Abstract:

This dataset contains sea surface height anomaly (SSHA) determined from 72-hour low-pass filtered, 12-hour subsampled in situ data from an array of Pressure-recording Inverted Echo Sounders in the Gulf of Mexico from 2019-06-16 to 2021-05-19. Total SSHA as well as its two constituents, SSHA_ref determined from bottom pressure and SSHA_bcb calculated from geopotential height integrated to a common deep level for all sites, are provided at 12-hour intervals. Geopotential anomaly is calculated from 72-hour low-pass filtered travel time data and GEM lookup. SSHA_ref represents the contribution of mass loading. SSH_bcb results from density variability in the water column where bcb is shorthand for baroclinic referenced to the bottom. Diurnal, semidiurnal, lunar monthly and fortnightly tides were removed from the bottom pressure before calculating SSHA. The data are in NetCDF format. Associated data are available in datasets U1.x852.000:0003 (DOI: 10.7266/K4ZF1T9Z; currents), U1.x852.000:0004 (DOI: 10.7266/BZ9B3C54; pressure and temperature), U1.x852.000:0005 (DOI: 10.7266/4B13NKBA; vertical acoustic travel time), and U1.x852.000:0007 (DOI: 10.7266/GE30701Z; estimates of vertical profiles of temperature, salinity, and geopotential anomaly).

Suggested Citation:

Donohue, Kathleen, Randolph D. Watts, and Maureen Kennelly. 2022. Sea surface height anomaly determined from an array of Pressure-recording Inverted Echo Sounders (PIES) in the Gulf of Mexico, 2019-06-14 to 2021-05-19. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/2Q0KAAKG

Purpose:

Sea surface height anomaly data were calculated from in situ data from moored pressure-recording inverted echo sounders to increase understanding of the Loop Current (LC) separation process and to inform LC forecasting efforts.

Data Parameters and Units:

Time relative to 00:00:00 1 January 2019 (days), total sea surface height anomaly (meters), reference sea surface height anomaly (meters) and baroclinic referenced to the bottom sea surface height anomaly (meters).

Methods:

In situ vertical acoustic travel time data, round trip from the sea floor to the sea surface, and pressure data were acquired with URI and Sonardyne current and pressure-recording inverted echo sounders (PIES). Data were processed with URI's IES processing package version 4. Twenty-four pings obtained each hour were windowed to remove large outliers. Additional data spikes were removed. Hourly values were obtained as the average of a few pings around the first quartile of the remaining pings. Hourly pressure averages were calculated from six measurements taken at 10 minute intervals. An exponential-linear curve was fitted to determine instrumental drift. The drift curve was subtracted from the pressure measurements.Travel time and pressure data were 72-hour lowpass filtered. Estimates of vertical profiles of temperature and salinity were calculated from low-pass filtered travel time data and GEM lookup. A seasonal temperature GEM was added to the temperature profiles. Geopotential anomaly was calculated using the Matlab CSIRO Seawater Library routine sw_gpan.m using the seasonally corrected temperature profile and is calculated to be zero at the bottom. Geopotential anomalies were converted to their height equivalents in meters by dividing by gravity. Diurnal, semidiurnal, lunar monthly and fortnightly tides were removed from the bottom pressure before calculating SSHA. Pressures were converted to their height equivalents in meters by dividing by gravity and density. Total sea surface height anomaly is the sum of SSHA_ref and SSHA_bcb.

Instruments:

URI and Sonardyne current and pressure recording inverted echo sounders (PIES). The PIES is moored in a rigid anchor stand.

Provenance and Historical References:

Donohue, K. A., D. R. Watts, P. Hamilton, R. Leben, M. Kennelly, and A. Lugo-Fernandez. 2016. Gulf of Mexico loop current path variability. Dynamics of Atmospheres and Oceans, 76(2): 174–194, 2016. doi:10.1016/j.dynatmoce.2015.12.003 Hamilton, P., K. Donohue, C. Hall, R. R. Leben, H. Quian, J. Sheinbaum, and D. R. Watts. 2014. Observations and dynamics of the Loop Current. OCS Study BOEM 2015-006, U. S. Dept. of the Interior, Bureau of Ocean Energy Management, Gulf of Mexico OCS Region, New Orleans, LA. 417pp. Available online at https://espis.boem.gov/final%20reports/5471.pdf

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