Global warming and the ocean

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Posted on: March 9, 2022; Updated on: March 9, 2022
By Chris Horn, chorn@mailbox.sc.edu, (803) 777-3687

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The debate is over. Ninety-seven percent of climate scientists agree that Earth’s rising temperatures and related phenomena — more frequent and severe drought, flooding and wildfires — are a result of human-caused climate change. But humans can also be part of the solution, and there is a veritable army of researchers working to better understand, mitigate or adapt to the effects of climate change.

Two scientists who earned their Ph.D.s from South Carolina are gathering data on marine problems linked to global warming and the resulting increase in salinity and temperature of the oceans, which adversely affect coral reefs and could worsen other aspects of marine ecosystems.

Michelle Girach at the Jet Propulsion Laboratory is using airborne and satellite sensors to get a better perspective on coral reef health, while Ebenezer Nyadjro at NOAA’s Northern Gulf Institute is exploring the many side effects of rising ocean salinity.

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Michelle Gierach

Job: Scientist, Jet Propulsion Laboratory

Degree: Ph.D., marine science, 2009

Focus: Using satellite and airborne sensors to gather biophysical ocean data

Why it matters: New remote sensing technology is allowing scientists to gather sophisticated data sets that offer a holistic understanding of the health of aquatic ecosystems such as coral reefs.

Michelle Gierach’s research focus is underwater but her perspective is high in the sky. At least that’s where she deploys the airborne imaging spectrometers she uses to gather information about the health of Pacific coral reefs from the Great Barrier Reef in Australia to the main Hawaiian islands.

“Most coral reef assessments rely on scuba divers who can cover only a small area, translating roughly to less than 0.1 percent of the world’s reefs being mapped,” she says. As project scientist of the NASA COral Reef Airborne Laboratory (CORAL) mission, Gierach’s team increased this 20-fold. The data they gathered both confirms and refutes conventional wisdom about coral reefs. Some are bleached and degraded by environmental forces, such as rising temperatures, she says, but other reefs are very much alive and prospering.

“These airborne images are a fraction of what we’re going to get from space when spaceborne imaging spectrometers launch in the next few years.”

Gierach on the future: “Coral reefs throughout history have ebbed and flowed. Will there be some version of them going forward? Likely, but will they be as species-rich as they are now? That’s the real threat. Their survival ultimately affects everyone.”

 

Ebenezer Nyadjro

Job: Associate professor of research, NOAA Northern Gulf Institute, Mississippi State University

Degree: Ph.D., marine science, 2012

Focus: Ocean salinity

Why it matters: Global warming is affecting the saltiness of the ocean, which could affect marine fisheries, plastic pollution and ocean circulation.

When Ebenezer Nyadjro talks about his research, he sprinkles in a quick lesson on climate change. Global warming increases evaporation on the ocean’s surface, which makes for saltier water. But what goes up — evaporative moisture — must come down, and heavy rainfall makes other parts of the ocean less salty. Fluctuating salinity changes overall seawater chemistry and impedes the normal mixing of upper and lower strata. That means beneficial nutrients can get trapped below fish species that need them. Saltier seawater is also linked to more sluggish circulation.

“The amount of heat transported from warmer regions to colder regions is going to slow down,” Nyadjro says, pointing to the Gulf Stream current, which acts as a thermal conveyor from the Gulf of Mexico to Europe.

Nyadjro on the future: “We need data-driven decision making, and that’s hard to accomplish when we don’t always have sustained programming because of shifting political priorities. Data doesn’t lie, and current data shows that we are not moving in a good path.