A Smiling Rain God

by Jess Conroy
With the departure of our fearless leader, it’s my turn to blog from the field.  I was lucky enough to join in on this coral collecting trip to help out and to pursue my own research agenda. As a postdoc in Kim’s lab, the project I’ve developed is based on collecting seawater and rainwaters from across the tropical Pacific. I will be measuring the chemistry of these water samples--specifically, how the isotopic values of hydrogen and oxygen change over time. These numbers are fascinating, and can tell us a whole lot about the hydrologic cycle in this part of the world. For example, at Christmas, changes in these values can tell us whether it’s been wet or dry, or if ocean water is sloshing in from the west of the island—changes that are today most often linked to El Nino and La Nina. More importantly, what these water isotopes are saying is recorded by the local corals. The geochemical message embedded in coral skeletons is one way coral paleoclimatologists like Kim, Diane, and Hussein reconstruct past climate change.

Here I am taking a seawater sample in the yard of Dive Kiribati,
our home on Christmas Island.

So you can imagine then it’s really important to understand just how these isotopic values in rain and ocean water vary, and how they relate to modern climate measurements, like ocean salinity or rainfall amount. Trouble is, there are hardly any of these measurements available from this part of the world. Yikes!  My research is a major attempt to start plugging this hole between paleoclimate isotope records and modern climate data.

As Kim and crew have struggled with the drill, my progress in the field has been pretty seamless. I braved the rats and rat turds in the fuse box, and got the weather station up and running.  I set up my rain collector, and I’ve been taking lots of seawater and rainfall samples.  It’s normally pretty dry here, but apparently my [Sailor Jerry/sunstroke-induced] rain dance was effective: it has rained everyday we’ve been on the island, providing me with lots more data points than I expected. Another bonus: there is no sweeter relief after hours of hot fossil coral hunting than a gentle Pacific rain shower.

However, storms have also led to swelling seas, and swelling stomach contents, so not everything has been perfect. And I completely fumbled my first attempt at sampling rain waters through a single rain event. I frantically started to get my sampling materials together one afternoon as it started pouring, but without a stopwatch of any sort on hand (my cheapo sport watch oddly stopped working just as we crossed the dateline), I forgot to time the rate of drips off the roof. Thus, I collected a lot of water samples without any quantitative idea of how much it rained. I feel only marginally better that on the last Borneo expedition, they forgot to do this too. Luckily I got to remedy this mistake yesterday, and hopefully I will get some more chances in the coming week, but stay tuned for more face palms.