Sixty years ago, marine scientists aboard ships from 14 countries combined efforts to explore the largest unknown area on earth, the Indian Ocean. The expedition generated a wealth of information and formed the basis of our modern understanding of the Indian Ocean basin.
Beginning next week, an Australian voyage will retrace part of the that historic International Indian Ocean Expedition to reveal the effects of climate change on the physics, chemistry, and biology of the waters of the southeast Indian Ocean and produce a unique snapshot into how much the oceans’ marine life has changed over time.
University of Maryland Center for Environmental Science professor and biological oceanographer Raleigh Hood will be among the 40 marine scientists and technicians from 18 institutions who will spend 32 days at sea on this second International Indian Ocean Expedition (IIOE2), led by Professor Lynnath Beckley from Murdoch University in Australia, beginning May 14.
They will leave from Freemantle Australia near Perth and work their way north all the way to Jakarta, sampling along the 110°E longitudinal meridian in the deep ocean—approximately 500-600 km offshore of the continent—passing through big waves and wind in the southern ocean to temperate and productive tropical waters and even stunning blue waters of the southern Indian Ocean subtropical gyre. Researchers will study the entire marine food web from phytoplankton to whales, including currents and chemistry, and will make direct comparisons with data from the expedition 60 years ago.
“We are all aware of the potential negative consequences of global warming and warming of the oceans. The Indian Ocean seems to be accumulating heat faster than the other ocean basins,” said Hood. “We look at it as a canary in the coalmine in terms of how ocean ecology and chemistry might be impacted by warming and acidification.”
The Indian Ocean drives the region's climate, including extreme events such as cyclones, droughts, severe rains and waves. Research and observations supported through the Second International Indian Ocean Expedition will result in an improved understanding of the ocean's physical and biological oceanography, and related air-ocean climate interactions.
“There hasn’t been very much research along the lines of what we’re doing now to try to understand how the Indian Ocean is changing, so we are at the vanguard of efforts to do that,” said Hood.
Hood has been involved in Indian Ocean activities for decades, doing a combination of modeling and observational work in the Bay of Bengal and Arabian Sea. He coauthored one of the first biogeochemical models of the Indian Ocean more than 20 years ago and founded the Sustained Indian Ocean Biogeochemistry Ecosystem and Research Program to encourage research in the region. He was one of the principal people who motivated this expedition.
“We construct models and run them in the Indian Ocean to simulate physical and biological processes and we can compare those models with observations—both in situ and satellite. If you can get your model to reproduce what you see in the ocean, you can use the model to sort out what’s going on,” he said. “Once you capture that variability, you can take the model apart and say why it is this happening.”
On the cruise, Hood will be working with Scripps Institute of Oceanography biological oceanographer Mike Landry, an expert on marine food webs, to quantify zooplankton grazing control on phytoplankton. They will take samples of water from various depths in the upper ocean and manipulate them on the on deck of the research ship using incubators to control temperature and the light, removing a few grazers at time to sort out how phytoplankton growth is impacting by zooplankton. They will also be taking isotopic measurements aimed at understanding how nutrients are propagating through the food web.
“The Indian Ocean is super complicated and not very well understood. It’s really complex in terms of physical and biological dynamics,” said Hood. “It’s is the final frontier of the final frontier.”
The voyage leaves on May 14 and returns on June 14.