Is Tampa Bay in hot water?

Fred Pickhardt Aug 15

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According to a recent news article  Tampa Bay is facing some serious environmental issues. A massive untreated wastewater spill during Hurricane Debby has added to existing concerns about the health of the area’s estuaries. The storm overwhelmed the sewage systems, leading to millions of gallons of raw and partially treated wastewater spilling into streets, canals, and natural waterways.

Two day Storm Rainfall Totals

Turning on the Heat

The article further highlights that sea surface temperatures in Tampa Bay and nearby estuaries are rising significantly faster than the global average. It reports that in July 2023, surface water temperatures in Manatee Bay hit a record-breaking 101.1 degrees Fahrenheit. 

I decided to investigate the claims about the record high water temperature in Manatee Bay. The station reporting this temperature is part of a network of specialized observation sites in the Everglades, designed to monitor water depth and fresh water flow in shallow, mangrove-rich areas. 

The shallow waters of the Everglades experience significant temperature fluctuations due to varying amounts of sunlight, cloud cover, wind, and rainfall. The unusually sunny and dry conditions, along with lighter winds in the spring and summer of 2023, contributed to higher temperatures at the Manatee Bay site. It’s important to note that data from the Everglades Depth Estimation Network (EDEN), which tracks water levels across the freshwater Everglades landscape, is not suitable for comparison with ocean buoy data.

EDEN Manatee Bay Station | U.S. Geological Survey

What’s going on here?

Between 1970 and 2020, the sea surface temperature (SST) of the Gulf of Mexico increased by about 1.0°C (1.8°F), which corresponds to a warming rate of 0.19°C (0.34°F) per decade or 0.019°C (0.034°F) per year. Initially, SST anomalies in the Gulf of Mexico and the Atlantic tracked closely with the global SST trend. However, since around 1990, these anomalies have started to rise more rapidly. This time period also marks the beginning of the warm phase of the Atlantic Multidecadal Oscillation (AMO), which is likely contributing to the accelerated warming in both the Atlantic and the Gulf of Mexico.

Ref https://journals.ametsoc.org/view/journals/clim/36/8/JCLI-D-22-0409.1.xml

Rapid Ocean Warming in 2023

The article cites meteorologist Brian McNoldy from the University of Miami, who notes that the Gulf of Mexico’s temperatures “really went off the rails last spring, and they haven’t gotten back to the rails since then.” I concur that the 2023 water temperatures indeed were exceptionally high.

In my view, the unusual warming in the North Atlantic, particularly in tropical and subtropical regions, is largely attributable to a combination of factors. Firstly, the Atlantic Multidecadal Oscillation (AMO) is in its warm phase, which raises baseline sea surface temperatures in the North Atlantic. Secondly, the effects of an El Niño event and unusually weak trade winds have also played significant roles.

During 2023, sea surface temperature (SST) anomalies in the Tropical North Atlantic surged notably in the spring and summer. This warming can be attributed to the weakening and southward displacement of the Azores-Bermuda ridge as shown below in the June 2023 surface pressure anomaly chart. This ridge’s weakening diminished trade winds, leading to reduced upper-ocean mixing and evaporative cooling. Concurrently, there was less cloud cover and Saharan dust, fewer sulfate particles due to cleaner shipping fuels, and increased stratospheric water vapor from the Hunga-Tonga undersea eruption. These combined factors facilitated the rapid warming of the ocean surface.

  June 2023 Surface Pressure Anomaly

Tampa Bay Sea Surface Temperatures

Have sea surface temperatures (SSTs) in Tampa Bay been rising significantly faster than global averages and even those in the Gulf of Mexico?

To address this, I examined the average SSTs for July and August, which are typically the warmest months in Tampa Bay, to determine if there is an accelerated warming trend. Using data from “seatemperature.info,” it is evident that SSTs in Tampa Bay for July and August 2023 were notably higher than in previous years, with data available from 2007 onward.

Note Purple dot denotes El Nino Year

Source: https://seatemperature.info/july/tampa-bay-water-temperature.html

A quick calculation indicates that the warming trend for Tampa Bay from 2007 to 2022 was approximately 0.07°F per year which is about twice the longer-term rate of 0.034°F per year (1970-2020). However, including the 2023 data, the trend rises to 0.10°F per year, representing an increase of about 43%. This suggests that the temperatures in July and August of 2023 were anomalously high, and incorporating this data might skew the long-term warming rate.

To better understand whether 2023 represents a one-time anomaly due to a rare combination of natural factors or signals a shift in the longer-term warming trend, it would be prudent to wait a few more years. This additional time will help clarify whether the observed increase is part of an ongoing trend related to climate change or an isolated event.

Fred Pickhardt

Ocean Weather Services

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548 Market Street PMB 72296, San Francisco, CA 94104