Earth’s Climate And Ocean Acidification History

The Integrated Ocean Drilling Program drillship JOIDES Resolution has returned to Honolulu after a two-month voyage to chart the detailed climate history of the Earth. This was the first of two voyages of the ‘Pacific Equatorial Age Transect’ project, and the first international scientific drilling expedition since the JOIDES Resolution underwent a multi-year, more than $100-million transformation into a 21st century floating science laboratory. Onboard were 29 scientists from seven nations, 25 technicians, and an international crew of 66.

The first expedition, led by Heiko Pälike of the University of Southampton’s School of Ocean and Earth Science, based at the Centre, and Hiroshi Nishi (Sapporo, Japan), ended on 4 May after successfully coring over 3.5 km of the sediments and rocks from below the Pacific Ocean seafloor. A second expedition to the equatorial Pacific will depart Honolulu, Hawaii, on 9 May and will recover sediment cores from the seafloor at three more drilling locations.

The entire scientific team is made up of 60 scientists from over 15 different countries and represents scientists at every stage of their career from graduate students to senior professors. Scientists, drillers, and technical staff participated in live interactive video conferences with enthused students and teachers who learned about the expedition’s discoveries, ocean drilling, and life at sea. The scientists supported by the UK are Heiko Pälike, Paul Wilson, Edgar Kirsty (National Oceanography Centre, Southampton), Paul Bown and Tom Dunkley Jones (University College London), and Peter Fitch (University of Leicester).

The scientists are using mud and rocks from far below the equatorial Pacific Ocean floor to uncover details about the climate history on Earth. The sediment layers recovered from six drilling locations act like pages from a book, and record inch-by-inch Earth’s climate history. The two-month expedition succeeded in obtaining records ranging from the present to the warmest sustained ‘greenhouse’ period on Earth around 53 million years ago. At that time, alligators lived as far north as the Arctic, and palm trees grew in the Rocky Mountains. Reconstructions have shown that there were no significant polar ice caps, and greenhouse gas concentrations were several times higher than today.

The super-greenhouse early Eocene was followed by gradual cooling and the sudden buildup of major ice caps on Antarctica around 34 million years ago, leaving its mark in the equatorial sediment cores that the scientists are bringing back to Hawaii. The voyage discovered the effect of large-scale climatic changes on the oceans of the past. 53 million years ago, carbon dioxide in the atmosphere was much higher than today, and made the ocean much more acidic, such that only little carbonate is preserved in sediments recovered from those times. In contrast, during the buildup of ice on Antarctica, the ocean became less acidic very rapidly, and more carbonate was suddenly preserved in the deep ocean. The transition from warm to cool climates took place in less than 100,000 years – well within the time span that humans have been living on our planet.

The onboard studies revealed that changes in ocean acidification, linked to climatic change, have a large and global impact on marine organisms. Co-Chief Scientist Heiko Pälike remarked: “It is truly awesome to see 53 million years of Earth’s history pulled up onto the drill ship’s deck, and then to pass through our hands and past our eyes. We saw the effects of Earth’s climate machine in action. Ocean drilling is the equivalent of the space programme to the Earth Sciences, and this truly international exploration would not have been possible without more than 40 years of scientific drilling research helping us find the best places to drill.”

Because of the important role of the equatorial Pacific in climate processes, environmental changes are recorded by shells of microfossils the size of a pinhead that make up the sediments, which the international group of scientists have now brought from more than three miles below the sea surface onboard the unique scientific drilling vessel JOIDES Resolution.

“We can use the microfossils and layers of this superb sediment archive as a ‘yardstick’ for measuring geological time. This will allow us to determine the rates of environmental change, such as the rapid first expansion of large ice-sheets in the Antarctic 33.8 million years ago,” said Expedition Co-Chief Scientist Hiroshi Nishi. “This polar process had a profound impact on phytoplankton even at the Equator. We managed to catch several records of this important climatic transition.”

The JOIDES Resolution is a research vessel with unique capabilities for exploring and monitoring the sub-seafloor; it operates as part of the Integrated Ocean Drilling Program (IODP). IODP is supported by the US National Science Foundation and Japan’s MEXT. Additional programme support comes from the European Consortium for Ocean Research Drilling (ECORD) to which the UK Natural Environment Research Council (NERC) contributes. Other contributors are India (Ministry of Earth Sciences), the People’s Republic of China (Ministry of Science and Technology), the Republic of Korea (Korea Institute of Geoscience and Mineral Resources), Australia and New Zealand. The JOIDES Resolution is now poised to help IODP continue to push the envelope of science by collecting unique sub-seafloor samples and data that would otherwise remain out of reach to researchers.