| dc.description.abstract | In February of 2021, a series of winter storms moved across the southern continental United States, resulting in extreme cold temperatures on land and in coastal waters. The Texas Automated Buoy System (TABS) network recorded a sea surface temperature minimum of 10.73°C and a surface density maximum of 1025.25kg/m3 south of Galveston Bay shortly after the winter storms, unusual values when compared with TABS’s decades-long measurements in the coastal northwestern Gulf of Mexico. Hydrographic profiles collected in April 2021 in the same region show the presence of an anomalous subductive tongue: a distinct water mass characterized by an isohaline of 36.2 and density range 25.2kg/m3 – 25.8kg/m3 moving seaward from the full water-column along the continental shelf and subducting beneath the mixed layer at depths ~30 – 60m. The signal of the tongue diminished by September 2021 after being incorporated into background values. We have shown via various analyses and quantification of observations from 1995-2023 that the 2021 hydrography deviates from climatological values due to the presence of the water mass, substantiating the density anomaly of the tongue. 2021 observations allow us to connect the April tongue with the February winter storms, revealing the spatiotemporal extent of the event. Numerical hindcast results show that atmospheric forcing, particularly cooling and vertical mixing due to winds that resulted in homogenous water-columns, resulted in the formation of a surface dense water mass in the northwestern Gulf of Mexico. Analyses in temperature-salinity space shows that after formation along the shelf in February, the water mass mixed diapycnally with ambient water as it moved offshore and sank down the water-column, reaching neutral buoyancy under the upper mixed layer by April. | |
