by Ali Hochberg / HONOLULU, HAWAII /
Understanding our planet and how it functions, as well as the impacts that human activities have on it, requires frequent and extended forays into the field to yield valuable data and observations. The COral Reef Airborne Laboratory (CORAL) investigation is a prime example. The three-year mission, funded by the NASA Earth Venture Suborbital-2 program, is conducting airborne remote sensing campaigns, along with in-water field validation activities, across four coral reef regions in the western and central Pacific Ocean.
“The objective is to conduct coral reef science at the ecosystem scale to find out the relationship between reef condition and the biogeophysical factors we think impact reefs,” said Eric Hochberg, CORAL principal investigator from the Bermuda Institute of Ocean Sciences, St. George’s, Bermuda. “With that understanding, we can build models to help scientists, resource managers and politicians gain a new perspective on reef function and better predict how natural and human processes will shape the future of reefs.”
When CORAL traveled to Hawai‘i last month for its second field campaign, it already had nearly a year of the mission under its belt. The Operational Readiness Test (ORT) took place in Hawai‘i last summer and the team completed a successful first field campaign in Australia’s Great Barrier Reef last fall. During both, communications between the airborne and field teams were streamlined, field operations and equipment deployments were tested and refined, and team members gained valuable experience working with both equipment and each other.
Even with years of planning and preparation, however, such ventures are always undertaken with the knowledge that some variables are out of the researchers’ control. For the CORAL team, there was one thing they couldn’t prepare for in Hawai‘i: the weather.
While the in-water field teams can—and do—work in what are often considered adverse conditions, the weather can still take a toll on the instruments left in the water to collect data.
“Our metabolism work on the fore reef of Kāneʻohe Bay was going well until a large north swell wrapped around to the windward side and toppled one of our gradient flux instrument stands,” said Robert Carpenter, CORAL co-investigator from California State University Northridge and leader of the reef metabolism team. “Luckily, it happened during the night before we were going to pick the instruments up, so we did not lose any data and the instruments were not damaged. Because of the swell, we continued the remainder of our data collection in the back reef and lagoon. So much for a calm time of the year!”
Unlike the in-water teams, the airborne operations for CORAL require substantially fairer conditions. The PRISM (Portable Remote Imaging Spectrometer) instrument that forms the backbone of the CORAL science is housed in the belly of a Gulfstream-IV airplane that flies over survey areas at an altitude of 28,000 feet. In order to obtain the most accurate spectral data possible from the seafloor, the airplane must fly in relatively cloudless skies with low surface winds over clear waters.
“One of the biggest operational challenges that the CORAL Hawai‘i campaign faces is the weather,” said CORAL project engineer Ernesto Diaz from NASA’s Jet Propulsion Laboratory, Pasadena, California. “For optimal data, a clear line of sight between the sun and the coral reefs is necessary, making clouds CORAL’s biggest enemy. Hawai‘i’s tropical location, the drastic topography differences within each island, and the trade winds, are some of the factors that make forecasting clear weather days particularly tricky. A clear day over an entire island is uncommon so we usually plan for collections over portions of the islands that have the best clear sky forecast, i.e. windward, or leeward sides. All of these factors make a successful data collection flight very rewarding.”
CORAL scientists also had to contend with a significant rain event over the region in late February as a slow-moving storm system dumped rain on the islands for two straight days and caused urban flooding in many areas. These floodwaters, originating on land and emptying into the surrounding ocean, led to a significant amount of soil runoff in areas. The additional sediment in the waters reduced water clarity and, as a result, impacted the ability of the PRISM instrument to “see through” the water to the seafloor.
Despite these challenges, the CORAL team was able to complete in-water validation activities in Kāneʻohe Bay and collect flight lines over the Big Island (the island of Hawai‘i), Maui, O‘ahu, Kaua‘i, Ni‘ihau, Moloka‘i, Lana‘i, and Kaho‘olawe. The benthic team also visited Maui and the Big Island to gather data for various benthic communities not represented in Kāneʻohe Bay.
“It was nerve-racking checking the weather forecasts each day and following the progress of the airplane, hoping for clear skies and calm waters over the different islands where we needed PRISM data,” said Hochberg. “We got some good breaks, though, and the Hawai‘i campaign was successful. Next month we get to start it all over again in Guam and Palau. I’m looking forward to it!”