Sampling the 2015/2016 El Niño event

Tonight, we boarded the Pirata and sailed to Isla Genovesa, where we will begin our sampling expedition to capture the 2015/2016 El Niño event.  Hopefully, if you’re reading this tomorrow morning, we are packing up our gear and beginning the arduous hike up to the island’s crater and down its walls to Genovesa crater lake.

Team Niño on the Pirata: Lenin  (el marinero), Stephan Hlohowskyj, Dr. Frazer Matthews-Bird, Dr. Diane Thompson (el hefe), Lenin (el capitan).  Not pictured: my many other great collaborators on this project– Dr. Jessica Conroy,  Dr. Jonathan Overpeck, Dr. Julia Cole, Dr. Mark Bush, Dr. Melanie Riedinger-Whitmore, Dr. Miriam Kannan, Dr. Aaron Collins

My colleagues and I have been monitoring the local climate and lake conditions of both Genovesa and Bainbridge crater lakes for the past 6 years.  These lakes are unique among the Galapagos islands, as connections to the sea have maintained vibrant lake ecosystems among a very hostile and dry volcanic landscape.  These lakes cook under the hot tropical sun and low rainfall, concentrating the lake to about 5 times that of the local seawater and creating a warm, very productive ecosystem. These local oases support a vibrant population of marine birds, including boobies, frigates and flamingos.

Great Frigate bird male at Genovesa crater lake.  Photo credit: Stephan Hlohowskyj

Red Footed Booby, Genovesa crater lake. Photo credit: Stephan Hlohowskyj
Great frigate male displays his stuff at Genovesa. Photo credit: Diane Thompson

Flamingoes at Bainbridge crater lake. Photo credit: Stephan Hlohowsky
But we are more interested in what lies beneath the surface: the sediments accumulating at the bottom of these lakes.  As the local climate changes, now and in the past, so does the type of sediments accumulating on the lake bottom.  Cores of sediment have been collected from these lakes, and these cores show a rich history of climate changes that have been captured in their layers. 
Jessica Conroy samples a sediment core in October 2012. Photo credit: Diane Thompson

Close up of a sediment core from Genovesa crater lake, showing the distinct layers of sediment.  Photo credit: Diane Thompson
But what do these layers tell us?  Because these very saline lakes are very sensitive to changes in rainfall, they have captured past El Niño events (and their dry, cold water counterparts La Niñas). 
For example, the sediment record from Bainbridge has been used to study the frequency of El Niño events over the past 6000 years.  The sediments accumulating at the bottom of this lake may therefore be key to understanding how the frequency of El Niño events has changed in the past and what may have driven these changes in El Niño frequency.  In turn, this will improve our understanding of how the frequency of these events may change in the future as our global climate continues to warm.
Despite the importance of these Galapagos lake sediment archives to our understanding of El Niño variability, there is a lot we still have to learn about these lakes to properly interpret the story told within their layers.  
To improve our ability to interpret climate story from these lakes, we have been monitoring the local climate and lake conditions while simultaneously collecting all of the sediments falling in the lake in simple sediment traps.  This allows us to better understand how changes in climate affect the physical and chemical characteristics of the lake, and how that in turn changes the type of sediments falling to the lake bottom.
Collecting the Bainbridge sediment trap samples in 2012. Productive lake.  mmmm productive!  Photo credit: Diane Thompson
We have been monitoring these lakes since December of 2009, a period that covers more than 5 full seasonal cycles and includes a weak El Niño, a moderate El Niño and sustained La Niña conditions.  However, we have yet to capture the effect of a strong El Niño on these lakes, which is key to studying El Niño events in the past.

Over the next 4 days, we will collect and redeploy our instruments at these two lakes so that we can measure the fingerprint of the 2015/2016 El Niño in Genovesa and Bainbridge crater lakes.

This material is based upon work supported by the National Science Foundation under Grant Number (NSF AGS-1561121). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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