Tuesday, November 24, 2015

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.

Monday, November 23, 2015

First Glimpse of the 2015 El Niño from in the trenches

If anyone asked me prior to this trip what I expected to find in the Galapagos during this strong El Niño event-- an event that may be on par with the strongest events in the historical record (in 1982-83 and 1997-98)-- I likely would have given a textbook answer of what happens in the Galapagos during a “classic” strong El Niño event.  It would have sounded a bit like this: rain, lots of rain; warn waters; dead sea life; dry, barren landscapes transformed to lush green wonderlands full of fat, happy finches.
Photo by Stephan Hlohowskyj
This picture I had painted in my head came not just from research on El Niño, but also from personal accounts of colleagues who were in the Galapagos during the huge 1982-83 El Niño, which hit the Galapagos very hard.  I heard stories of sea lions dying on the beaches while land birds thrived off of the unusually lush landscape.   Local divers and reef experts also paint a stark picture of the coral reefs, which succumbed to coral bleaching and death as a result of the high ocean temperatures.  Even 30 years after this event, its devastating impact was impossible to ignore while collecting coral samples on our last 2 expeditions.  We were hard pressed to find any large coral heads that survived that event, and all of the corals we sampled had a distinct death band in 82/83.

During these large, classic El Niño events, marine ecosystems crash around the Galapagos and throughout the eastern Pacific Ocean as a result of above average temperatures and a reduced influx of key nutrients from deeper waters.  At the same time, terrestrial ecosystems thrive under above normal rainfall.
The day before we departed for our trip, the Ecuadorian Government declared a “state of emergency due to the phenomenon of El Niño.”  The announcement said that the Ecuadorian Government was forecasting a stronger than normal event with unusually high volume of rainfall, and encouraged residents and visitors to visit their new website to learn about El Niño and its effects on Ecuador.
As an early career scientist who has focused her research largely on the phenomenon of El Niño—aiming to improve our understanding of how the strength and frequency of these events has changed in the past and may change in the future—I was extremely excited to get on the ground to see and measure these impacts in real time. 
So you can imagine my disappointment when I got here to find that the El Niño picture I had painted in my mind was, well only a fairy tale?!  Well, no, but where was all of the rain??
The clouds had definitely rolled in, with ominous clouds above us as we quickly devoured the coveted “encocado de pescado” at Williams, our favorite restaurant on the island.

And the view out of the back porch of our dorms at the Charles Darwin Research Station is no doubt more cloudy every day 

than it was during our last trip in January of 2015 (around the peak of last year’s warm/wet season)

But despite the ominous clouds, it has not rained.  Our boat captain Lenin tells us it rained a few days ago, but made a point of saying that he is skeptical of this El Niño.  He doesn’t believe the hype, and thinks the government’s state of emergency is just a control tactic. 
BUT, on the other hand he notes that the guides have told him that Darwin and Wolf (the most northern Galapagos Islands) are very lush and have been receiving a lot of rain.  So are the northern islands being impacted more by this event so far, despite warm ocean temperatures throughout the islands? This surprising observation has my head reeling through open questions and implications. 

How patchy are the El Niño rains among the islands?   And as a result of this patchiness, could such a large event be missed if only sampled from one island?  What are the implications of this for the interpretation of the frequency of El Niño events in the past from natural archives of past climate (e.g. sediments accumulating at the bottom of Galapagos lakes)? 
I anxiously await our field expedition to Genovesa and Bainbridge crater lakes to try to address these open questions.  We have been monitoring the local climate and lake conditions at these sites to determine how such El Niño events are recorded in these lakes; for example, how much rain falls during El Niño events, and how does this change the conditions of the lake and the sediments deposited on the lake bottom? 

Based on the occurrence of these signature El Niño layers in sediment cores extracted from these lakes, we can then produce improved records of the frequency of El Niño events over the past 6,000+ years.
And now as I finish writing this, it just started raining!!! Stay tuned…to be continued…

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.