Clipperton 2008 Sampling Trip

In late February of 2008, we joined forces with a group of amateur radio operators or "hams" in order to share in the logistics and costs of chartering a boat to bring us to Clipperton Atoll.  Our science team consisted of Dr. Julian Sachs, his graduate students Daniel Nelson and Alyssa Atwood, and a graduate student of French scientist Dr. Eduard Bard - Olivier Cartapanis.  The science goals were to collect a series of water and suspended particle samples from the brackish lagoon in the center of the Atoll, as well as to attempt to collect sediment cores of whatever material might be present within the lagoon.  These samples would be used by our group in an effort to expand ongoing work on the effects of salinity on the hydrogen isotopic composition of biomarkers in the aquatic environment, and possibly also to help address working hypotheses about the position and strength of the Inter-Tropical Convergence Zone (ITCZ) through the paleo-record.

The radio team was on a "dxpedition", which is one aspect of ham-radio where enthusiasts travel to remote, and often dangerous locations in order to establish a temporary broadcasting point.  This creates and opportunity for other enthusiasts to contact people in a remote location in the world.  This allows them to expand the number of locations that they have contacted, and to improve their standing in the ham radio community.  For more information on this group's activities, see partnership provided us with a unique opportunity to experience ham-radio, and to meet a great group of people.

We left for Clipperton Atoll aboard the Shogun out of San Diego, a boat that typically conducts sport-fishing charter trips.  The voyage to and from the island was about one full week in each direction, giving us just under two weeks to unload all of the radio and science equipment from the boat, and to work on-site for approximately ten days.  Equipment transfer proved to be a rather difficult process as Clipperton possesses no natural harbors and is surrounded on all sides by shallow reef.  For these reasons the cargo loads on the skiffs had to be kept to a minimum and gear shuttling had to be suspended during the apex of low-tide conditions.  The Shogun crew did a great job getting everything to shore, in spite of all the injuries and damaged equipment that they suffered in the process from cuts on the sharp coral, to broken propellers, to skiffs overturning in the surf, they really did an excellent job in working through.

On the island we experienced an environment dominated by boobies, crabs, garbage, and extreme weather.  In our short stay we were subjected to a wide range of weather extremes including high heat/humidity, torrential rains, high winds, blazing sun, and severe sunburn.  More than one tent collapsed due to high winds.  Jean-Pierre, a French radio operator installed a weather station while we were on the island.  Check here to see some data.

After some initial false starts, we finally got a feel for the sediments and began recovering quality cores.  As circumstances turned out, Julian and Dan ended up collecting most of the cores while Alyssa and Olivier did most of the water sampling.  Perhaps the most striking feature of the lagoon was the extremely sulfidic water found below the surface mixed layer.  The general sediment pattern was to recover something in the range of 75cm to 1m in length, with anywhere from nothing to about the lower 1/3 of the material consisting of fine grained laminated carbonate that appeared authigenic, with the upper 2/3 consisting of intermittently laminated gytcha.  Water column investigations revealed a high abundance of photosynthetic organisms living at the very top of the oxygen depleted zone just below the halocline, a feature which owes its existence to the combined input of rainfall from above, seawater seeping in underground, and the resultant stratification of the water column.  Laboratory analyses of the sediments and water column samples will lead to a refined understanding of the hydrogen isotopic response to changing salinity, as well as a possibly improved understanding of the nature and scale of ITCZ migration.