ± 0.2 Sv. We provide an overview of the spatiotemporal coverage that has been reached throughout the seasons this year and we highlight some results based on data analysis and numerical modeling that are presented in this special issue. They concern key circulation features for the deep convection and the subsequent bloom such as Submesoscale Coherent Vortices (SCVs), the plumes, and symmetric instability at the edge of the deep convection area.

The Impact of New Multi-platform Observing Systems in Science, Technology Development and Response to Society Needs; from Small to Large Scales…

New monitoring technologies are key components of ocean observatories, also called marine research infrastructures being implemented in the worlds oceans. As a result, new capabilities to characterise, in quasi-real time, the ocean state and its variability at small scales exist today. The challenge is the integration of theses multiplatform observing and forecasting systems to (a) monitor the variability at small scales (e.g. mesoscale/weeks) in order to (b) resolve the sub-basin/seasonal and inter-annual variability and by this (c) establish the decadal variability, understand the associated biases and correct them. The challenge is also to change focus and now monitor from small to large scales. SOCIB is leading this new small to large-scale multi-platform approach in ocean observation. Some examples are presented and discussed together with initial ideas on the optimal design of an observational network in the world oceans, responding to science priorities, technology development and response to strategic society needs.

Assessment of High-Resolution Regional Ocean Prediction Systems Using Multi-Platform Observations: Illustrations in the Western Mediterranean Sea

High-resolution regional models of the ocean circulation are now operated on a routine basis using realistic setups in many regions of the world, with the aim to be used for both scientific purposes and practical applications involving decision-making processes. While the evaluation of these simulations is essential for the provision of reliable information to users and allows the identification of areas of model improvement, it also highlights several challenges. Observations are limited and the real state of the ocean is, to a large extent, unknown at the short spatiotemporal scales resolved in these models. The skill of the model also generally varies with the region, variable, depth and the spatiotemporal scale under consideration. Moreover, the increased spatial resolution might require ad hoc metrics to properly reflect the model performance and reduce the impact of so-called “double-penalty” effects occurring when using point-topoint comparisons with features present in the model but misplaced with respect to the observations. Multiplatform observations currently collected through regional and coastal ocean observatories constitute very valuable databases to evaluate the simulations. Gliders, high frequency radars, moorings, Lagrangian surface drifters, and profiling floats all provide, with their own specific sampling capability, partial but accurate information about the ocean and its variability at different scales. This is complementary to the global measurements collected from satellites. Using a case study in the Western Mediterranean Sea, this chapter illustrates the opportunities offered by multi-platform measurements to assess the realism of highresolution regional model simulations.