Project seeks climate clues deep in Indonesian lakebed

11 June 2015

A project aimed at sampling pristine sediments from deep beneath an ancient Indonesian lake is in full swing since May. A team co-led by OCCR researcher Hendrik Vogel is currently drilling from the floor of the freshwater Lake Towuti all the way down to bedrock. The sedimentary cores they produce could hold a million years of climate and environmental data and help scientists reconstruct the climate history of a region that wields a weighty influence on global climate.

The international team of geoscientists drilling sediment cores on the island of Sulawesi, in Indonesia consists of 40 scientists. The drilling will last about two months and runs 24 hours a day. The drilling is done from a big barge, floating in water as deep as 200 meters. A local mining company called PT Vale Indonesia is providing logistical help with the drilling operation. The cores themselves come up in 3-meter sections, and a team of scientists is processing the cores as they come aboard, preparing them to be shipped to labs the world over for analysis.

Lake Towuti is the largest of a string of ancient tectonic lakes that dot the landscape of Sulawesi. “These lakes were identified 20 years ago as high priority sites for a scientific drilling program,” said James Russell, a Brown University geologist and co-leader of the Lake Towuti Drilling Project. “They’re big, they’re known to be very old, they comprise a very unique chemical composition, and they’re in a climatically important region of the world.”

Water vapor plays a key role in regulating global temperature

The Indonesian archipelago sits within a pool of warm ocean that controls the Pacific El Niño oscillation, which can alter temperature and rainfall patterns across the Americas and elsewhere. The warm pool also supplies a substantial proportion of the water vapor in the Earth’s atmosphere. Water vapor is the planet’s predominant greenhouse gas, so the water vapor supply coming from the Indonesian waters likely plays a key role in regulating global temperature.

“What we really want to know is, if you go back through time, how does the hydrological cycle of the biggest single source of global water vapor vary during periods of global climate change- that’s a very important feedback to consider in thinking about past climate change as well as future predictions”, Russell said. “We are also interested in how these hydrological changes alter the landscape and soils surrounding Lake Towuti; a better understanding of these processes and their rates of change is very important when considering future climate projections for this densely populated region of our planet”, said Vogel, a University of Bern geologist and co-leader of the Lake Towuti Drilling Project.

The signatures of that hydrological cycle and its effect on landscape development have been trapped over time in the sediment of Lake Towuti, and are detectable in the sediment cores the researchers will gather. By looking at how concentrations of different chemical markers in the sediment change with depth, the researchers can develop a continuous record through time of how much surface runoff and with it soil substrates poured into the lake. The rate of runoff is directly related to the rate of rainfall.

Test predictions made by climate models

A preliminary drilling operation completed in 2010 showed that changes in the hydrological record are indeed detectable. In the initial operation, Russell and Vogel and their teams cored about 20 meters into the sediment and recovered a record of about 60,000 years of rainfall. That work showed that during the last ice age, when glaciers covered much of the northern hemisphere, Indonesia dried out substantially. Rainfall in the region during that period tailed off by as much as 50 percent, the researchers found.

“We’ve documented drought during one ice age, but there have been dozens of ice ages spanning the last million or so years,” Hendrik Vogel said. “We’d like to see if we can replicate that finding. As the Earth warms or cools, does Indonesia consistently become wetter or dryer?”

The current phase of the project could answer those questions. Rather than stopping at 20 meters, the Towuti Drilling Project will drill all the way to bedrock, through as much as 200 meters of sediment and perhaps a million or more years of time. The information gathered on Indonesia’s hydrological cycle could then be used to test the predictions made by climate models and better predict future climate change.

The scientists are posting updates throughout the operation on the project’s Facebook page:

(Source: Kevin Stacey,  Brown University)