Future El Niño

The El Niño weather pattern in the tropical Pacific influences weather across the planet. As the planet warms, it is unclear if El Niño will grow stronger, bringing more extreme floods and droughts to some regions, or if El Niño will slacken, creating more uniform weather. Scientists aboard the Lamont-Doherty ship, R/V Langseth, will sample ancient sediments from the central Pacific Ocean to see how El Niño and climate varied in the past, and how they may change again in the future.

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Location:
Line Islands, south of Hawaii
Team: Co-led by Lamont climate scientist Pratigya Polissar, Lamont graduate student Allison Jacobel
Purpose: Climate Research
Start Date: May 1, 2012

Women Making Waves

Posted By: Guest Blogger on June 11, 2012

By Allison Jacobel

In the seafaring lore of yore at least two statements have traditionally been held as fact: the more rum the more merry the mates and any and all women are bad luck. While the origin of the first statement is fairly obvious, the second may require a bit of explanation. In the times of ancient mariners it was held that not only were women incapable of doing physical work aboard a ship but also that they were a distraction to the men onboard.  Together these two factors were thought to produce a dangerous inattention to the sea which could anger the forces of nature and cause fearful storms and gales.

XBT_deployment

Samantha Bova (Brown University) prepares to deploy and XBT over the side of the R/V Langseth. XBTs are used to measure the temperature and salinity of the ocean.

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The female geoscientists aboard the Langseth.

Jean Lynch-Stieglitz in a teaching moment in front of the main lab console.

Christina King, Ashley Maloney, Allison Jacobel and Kate Wejnert getting ready to sample the CTD.

Fortunately (or perhaps unfortunately depending on how you feel about the first statement), we here on the Marcus G. Langseth are bucking the shackles of yore in the most dramatic of fashions.  On this cruise not only do we have women aboard but all ten of the graduate students and our post-doc are female[1]!

Aboard the Langseth are:

Sam Bova – Brown U., Ann Dunlea – Boston U., Heather Ford- U. of California, Jen Hertzberg- Texas A&M, Allison Jacobel – Columbia U., Christina King – U. of Rhode Island. Ashley Maloney – U. of Washington, Julia Shackford- Texas A&M, Kate Wejnert– Georgia Tech, Ruifeng Xie – Texas A&M.

While over the past 20 years, women have increasingly demonstrated their ability to compete in many sectors of the workforce, a slower trend has been observed in the geosciences than in any other STEM discipline except engineering. In 2004, 42% of the BA and BS degrees awarded in the geosciences were to women and only 34% of the PhDs awarded in the geosciences were to women[2].  Most troubling is that of full professors in US geosciences departments only 8% are women[2].

It will likely take more than one generation to overcome these trends, but many of us aboard the Langseth are optimistic.  While the driving forces and support networks behind the women on board are unique, several commonalities can be found.

I think most in the field would agree when I say we’re a well-awarded group and here I think credit is due to both government programs and private foundations for recognizing the need and opportunity to support young women in science.  While some might point to the demographics on board as a reason that the emphasis on supporting women in science is no longer needed, I think the scarcity of female professors in tenured positions at most universities is a clear argument that this emphasis should continue.

We also owe thanks to the pioneering female scientists who were instrumental in deconstructing many of the biases against women in science and who paved the way for our generation’s steps forward. For example we are fortunate enough to be led in our scientific mission by Jean Lynch-Stieglitz, one of our two chief scientists.  Jean was the first female professor in the Department of Earth and Environmental Sciences at Columbia University and holds amongst many accomplishments the 2000 receipt of a NSF CAREER Award in recognition of her role as an outstanding leader in both education and research.  Jean is currently a professor at Georgia Tech and last but certainly not least, mother of two.

Finally, I think some credit is due to the male scientists on board (and those PI’s back on land) who helped to bring us each aboard and who recognized our skills, drive and potential among a field of qualified candidates.  These men are neither intimidated by, nor resentful towards, the smart women aboard and have invested their time and academic resources into helping us all to become better scientists.

While the prevalence and acceptance of women in the geosciences is growing, we are also aware of the professional gaps left to be bridged, both in our own field and others.  I don’t take the opportunities I’ve been given for granted and believe I speak for the other women aboard when I say we hope to encourage other young women to pursue their interests in the sciences and other traditionally male-dominated fields. Through participation in professional societies, activities involving disadvantaged girls in schools, summer programs and more, we hope to make waves not only in the seas of the South Pacific but also in in the communities we call home.

For more information about women in the geosciences check out the NSF/AWG sponsored workshop proceeding “Where are the Women Geoscience Professors?”

Allison Jacobel is a graduate student at Columbia University who studies the past circulation of the ocean and atmosphere using the chemistry of deep ocean sediments.


[1] I should not neglect to mention that we are fortunate to have one male undergraduate on board, Victor Castro, who is a much-appreciated member of the scientific party.

[2] Holmes, M.A., O’Connell, S., Frey, C. & Ongley, L. Gender imbalance in US geoscience academia. Nature Geoscience 1, 148–148 (2008).


Lucky 13 Gets Us 250,000 Years of Sediment

Posted By: Pratigya Polissar on May 19, 2012

Beautiful white sediment inside the core barrel.

mud tatto

A mother’s day tattoo celebrates the good cores we are getting.

sediment cores

Rick Murray (Boston University), Victor Castro (University of California, Santa Cruz) and Samantha Bova (Brown University) discuss what the sediment’s color tells us about ocean chemistry

We have been steaming and searching for locations on the seafloor where the sediments are accumulating undisturbed. We tried without luck to take cores at several promising locations, however the cores came up less than perfect.  It turns out that much of the undersea portion of the Line Islands has ocean currents that remove and erode sediment. This erosion shows up in the sediment cores as sandy layers where the very small grains of sediment have been swept away. So, we kept up our vigil in the main lab area, closely monitoring the seafloor for small pockets of sediment that looked promising. Some pockets are only a few tenths of a mile across while others are a mile or two. Many that look beautiful from a distance turn out to be ugly on closer inspection.

On our 13th core attempt of the cruise, we got lucky. The corer came back full of the beautiful, white mud. The 20-foot core contains over 250,000 years of sediment and spans the last three glacial cycles in earth’s history. During each of these cycles the earth cooled and large ice sheets expanded over North America and elsewhere. In our core, these cycles are indicated by color changes from greenish brown to white and back.

After lucky 13, we began to hone our strategy and are finding more locations with good sediments. We now have lucky 15, 17, and many more; we now have over 30 cores and counting. Not all of them are perfect, but we are getting better at finding good sediments and faster at coring them.

sediment analysis with multi-sensor track

Ann Dunlea (Boston University) uses a multi-sensor track to analyze a sediment core aboard the R/V Langseth.

sniffing sediment for hydrogen sulfide gas

Mitch Lyle (Texas A&M University) sniffs a new sediment core for whiffs of hydrogen sulfide gas. Decomposition of dead algae in the sediments helps produce the gas.

tropical sunset

A beautiful tropical sunset provides an excuse to relax.

A Rare Treat – The Green Flash

Posted By: Guest Blogger on May 15, 2012

By Lee Dortzbach,

light dispersion through a prism

Refraction through a prism separates light into different colors. The atmosphere has the same effect, separating the sun’s image into the ROYGBIV colors (red, orange, yellow, blue, green, indigo, violet). The sun’s green image is visible during the sunset when the brighter orange and yellow images fall below the horizon. Image courtesy of D-Kuru/Wikimedia Commons licensed under the Creative Commons Attribution-Share Alike 3.0 Austria.

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Enlarged view showing the green at the edge of the sun’s disc. Photo by Tatiana Moreno, a protected species observer on our cruise.

I work as the Chief Mate aboard the Research Vessel Marcus G. Langseth for this cruise and stand the 4 to 8 watch.  Every morning as I get the ship where the scientists need to be, I watch for the sun to rise.  Every evening I watch for it to set.  There are some days when clouds are around and make for some great sunsets.  Other days we cannot see the sun through all the clouds.

Sunday night after successfully recovering a gravity core about 42 miles north of the equator, conditions were right for a rare treat – the green flash.  There were clear skies around the Sun, good visibility and a clear horizon.  When I first heard about the green flash, I thought it was something that was noticeable and quick.  Over the last decade, I have seen that it is not a sky-covering flash (as depicted in the recent Pirates of the Caribbean: At World’s End), but a short lived change of the sun’s light as it sets.

It happens because of refraction of light through the Earth’s atmosphere.  The white light of the sun is broken into different wavelengths of visible light we recognize as different colors.  The red and orange cover most of the sky, the yellow of the sun gets more orange-like as the sun sets and the blue and violet get scattered too much for us to see.

So what about the green?  It too is scattered most of the time until the tip of the Sun is barely visible above the horizon.  The Sun’s yellow light is refracted more and so the ‘yellow’ sun sets below the horizon before the ‘green’ sun.  The sliver of green becomes visible to our eyes only when the bright yellow light is fading during the sunset.  It starts from the bottom up in a horizontal band that grows a little taller as the sun sets.  On a few occasions I have seen a sliver of blue/violet light below the green (a challenge against a blue ocean and a greater treat).  In the latitude of the United States, it lasts about 0.7 seconds.  Sometimes it can last up to 4 seconds.  Ours lasted between 1 and 2 seconds.  Definitely a flash compared to the core we just recovered!

For more information and other pictures of green flashes, click here.

Lee Dortzbach graduated from the U.S. Merchant Marine Academy with a B.S. in Marine Transportation in 2000. He has been around the world on several different ships over the last decade, including two oceanographic research vessels. He lives in landlocked Utah.

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Beginning of Sunday’s green flash. Photo by Tatiana Moreno.

MGL_1208_Green_Flash_Middle

More green visible as the sun sets. Photo by Tatiana Moreno.

Drilling Ancient Mud from Seafloor No Easy Task

Posted By: Pratigya Polissar on May 09, 2012
A sediment core is secured along the ship’s rail for sampling.

A sediment core is secured along the ship’s rail for sampling.

Watching winch tension as a core is pulled out of the seafloor.

Scientists monitor how hard the cable is pulling as a sediment core is pulled out of the seafloor. Too much pull will stretch the cable and could cause it to break, leaving the sediment corer on the bottom of the ocean.

Yesterday we left our first study region with new samples from the seafloor and a healthy respect for the ocean currents that can erode sediment deep in the ocean.  The samples will be useful for our research but we had to work for them.  The seafloor we surveyed was heavily eroded and we had to look carefully before finding sites that were promising enough to sample.  Even then we ran into difficulties getting the sediments back to the ship.

We spent several days surveying the seafloor using instruments on the ship to identify possible sites for sampling.  We looked for flat areas where we could see layers of sediment below the seafloor.  These layers show up in the echoes from sound pulses in a type of measurement called seismic reflection (see previous blog post).  Unfortunately much of the region we surveyed has deep gullies with no sediment layers.  Ocean currents have scoured these regions leaving no sediment for us to core.  We finally located several small areas that had a hint of sediments and one big pile of sediment we thought would be our best chance for samples.

We use a sediment corer to take samples of the seafloor.  The corer is a long tube with heavy weights on top that push the tube down into the seafloor.  When the tube is pulled out it removes a long cylinder of sediment that we bring back to the surface.  The corer is lowered on a steel cable at about 1.5 miles per hour and takes more than an hour to reach the seafloor.  At 150 feet above the seafloor, a mechanical trigger releases the corer from the cable and 5,000 pounds of steel rocket towards the bottom.  The weight and speed push the corer up to 30 feet into the sediments.  Then we have to pull the corer back out.  Sometimes this is easy but if the sediments stick to the corer it can take almost 20,000 pounds of pull to free the tube and slide it out.

Section of sediment core

A section of sediment core showing changes from clay sediments at the bottom to sandy sediment on top.

Sorting foraminifera shells

Foraminifera shells a few millimeters across can be sorted with a fine-tipped paintbrush. The different species of foraminifera can be used to determine the age of the sediments.

The other important step in coring is to keep the sediments inside the tube on their two-mile trip back to the surface.  This seems obvious but we ran into troubles with the very first core we took.  Usually a ring of metal fingers in the bottom of the core (called a core catcher) keeps the sediment inside the tube.  However, the sediment we were coring contained a lot of sand-sized shells that was washing out of the tube leaving us with no sediment by the time the corer reached the surface.  To prevent this, we added a sock of fabric around the core catcher to keep the sand from washing out.  Bingo!  The fabric kept the sand in the corer and we started recovering sediments to study.

When the sediment corer arrives at the ocean surface it is laid horizontally along the ship’s rail where we take a sample of the sediment in the core catcher to determine the age of the bottom of the core.  This age is determined by looking for a striking, pink colored shell made by a type of plankton called foraminifera. This pink foraminifera was abundant in the Pacific Ocean until 120,000 years ago, so if we find pink shells we know the sediments are at least 120,000 years old.  We will do more detailed analyses later but this age gives us our first peek at how much time it took for the sediments to accumulate.

Next, we cut the core into smaller sections that are easier to handle and the core is split open so we can see how the sediment looks.  We study its color, texture and composition before storing it in a refrigerated container aboard the ship.  At the end of the cruise we will send the container to the Deep-Sea Core Repository at Lamont-Doherty Earth Observatory where the sediments will be preserved for researchers around the world to study.

We are now steaming south to the equator to start a new survey to find the right locations to drill more sediment cores.

Sock inside the core catcher

Katherine Wejnert from The Georgia Institute of Technology samples the sock inside the core catcher.

Cutting a sediment core into sections.

Steve Hovan (Indiana University of Pennsylvania) and Allison Jacobel (Columbia University) cut a sediment core into sections.

Preparing to take notes on the sediment composition.

Christine King (University of Rhode Island) prepares to take notes about a new sediment core.

Microscopic examination of sediments

Jennifer Hertzberg (Texas A & M University) determines how old the sediments are by looking for a pink-shelled species of foraminifera that lived in the Pacific Ocean 120,000 years ago.

Through the Looking Glass: Peering Through the Bottom of the Ocean

Posted By: Pratigya Polissar on May 06, 2012
Learning about how to take sediment cores.

Scientists aboard the R/V Langseth learn how to prepare sediment core tubes before they are lowered to the bottom of the ocean.

Sunset over the tropical Pacific Ocean. Deep below the waves, large mountains rise up above the seafloor.

Scientists monitor the echoes as they stream into the main lab aboard the R/V Langseth.

We are in the fifth day of our research cruise to the Line Islands and shipboard life is beginning to settle into a routine.  Most people have their ‘sea legs’ and our sleep schedules are adjusting to the midnight to noon or noon to midnight work shifts.  Meals are a time to catch up with scientist and crew, and the motivated scientists have begun regular exercise schedules in the ship’s gym.

As we steam over the incredibly wide expanse of the Pacific Ocean, the waves seem endless and monotonous, and the wind blows steadily from the same direction for days on end.  However, beneath us the seafloor is far from monotonous. Huge mountains rise 10,000 feet above the seafloor and create escarpments, ridges and valleys that would rival the peaks of the Rocky Mountains.  It is along these mountains that we hope to find sediment for our research.

Using scientific instruments we peer ‘through the looking glass’ to learn what the seafloor and sediments look like.  The analogy to the looking glass is apt: Alice stepped through the mirror to see the world beyond and we peer through the bottom of the ocean to see what is below.  However, unlike Alice, we use our ears.  Short pulses of sound from the ship are focused on the seafloor and we listen to the echo and reverberations that return to the ship.  Depending upon the pitch and intensity of the sound we can look at the top layer of the sediment or much deeper.

Sound pulses echo off the seafloor and are detected by our ship. The time it takes the pulses to return tells us how deep the seafloor and sediment layers are below the surface.

The most basic echo we listen to comes from the very top of the sediments.  This echo travels down through ocean, bounces off the top of the sediments and returns back to the ship.  We measure the time it takes to go down and come back up, and knowing how fast sound travels through seawater (~one mile per second or 3,400 miles per hour!) we can determine the distance to the bottom of the ocean.  The times are very short, about two seconds for water a mile deep.  We use these distances to construct a detailed map of the bottom of the ocean.  This map shows the mountains and valleys on the seafloor where we will take our sediment samples.  We also listen to how loud the echo is when it comes back to the ship.  Hard surfaces like rock have a loud echo while soft sediment gives a quiet echo.  This is an additional way to determine where there are ocean sediments to sample.

If we turn up the sound volume and use a lower pitch we can look beyond the seafloor into the sediments below.  Now rather than just one echo from the seafloor, we begin to hear many echos as sound reflects off the different layers in the sediments.  These echos allow us peer beneath the seafloor to know how thick the sediment is and whether it is nicely layered or jumbled and distorted.

When we find the right sediments—not too deep, smooth, with nice layers—we will take cores of the sediment to study the climate history preserved in the layers.

Side-looking map of Kingman Reef (part of the Line Islands) and the surrounding seamounts and valleys (colors indicate the depth of the seafloor, 5000 meters is over three miles). Robert Pockalny, a geophysicist from the University of Rhode Island, constructed this map from depths determined by sound pulses that echo off the sediment.

Why I Care About the Bottom of the Ocean

Posted By: Pratigya Polissar on April 30, 2012

R/V Marcus G. Langseth docked in Honolulu, HI

R/V Marcus G. Langseth docked in Honolulu, Hawaii.

It is the middle of the night and I am wide awake thinking about the ocean, specifically the bottom of the ocean.  Is it rocky? Jumbled?  Smooth?  I am wondering this because I want to take samples of the seafloor to study.  Rocky is bad.  Jumbled is bad.  Smooth is good.

In one of my favorite New Yorker cartoons a woman says, “I don’t know why I don’t care about the bottom of the ocean, but I don’t.”  Well, for the next four weeks our research group will care a lot about the bottom of the ocean.  We are sailing to the middle of the Pacific Ocean where we hope to collect sediment to study how climate has changed in the past.  Our destination is a group of atolls and seamounts collectively known as the Line Islands.  They include Kingman Reef (U.S.A.), Palmyra Atoll (U.S.A.) and part of the island nation of Kiribati.

The ocean around the Line Islands is over two and a half miles deep (4 km)—too deep to preserve the climate changes we want to study.  So, we are going to take sediment cores on the flanks of the islands where the sediments are better preserved.  The flanks are also where a lot can happen to the sediments.  Slumps can break off huge chunks of sediment, ocean currents can erode the sediment and slumps from higher up the flank can deposit thick layers of sediment.  All of these happenings alter or erase the regular ordering of the sediment (the stratigraphy in geologists terms) and make them unusable for our research.  So, I am thinking about the bottom of the ocean.

Map showing the first part of our cruise aboard the Langseth. The shaded colors show the depth of the ocean (bathymetry) in meters. The red line shows where we will be heading in the next few days.

Our group is sailing on the research vessel (R/V) Marcus G. Langseth, an oceanographic research vessel operated by Lamont-Doherty Earth Observatory (where I work).  The ship is a floating scientific laboratory, with the ability to study and take samples of the ocean water and sediments wherever we go.  The scientists on board include seventeen researchers from nine institutions.  In addition, there are 34 technicians and sailors who make sure the ship and scientific instruments are functioning properly so we can collect the data we need.  The moment we leave the dock in Hawaii will be the culmination of almost a year of planning, a lot of hard work by the crew of the Langseth, and financial support from the U.S. National Science Foundation.

Our goal for this cruise is to collect cores of deep ocean sediment that we can use to study the past behavior of El Niño as well as the climate of the tropical Pacific Ocean.  Although our studies focus on the Pacific Ocean, the results could tell us about many different areas of the globe. El Niño weather affects regions as far apart as Indonesia and New York State.  In fact, El Niño events are responsible for the largest year-to-year changes in global weather.  Our goal is to learn how El Niño has varied in the past so that we can develop better forecasts for the future of El Niño into the 21st century and beyond.

Over the next four weeks I will be writing a series of articles about our cruise.  Topics will include El Niño, life aboard the ship and how we actually collect water and sediment samples from the ocean. Stay tuned!

In the meantime you can track where we are online.