Signatures of Mid-Water ‘Jets’ in the Gulf Of Mexico BOEM NTL Dataset

摘要

We discuss the results of a process-oriented analysis of current profile measurements collected from 2005through 2010 in the Gulf of Mexico by oil industry operators, who are required to measure ocean currentprofiles and transmit these data in near-real-time. The individual data ensembles are sent to NDBC wherethey are processed, quality checked, archived and made available to the public through the NDBC website.WHG performed a thorough inspection of the data, including a review of the temporal and spatialcontinuity of the data, cross-check between neighboring stations and between current data and satellitealtimetry charts, and verification of the metadata using independent sources of [1].The cleaned and quality-controlled data were analyzed to identify and classify the observed cases ofstronger currents. The analysis identified 140 cases of current events characterized by a subsurface ‘jet’peaking at 30–50 cm/s that does not have a surface expression.. In most of the mid-water current eventsidentified in the 2005–2010 NTL data, the current speed peak is located somewhere between 300m and800m, most frequently around 500m, much deeper than similar patterns identified in earlier studies. Someof the events identified in our study lasted for less than one day, but many events were of a much longerduration. Most of these events were observed southeast of the Mississippi delta and had horizontal scalesover 15 miles and lingered in the area for an extended period of time. Some of the identified events werecaused by strong inertial oscillations with multiple speed peaks confined to a relatively narrow layercentered around 500m. Mid-water jets have been identified in previous work [2] but this new analysisprovides far more cases and suggests that the jets have an upper limit of about 50 cm/s. Such magnitudesare unlikely to govern extreme loads on offshore risers or tendons but they could be a factor in fatigue.