by Chris Bryant

Dr. Paul Aharon regularly travels to two of the darkest places on the planet in an effort to shed light on the global warming debate.

The ocean's floor and the heart of a cave are two of the few places where you can experience a complete absence of light, and Aharon, a University of Alabama professor of geology and holder of the Ray E. Loper Endowed Chair in Geological Sciences, has spent much time in both locations.

On some 50 occasions since 1989, he's been part of selective research teams that have dived to the ocean's innermost depths — in the Gulf of Mexico and the North Atlantic Ocean. Inside submersibles, or small submarines, Aharon has traveled as deep as 7,000 feet during research dives that take as long as nine hours each.

"Navigating the ocean's floor is like being in the desert," Aharon said, "you don't have any bearings there. You have to try and use your sense of direction and your experience to find a specific target."

Aharon's targets are areas of recent and ancient hydrocarbon seepage on the seabed. These seeps are leaking significant volumes of crude oil or methane gas. The seeps include gas hydrates, which are frozen mixtures of methane gas and water. Frozen hydrates, Aharon said, pack 164 times more methane than in gas form, so they represent an enormous storage of gas on the seafloor.

At the low temperatures and high pressures typically found on the ocean's floor, these frozen mixtures are stable. However, if future global warming leads to higher ocean temperatures, more methane could be released from the gas hydrates into the water and up to the atmosphere, where it may act as a highly potent greenhouse gas and alter the global climate in an unprecedented way, the UA geologist said.

Aharon has often been granted time to use the submersible ALVIN, best known for its use in the discovery of the Titanic, for his dives. The sub, large enough only for a pilot and two scientists, is also equipped with a robotic arm. With the help of the robotic arm, the sub's lights, and its ability to cruise along the ocean's seabed, Aharon directs the pilot to retrieve specific cores of sediment from the seabed.

Despite the seriousness and the technical nature of the science involved, Aharon said he still gets caught up in the beauty and wonder of the ocean life that surrounds him.

"I turn off all the lights," Aharon said of his descents to the bottom of the ocean. "You can see all sorts of critters with unbelievable colors. It's a terrific feeling."

After obtaining the sediment cores, and then conducting various analyses, Aharon documents the presence of certain chemical markers. Later, Aharon compares those chemical markers with markers taken from other core samples and can often determine locations in the seabed where gas hydrates were once present but are not any longer.

Using a blow torch, Aharon seals gas from a hydrate in a glass tube.

These "missing" gas hydrates are indicators of previous occasions when different oceanic conditions existed and the methane, perhaps in large quantities, was released from the hydrates into the ocean and then into the atmosphere. Scientists are interested in pinpointing when conditions differed and how the methane was released. Locating clues related to the earth's climate at the time the methane was released gives the researchers insight as to the likelihood of similar occurrences in the future.

Aharon's exploration work on the ocean's floor has been funded by grants from NOAA/NURP (National Oceanic and Atmospheric Administration/National Undersea Program) and the Department of the Interior/Mineral Management Service — at the rate of $25,000 per day of the dive.

Just as the ocean's floor contains hidden secrets about the world's unstable climate, so too do the gloomy chambers inside caves. These ancient weather archives aren't found written in some cryptic man-made carvings on the cave's prehistoric walls, although they can be as difficult to decipher as if they were. Instead, these clues are found inside various cave deposits, known as speleothems, within the caves' confines. These speleothems, including the stalagmites and stalactites that are popular and readily visible to cave tourists, are up to hundreds of thousands of years old, Aharon said.

"They can serve as an archive of environmental conditions at a particular time," Aharon said of the cave deposits. They form when rainfall passes through soil and carbonate bedrock and enters the cave.

Aharon and Michael Rasbury, a UA geological sciences graduate student, spent three weeks in July collecting samples of cave deposits from the Polynesian island of Niue. Located just to the east of Fiji, and some 2,400 km northeast of New Zealand, Niue (pronounced new-ay) is home to approximately 1,700 people and a wealth of caves, many of which had never previously been explored by scientists. It's a carbonate island, meaning it is comprised of coral reef build-up, and, at 259 square kilometers, is said to be one of the world's largest carbonate islands.