The devastation caused by a hurricane when it strikes land can be seen for years or even decades. Hurricanes have a powerful effect on the oceans, which is less obvious but also less obvious.
In another review, we show through constant estimations that typhoons don’t simply agitate water at the surface. They can also send heat far into the ocean, locking it in for years and eventually affecting areas far from the storm.
The story’s most important element is heat. It has long been known that warm sea surface temperatures give hurricanes their energy. Because of this heat, clouds that are higher than Mount Everest are formed when moist air near the ocean’s surface rises like a hot air balloon. To this end, storms by and large form in tropical locales.
We discovered that hurricanes also increase the ocean’s capacity to absorb and store heat, thereby contributing to its eventual warming. Additionally, that may have significant repercussions.
Heat that is mixed into the ocean by hurricanes does not simply resurface in the same location. We demonstrated that storm-generated underwater waves can propel the heat approximately four times deeper than mixing alone, trapping it far below the surface. Deep sea currents can carry it thousands of miles from there. A hurricane that makes landfall in the Philippines after crossing the western Pacific Ocean could provide warm water that heats Ecuador’s coast for years.
At sea, looking for typhoons
In the fall of 2018, we lived aboard the research vessel Thomas G. Thompson for two months to observe how the Philippine Sea responded to shifting weather patterns. We study hurricanes and other tropical storms that cause turbulent mixing in the ocean as ocean scientists.
During the first half of our experiment, there were no clouds in the sky and no strong winds. However, in the second half, the ocean was agitated by three major typhoons—or hurricanes, as they are known in this region of the world.
How hurricanes draw energy from the ocean’s heat. Credit: Kelvin Ma via Wikimedia, CC BY
This shift enabled us to directly compare the ocean’s motions with and without the storms, via Wikimedia Commons, CC BY. We were particularly interested in understanding how heat was being transferred into the deep ocean by turbulence below the surface of the ocean.
A microstructure profiler, which uses a probe resembling a phonograph needle to measure the turbulent motions of the water while free-falling nearly 1,000 feet (300 meters), is the instrument we use to measure ocean turbulence.
What happens when a hurricane comes through.
Imagine the tropical ocean before a hurricane passes over it. At the surface is a layer of warm water, hotter than 80 degrees Fahrenheit (27 degrees Celsius), that is warmed by the sun and expands around 160 feet (50 meters) underneath the surface. Layers of colder water lie beneath it.
The waters are virtually incomparable because of the temperature difference between the layers. It’s analogous to the distinction made between oil and vinegar in an unopened bottle of salad dressing.
Similar to how a person shakes a bottle of salad dressing, hurricanes’ powerful winds help stir the boundaries between the water layers as they pass over the tropical ocean. Warm surface water is mixed downward, while cold deep water is mixed up from below. In the days following a hurricane, the ocean is able to absorb heat more effectively than usual because surface temperatures drop as a result.
Scientists have debated for more than two decades whether hurricanes’ downward mixing of warm waters could heat ocean currents and thus influence global climate patterns. The main question was whether hurricanes could pump heat far enough down into the ocean to keep it there for years.
We discovered that underwater waves transport heat approximately four times deeper into the ocean than direct mixing during hurricanes by analyzing subsurface ocean measurements taken before and after three hurricanes. The heat is transported sufficiently deep by these waves, which are created by the hurricane itself, to prevent its straightforward reentry into the atmosphere.
These illustrations show what happens to ocean heat before, during, after and many months after a hurricane passes over the ocean. Credit: Sally Warner, CC BY-ND.
Implications of heat in the deep ocean
These representations show what befalls sea heat previously, during, later, and numerous months after a tropical storm disregards the sea. Credit: Impacts of heat in the deep ocean Sally Warner, CC-BY-ND Once heat is picked up by ocean currents, it can travel to faraway parts of the ocean.
Following current patterns that move water from west to east across the equatorial Pacific, the heat injected by the typhoons we studied may have reached Ecuador’s or California’s coasts.
A combination of shoaling currents, upwelling, and turbulent mixing may now be used to bring the heat back to the surface. It is possible for the heat to warm the local climate and affect ecosystems once it reaches the surface once more.
Coral reefs, for instance, are particularly susceptible to prolonged heat stress. Although El Nio events are typically to blame for Ecuador’s coral bleaching, the excessive heat from the hurricanes we observed may have contributed to stressed reefs and bleached coral further away from the storms.
Additionally, it is possible for the excess heat generated by hurricanes to remain within the ocean for several decades or longer without reaching the surface. Climate change would actually be lessened as a result of this.
Hurricanes can help slow down the warming of the Earth’s atmosphere by redistributing heat from the surface of the ocean to deeper levels and keeping it in the ocean.
For a long time, scientists believed that hurricanes were extreme events caused by Earth’s climate and ocean heat. Our findings, which were published in the Proceedings of the National Academy of Sciences, add a new dimension to this issue by demonstrating that interactions occur in both directions—hurricanes have the power to heat the ocean and shape the climate of the Earth.
More information: Noel Gutiérrez Brizuela et al, Prolonged thermocline warming by near-inertial internal waves in the wakes of tropical cyclones, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2301664120
