Dr. Arnoldo Valle-Levinson is a Professor in the Civil and Coastal Engineering Department at the University of Florida and Chief Editor of Continental Shelf Research, and Associate Editor of Estuaries and Coasts, and Journal of Oceanography. He has published a textbook on estuarine hydrodynamics. He is also serving on the board of Our Santa Fe River.
It might be logical to assume that the middle of the ocean, say around Hawaii or the Azores, is completely disconnected from the water quality and quantity of Florida springs. However, the global ocean is interconnected through its fascinating system of currents and water levels. When the ocean’s water level sets above typical conditions (mean sea level), Florida springs become choked because their waters are unable to flush efficiently to the ocean. Within a few miles from the coast, springs and aquifers may be affected by a double whammy: the choking punch from the abnormally high-water level and a contaminating punch from salty water that intrudes into them.
It is evident, then, that the assumption of uncoupling between Florida springs and the open ocean would be faulty. This is a flawed notion because several processes in and on the Atlantic Ocean, such as gyres, water heating and cooling, winds, air heating and cooling, can affect the water levels around Florida. But really, the largest ocean process that impacts coastal water levels, and therefore the double whammy to the springs, is heating of ocean waters.
If we follow reliable information, we have probably read or heard that 2024 was the warmest year on record for the entire planet, i.e., it had the highest annual global average air temperature. This is the first time that the average temperature exceeds 1.5ºC above preindustrial levels, something that was not expected until the end of the 21st century! Furthermore, close to 90% of the warming in the planet occurs in the oceans.
Thanks to extensive measurements of water temperature throughout the upper 1.25 miles of the ocean we can determine that this layer of water has gained approximately 300 Zettajoules (that is a ‘3’ with 23 zeros in front) of heat since 1955 (see Figure below). Approximately 200 of those 300 Zettajoules have been gained in only the last 25 years! Obviously, that amount of heat means nothing without context. As reference, we know that the energy produced by one atomic bomb, like the one deployed in Hiroshima in 1945, is 15,000 billion Joules (that is, 1.5 with 13 zeros in front). So, the heat amount gained by the ocean in the last 25 years is equivalent to the heat released by the explosion of 13 billion atomic bombs! But even if that is too abstract, we know that there are 9,131.25 days in 25 years. Therefore, in the last 25 years, the ocean has gained heat that is the same as the heat released by the explosion of 1.46 million of atomic bombs PER DAY! And if that is still unimpressive, the energy gained by the ocean would power Miami-Dade County for 55 million years!
Amount of heat in the ocean’s upper 2000 m (1.25 miles) since 1955. The heat content is indicated by the black line, with its uncertainty (derived from water temperature measurements) in blue shades. The red shaded region denotes the last 25 years, with much reduced uncertainty.
Such amount of heat absorbed by the upper layer of the ocean in the last 25 years amounts to a temperature increase of ~1 degree Fahrenheit. It might seem like not much, but because of the ocean’s vastness the heat gain has caused increasingly powerful storms and widespread ecological impacts. Most important to regions near the coastline, the heat gain has caused the ocean to expand and rise around most coasts of the world, certainly throughout Florida. Consequently, rivers and springs are impacted by that extra elevation at the coast, sometimes causing backflows during periods of low river discharge and aquifer recharge. We’ll leave the topic of backflows for another post.
A fundamental question for humanity is why is the ocean, and the entire planet, gaining heat? Is it because we live in an interglacial period in the history of the Earth? Or is it because of greenhouse gas emissions? The first question involves natural variability, but the second question addresses human impacts. An ice core from Antarctica that is 2 miles long provides the distinction between natural and anthropogenic influences. This ice core has recorded the history of the Earth’s greenhouse gases in the last 800,000 years. In the ice core, the maximum concentration of carbon dioxide, the most abundant greenhouse gas in our atmosphere, had been 300 parts per million (ppm). The concentration goes up and down with glacial and interglacial periods that appear every 100,000 years. So the natural variability of carbon dioxide indicates that the maximum value is 300 ppm, but currently you can check the status at https://climate.nasa.gov/vital-signs/carbon-dioxide/?intent=121.
The current concentration is approximately 40% higher than at any time during the last 800,000 years. It is evident that such increase is anthropogenic. Most telling is the concentration of methane, another potent greenhouse gas, which has more-than-doubled its concentration relative to the maximum methane concentration in the ice record. There is no question or ambiguity that these anomalously high greenhouse gas concentrations have resulted from human activities, mainly linked to transportation, electricity generation, industry, agriculture, commercial and residential activities.
At the end of the day, human activities contribute to the warming of the ocean, sea-level-rise and choking of rivers and springs in Florida. We can address the challenging trend of the warming ocean, and planet, by contributing to reduce greenhouse gas emissions and by sharing this information with as many people as possible. The health and safety of Our Santa Fe is linked to our actions.
Dr. Arnoldo Valle-Levinson
Director, Our Santa Fe River
Incarnoldo@ufl.edu Tel. 352-294-7765
Dr. Valle-Levinson is a Professor in the Civil and Coastal Engineering Department at the University of Florida and Chief Editor of Continental Shelf Research, and Associate Editor of Estuaries and Coasts, and Journal of Oceanography. He has published a textbook on estuarine hydrodynamics.
