Hunter HughesWhen many think of the typical scientist, they often imagine someone working in a sterile, isolated environment, devoid of human contact, perhaps pensively examining the neon-colored contents of an Erlenmeyer flask as they ponder the intricacies of the mundane and absurd alike. Even today, popular culture can’t seem to shake the decades-old stereotype of a scientist as a socially inept eccentric who must remind you of their brilliance with the frequent use of inaccessible scientific jargon. What many do not imagine when they think of a scientist is the kind that I have chiefly interacted with over the course of my career – adventurous problem solvers who scale frozen glaciers and delve into ancient forests to unravel the mysteries of the natural world. Far from an isolationist experience, this kind of science requires large groups of individuals with a variety of talents, working in tandem to avert danger and gather precious information that can help answer fundamental questions about the world we live in. Working in such groups is an exhilarating experience full of laughter, hard work, intense focus, and a healthy amount of banter using all of the colorful variations of language that the majority of people are familiar with (and, of course, an obligatory smattering of scientific jargon).
The quite literally down-to-earth group of scientists I refer to here (although they come in many varieties) are known as paleoclimatologists – a subset of geologists and marine scientists who study earth’s climate history in hopes of better understanding the future. Depending on their expertise, paleoclimatologists can find themselves from the deepest (sub)tropical jungles to the most frigid polar ice caps; from the lightless ocean bottom to the highest alpine peaks. That’s because, despite the fact that Earth’s climate is felt everywhere on its surface, there are relatively fewer places where the climate leaves a clear fingerprint that is both interpretable and generalizable – places where local changes in climate reflect larger changes in the global atmosphere-ocean system. Oftentimes, paleoclimatologists look for these elusive fingerprints in the rock record, where clues to Earth’s ancient climates lay entombed as variations in the natural landscape. The specific place where a paleoclimatologist might search for information about past climates is called a paleoclimate archive, such as ice cores or tree rings. The specific climate signal within that archive is referred to as a proxy, which can manifest as variations in the physical, chemical, or biological properties of that archive (see figure below).
From February 28th to March 6th of this year, I had the pleasure of joining a group of just such paleoclimatologists for their second expedition to the southern Caribbean island of Curaçao, just 40 miles north of Venezuela. Home to a vibrant confluence of cultures, Curaçao also stands as one of those rare locations that records important aspects of the Earth’s climate. Although exceptionally dry given its location, rainfall on Curaçao varies widely from year-to-year due to the El Niño Southern Oscillation, or ENSO, the largest natural climate pattern on the planet beyond the seasons. Therefore, the team of paleoclimatologists led by Dr. Isaiah Bolden (Georgia Tech) and Dr. Jessica Oster (Vanderbilt), were looking for evidence of the island’s climate past in two different archives. The first climate archive lay in stalagmites (or ‘stals’ for short), pillars of limestone rising from the ground throughout the island’s many caves. The second climate archive would be found in corals, clinging to the fringes of the island as it juts upward from the deep ocean. Together, these two disparate features of the island could elucidate thousands of years of climate variability related to ENSO. As the world reels in the midst of a severe ENSO event, the findings from this “Caves and Corals of Curaçao” expedition could prove vital in predicting ENSO variability in the coming century.
The stals and corals of Curaçao share many common features in the context of paleoclimatology. Both are made of the same base material (limestone), and both record aspects of the climate through changes in the chemistry of that base material. However, stals are nonliving features that form as rainwater seeps through the ground above a cave, dissolving and transporting limestone along the way. When that limestone-rich rainwater drips from the ceiling of a cave, some of the limestone accumulates on the ceiling, forming a stalactite. The remaining limestone remains with the drip water as it splashes onto the ground, forming a stalagmite. The chemistry of the limestone in those stals (specifically the oxygen isotopes) reflects many important aspects of the climate, like air temperature, rainfall, and even global ice volume. With the caves on Curaçao ranging over 100,000 years old, the stals within those caves could contain climate information pertaining to the coming and going of ice ages. For this reason, Dr. Oster has been running experiments for over a year to ensure that cave conditions are just right for capturing climate signals. Such cave monitoring efforts are vital for the success of any stalagmite paleoclimate study… and often involve squeezing into some pretty tight spaces.
The corals of Curaçao are ancient in their own right. In fact, the very bedrock of the island is composed of kilometers of coral reef, built over millions of years and exposed when sea level fell over 100,000 years ago. However, individual coral
colonies typically live on timescales of decades to centuries. Analogous to trees in many ways, a coral colony (which is only living at the very surface) creates annual growth bands like the
earlywood and latewood of tree rings. Growing between 3 and 20 mm per year, corals offer continuous, highly detailed glimpses of earth’s climate from decadal to centennial timescales. The changes in their skeletal chemistry have been attributed to changes in sea surface temperatures, salinity, pH, and terrestrial runoff or upwelling events. However, choosing the right coral for a paleoclimate study is extremely important, both for the scientific impact as well as for the sake of the coral itself. Corals are a keystone species for the vital coral reef ecosystem, which supports more than a quarter of ocean biodiversity and provides hundreds of billions of dollars of ecosystem services to the global economy. Therefore, any studies that involve collecting samples from a coral reef must be done with the utmost care and attention, in consideration both of the wildlife that call the reef home, as well as local residents of Curaçao that depend on those reefs for their livelihood.
With years of planning culminating in a single week in Curaçao, our team of paleoclimatologists worked frantically alongside local residents to collect the cave and coral samples we excitedly sought. The cave team scoured the island’s hidden and commercial caves alike, collecting drip water, fossils, and precious stalagmites. Meanwhile, beneath the waves, the coral team donned their scuba gear and continued coring a century-old massive starlet coral near the southern tip of the island. The expedition was a huge success, with surprisingly little unexpected setbacks that can lay waste to even the best-laid plans. Together, the caves and corals we collected from Curaçao could paint a sweeping and detailed picture of Earth’s climate past. The stalagmites, built from rain-weathered rock over thousands of years, will show slow-yet-large shifts in temperature and precipitation as the globe emerged from the last ice age. On this multi-millennial scale timeline, the corals will give us highly detailed windows into seasonal variability over decades to centuries, contextualizing the broader climate signal into timescales relevant to a single human lifetime.
It was a great privilege to work alongside such dedicated, talented, and good-hearted people as those whom I accompanied in Curaçao just a few short weeks ago, most of whom I’d only just met. Great friendships have been forged out of much less. And as I reflect upon the impact that this expedition had on me, I can’t help but wonder if this crucial aspect is what pop culture has been missing from their typecasting of scientists. While scientific inquiry and ‘the pursuit of Truth’ may bring many people into the sciences, it is often not enough to keep us there. Instead, it is the people, and the relationships with them that we forge along the way, that drive us to reach further than we ever could have in isolation.
Peer Editor: Elissavet Chartampila