302: Arctic Coring Expedition (ACEX)

Figure 1. Map of the arctic ocean showing the locations of the EXP 302 study area on the Lomonosov Ridge. The small-scale map shows the locations of EXP 302 sites. Figure from IODP Expedition 302 Summary.

In 2004, The Integrated Ocean Discovery Program (IODP), completed its three-hundred-and-second expedition located in the central Arctic Ocean at Lomonosov Ridge, about 250 km from the North Pole (Figure 1). During this expedition, the scientists and crew were able to recover sediment cores from three (M0002—M0004) out of the four holes they drilled (Figure 2F). The recovered sediment core depth was up to 428 meters below the seafloor. The main objective for this expedition was to further study the ancient ocean currents and ocean behavior (paleoceanography) of the Arctic region, specifically to better understand the past climate of the central Arctic Ocean and its impact during the Cenozoic Era (66 million years ago to today), when the Earth changed from a “Greenhouse” world (a time when there is very little to no ice on Earth) in the Eocene (~41 million years ago) to an  “Icehouse” world (a time when there is extensive ice) of today.

During Expedition 302, the primary objective was to continuously recover sediment records (cores) and to sample the underlying bedrock by drilling and coring from the stationary drillship. This was not an easy task because of the prominent moving heavy sea ice at the Lomonosov Ridge. In order to prevent the ice from complicating the mission, a fleet of 3 icebreaker ships were used: The drilling vessel the Vidar Viking, a nuclear Russian icebreaker Sovetskiy Soyuz, and a diesel-electric icebreaker Oden. The primary goal of the icebreakers was to protect the drilling ship to ensure smooth drilling and coring operations. 

Figure 2. Seismic reflection profile of the Lomonosov Ridge (AWI-91090) with locations of Expedition 302 coring sites. Multichannel seismic data are from Jokat et al. (1992). Cores were not retrieved from Hole M0001A because the BHA (gray on figure) was lost. Hole M0004B is located ~60 m away from Hole M0004A; Hole M0004C is located ~60 m away from Hole M0004B. SP = shotpoint. Image from IODP Expedition 302 Summary.

The scientific objectives of Expedition 302 are split between paleoceanography (reconstructing ancient ocean conditions) and tectonics. 

The paleoceanographic objectives included:

  • Determining the history of sea ice and ice rafting in the region
  • Studying the differences between local and regional ice development
  • Determining the density structure (related to temperature and salinity) of the Arctic Ocean surface waters
  • Determining the timing and consequences of the opening of the Bering Strait 
  • Studying the land-sea links and the response of the Arctic to the Pliocene (~5.3–2.58 million years ago) warming events
  •  Investigating the development of the Fram Strait and deepwater exchange between the Arctic Ocean and Greenland/Iceland/Norwegian Sea (Figure 3)  
  • Determine the history of biogenic sedimentation (sediments made by organisms). 

The tectonic objectives included:

  • Investigating the nature and origin of the Lomonosov Ridge by sampling the oldest rocks below the regional unconformity (a time when there are no sediments that represent a specific time interval in the sediment and rock record) in order to establish the pre-Cenozoic environmental setting of the ridge 
  • Studying the history of rifting and the timing of tectonic events that affected the ridge.
Figure 3. Generalized schematic of sea ice transport in the Arctic Ocean. Red contours denote average years of residence time before sea ice export through the Fram Strait. Arrows indicate average transport speeds. Figure from IODP Expedition 302 Summary.

IODP Exp. 302 was the first ever drilling project that was able to drill in this location, making the results pretty revolutionary. Not only were they able to gain information on all of their objectives, they also gained information on the Paleocene/Eocene Thermal Maximum (PETM; ~55.5 million years ago). This boundary was recovered during the drilling and it represents a time when the temperature of the Arctic Ocean waters exceeded 20°C or 68°F. The efforts put into this expedition made great advancements in science since this is the most cited IODP cruise!  


Backman, J., Moran, K., McInroy, D.B., Mayer, L.A., and the Expedition 302 Scientists Proceedings of the Integrated Ocean Drilling Program, Volume 302. http://publications.iodp.org/proceedings/302/302toc.htm.

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