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Abstract

A 34-Year Historical and Altimetric Perspective of Loop Current Intrusion and Eddy Separation in the Gulf of Mexico

Pr Robert LEBEN(1), Mr Cody HALL(1), Mr Gabriel LODOLCE(1)

(1) CCAR/University of Colorado Boulder, United States

Session theme: Others (Posters only)

  • poster

    Abstract

    Continuous altimetric monitoring of Loop Current intrusion and eddy separation in the Gulf of Mexico has been possible since ERS-1 was placed in the multidisciplinary 35-day repeat orbit in April 1992. In the 20-year time period since then a total of 30 major anticyclonic eddies have separated from the Loop Current, which gives an average separation period of 8 months over the continuous altimetric record. A recent reanalysis of the available satellite and industry observations back to July 1978 found 19 additional eddies giving a total of 49 separation events over the 34-year record or an average separation period of 8.4 months. The average separation period is thus relatively stable over the more than three decades of observation; nevertheless, the time interval between separation events is quite irregular, exhibiting a range from 2 weeks to over 18 months. Over a dozen dynamical mechanisms have been proposed to explain eddy separation; however, no Loop Current eddy separation precursor had been identified until Loop Current retreat following eddy separation was shown to be a good predictor of the subsequent eddy separation period. A simple Loop Current vorticity model provides a theoretical basis for this empirical relationship. After suitable scaling approximations, the theory predicts that the Loop Current separation period is a linear function of retreat latitude, which agrees well with altimeter-derived empirical results. The regressions results show that this relationship is statistically stable over the 34-year record, as would be expected of a physically controlled phenomenon. Other Loop Current statistics show similar stationarity. A histogram of separation times binned by month shows a clear seasonal signal in the monthly distribution with separation occurring more often in late winter/early spring and late summer/early fall, with 'fall' separation events being 50% more likely than 'spring'. The stationarity of the Loop Current separation period and retreat latitude statistics, including the seasonality of the separation times, over the 34-year record is remarkable and is the most significant result found in this analysis of the historical and altimetric records. In honor of the 34-year anniversary of the launch of Seasat and the progress in radar altimetry, we will highlight satellite observations of the initial separation event in our record using Seasat synthetic aperture radar imagery and radar altimetry from July 1978.

     
    Corresponding author:

      Pr Robert Leben
      CCAR/University of Colorado Boulder
      431 UCB
      80309-0431 Boulder
      United States
      E-mail:
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