Sunday, May 20, 2012

Billions and billions of corals

Liz Wiggins showing off her humongous fossil coral,
a mystery species that grows 1cm/yr. The piece she
found will likely yield 50 years of continuous record.
No idea when it grew, we'll have to wait for U/Th
radiometric dates to tell us. 
Sorry not to post for a few days. It takes forever with the internet connection we have, and we have been BUSY collecting corals.

Our mini-truck with rigged rain fly, providing much-needed
shade.
The last two days we've been over on the windward side of the island, called "Bay of Wrecks", scouting the 20km-long beach for fossil coral rubble like those pieces shown in the photo. The first day we took our rust-bucket mini-truck with no shade, rigging a rain fly over the back in a desperate attempt to get the team some shade (see photo). We near-wilted in the sun. Everyone got sunburned.

Day 2 we were a bit better prepared, both mentally and physically. Liz broke out the Southern Belle hat (see photo), so you know it was serious sun. We also had rented a huge truck with a pavilion over the back for the day, from a local named Mopuola, who turns out to have a BS from Tuvalu and speaks perfect English. I only found all this out *after* I had bungled my way through an elaborate mime routine to communicate my desire to rent his truck. What an idiot. My miming skills aren't really coming in handy here, most people speak fairly good English. For example, we had found some rather large Porites corals (our target of interest for paleoclimate reconstruction) in some of the village gardens. We went to bungle our way through a conversation, and found ourselves speaking with a bunch of English-proficient villagers. They were very curious what we were doing with their rocks, and some of them wanted them back after we poked holes in them. We tried to explain our purposes, things clicked a bit better when we said "El Nino", as their lives are at the mercy of the El Nino-Southern Oscillation extremes here. We will be giving some presentations in the local high schools tomorrow, to explain to them the uniquely valuable records that are strewn about their gardens, white gold to us. We will have to spend a fevered few days drilling the larger Porites heads we found scattered throughout the village. That haul will add to over 400 fossil coral samples we collected yesterday! We will definitely top 1000 on this trip.

Why do we need so many fossil corals, you might ask? For a couple reasons. One, we do not know when any of these corals grew, and we'd really like to have good coverage through some key intervals of time. One target is the so-called Medieval Climate Anomaly, roughly 1000 years ago, when mega-droughts ravaged the western United States, and parts of the mid- to high-latitude Northern Hemisphere were warmer than the rest of the millennium. Theory and models suggest that cooler-than-average tropical Pacific temperatures may have contributed to the global climate reorganization, but data in support of this hypothesis (including our original fossil coral reconstruction from nearby Palmyra Island) have been scant and oftentimes conflicting. Hussein will be targeting this interval for his dissertation research, yet we only have 2-3 sequences in our entire collection that date to this interval at present. Hopefully we can provide 10 or so more. The second reason for the over-the-top collection strategy is to make sure that we have multiple individuals from the same time interval, rather than just one or two. That is necessary because we have observed, along with many other coral paleofolk, that contemporaneous corals are offset from each other in oxygen isotopes (the "proxy" that we use to track past climate changes in the corals). We do not yet know why this is the case, but it being the case, we have to beat down that error with large numbers of corals, trusting that the average of many corals is a better estimate of past climate than any single individual.

And so we collect hundreds and hundreds of samples. I should say that this is not common practice in the field. We usually would be happy to publish a reconstruction with 5-10 samples over a given time period. My first paper contained 8 fossil coral sequences, and was considered over-the-top in terms of numbers of samples. The paper we are writing up right now, spanning the last 7 thousand years, will contain 15 sequences. The project we are launching with this fieldwork is designed to deliver hundreds of sequences for our next papers. A high-volume enterprise, for sure, and very expensive. Fingers crossed that NSF will eventually fund the lab component of our work!

For now, I'm off to breakfast and then a long day of diving. We'll target the usual suspect, Porites, as well as a living colony of the mystery species we collected so many of yesterday (pictured with Liz). It's a stunning day, light wind and sunny, so it should be pleasant out there.

Quote of the day:  "There is no 'I' in fieldwork." [Diane Thompson, pausing for a breather while hauling, together with 3 other people, a 200lb box of fossil coral across a football field-sized stretch of sand to the truck.]

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