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Spotter Data Spotlight: Gulf of Mexico

Melanie Feen

The Gulf of Mexico is a busy body of water. It is a key international maritime corridor, the drainage basin for the mighty Mississippi River, the center of the U.S. petroleum industry, and the coastal home of over 15 million people (McKinney et al, 2021). Its economic and environmental importance, both domestically and abroad, cannot be overstated.

Understanding the Gulf’s weather and hydrology, therefore, is paramount, and accurate, real-time ocean data is the key to comprehension. Such actionable insights allow us to monitor complex currents, hurricanes, the spread of pollutants, fisheries, etc., and better equip the Gulf region to protect its marine ecosystem.

Sofar Ocean is a key player in this data collection effort. Sofar had 24 Spotter buoys deployed in the Gulf of Mexico from October 22nd, 2021, to January 31st, 2022, each of which gathered compelling wave and sea surface temperature insights as it drifted throughout the region. Below, we’ll discuss what these Spotters revealed about the Gulf of Mexico’s Loop Current and highlight their top notch wave monitoring performance, particularly during severe weather.

The Loop Current

When the warm, salty waters of the Gulf Stream flow through the Yucatán Channel and into the Gulf of Mexico, the current’s path can vary with time. Sometimes, the warm water current flows into the Florida Strait and up along the East Coast of the U.S. Other times, the current forms a loop within the Gulf itself, a phenomenon known, conveniently, as the Loop Current. In the visualization below, watch as three Spotter buoys gradually drift through the Florida Strait and up the eastern seaboard, while multiple buoys enter the Loop Current, visible as a hollow orange loop in the eastern section of the Gulf. Note: each black dot represents a Spotter and each colored marker represents an observation of sea surface temperature: redder means warmer, bluer means colder.

Sometimes, when the Loop Current migrates far enough west into the Gulf of Mexico, eddies — ocean currents moving in circular patterns — will form and split off from the current. In the visualization below, watch as one of the Spotters travels in both a Loop Current eddy and the Loop Current itself. The subsequent screenshot identities the location of each.

Spotter “SPOT-010136” (orange path) starts in the Loop Current eddy before drifting into the Loop Current itself. Eventually, the Spotter travels through the Florida Strait and up the eastern seaboard.

What is the significance of the Loop Current and its eddies? The warm water of each feeds storms with heat, giving them the energy they need to intensify. During the devastating Hurricane Katrina, for example, the Loop Current and a Loop Current eddy increased the storm’s strength (Goni et al., 2009). Knowing this, real-time monitoring of the behavior of the Loop Current and its eddies is critical, a task that Sofar’s Spotter network, as demonstrated above, is equipped to take on.

Wave Forecasts

Accurate wave forecasts are critical for a variety of stakeholders, including the maritime industry, the government, coastal communities, and oceanographers, amongst many others. To improve wave forecasts in the Gulf of Mexico (and across the globe!), Sofar assimilates buoy spectral wave data into global operational wave forecasts. By comparing predicted significant wave heights to buoy measured wave heights in the Gulf during the October 22nd, 2021, to January 31st, 2022, Spotter deployment period, the performance of Sofar’s Operational model can be evaluated against NOAA’s Global Forecast System (GFS).

Relative to NOAA GFS forecasted significant wave height, the Sofar model showed improvements across all forecast hours, meaning it predicted values closer to the true significant wave heights measured by the Spotter buoys. The most significant improvement was observed in nowcast measurements, which is logical because Sofar’s data assimilation step improves upon the initial model using real-time observations. In turn, the improved initial model produced more accurate forecasts, even just two days into the future!

The NOAA Forecasts (yellow) have larger error (RMSE) for all forecasted hours compared to the Sofar Operational model (blue). Lower error means that the Sofar model predicts values closer to the true significant wave heights measured by our Spotter buoys.


Additionally, the Sofar model performed particularly well during severe weather. During a storm on January 16, 2022, for instance, Spotter buoys measured significant wave heights upward of 5.6 m (18.4 ft). Global forecasts underestimated the waves associated with this low pressure system, producing a nowcast with waves 0.5 m (1.6 ft) smaller than the waves predicted by the Sofar model.

As the Spotter buoy network continues to grow, so too will Sofar’s ability to track weather activity in the Gulf of Mexico. By assimilating observations from Spotter buoys and bringing models’ initial states closer to observed values, the Gulf region will be better prepared to monitor currents, track hurricanes, and safeguard coastal communities and economies.

For more insights, check out the Sofar blog.

References:

Goni, Gustavo, Mark DeMaria, John Knaff, Charles Sampson, Isaac Ginis, Francis Bringas, Alberto Mavume et al. "Applications of satellite-derived ocean measurements to tropical cyclone intensity forecasting." Oceanography 22, no. 3 (2009): 190-197.

McKinney, Larry D., John G. Shepherd, Charles A. Wilson, William T. Hogarth, Jeff Chanton, Steven A. Murawski, Paul A. Sandifer et al. "The Gulf of Mexico." Oceanography 34, no. 1 (2021): 30-43.

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