by Jenny Marder //VANDENBERG SPACE FORCE BASE, CALIFORNIA//
It’s less than four days before the planned launch of Landsat 9, and the perfect time to learn about this amazing satellite and the nearly 50-year-old Landsat program. Did you know:
Landsat gives us the longest continuous space-based record of planet Earth.
Since the first satellite launched in July 1972, the mission’s eight satellites provide five decades of information about our planet’s land and atmosphere. And they show us how our planet is changing. This will continue with the Landsat 9 launch, providing more data and higher imaging capacity than past Landsats.
Landsat 9 will carry two science instruments …
The Operational Land Imager 2, or OLI-2, sees at a spatial resolution of 49 feet for its panchromatic band, which is sensitive to a wide range of wavelengths of light, and 98 feet for the other multispectral bands. Its image swath is 115 miles wide, with enough resolution to distinguish land cover features like urban centers, farms and forests.
The Thermal Infrared Sensor 2, also known as TIRS-2, measures land surface temperature in two thermal infrared bands using principles of quantum physics to measure emissions of infrared energy.
… and it will orbit the Earth at an altitude of 438 miles.
That’s roughly the distance between Dallas and Memphis.
Landsat has shown us how dynamic the planet is in response to human activities.
“When you grow up in an area, you don’t really notice the changes that occur over years and decades,” Dr. Jeff Masek, NASA Goddard’s Landsat 9 Project Scientist, told Dr. Alok Patel in December 2020 for PBS’s NOVA Now podcast. “But when you run the movie in fast motion, suddenly we see all these changes: urbanization and changes in forest management, areas where agricultural irrigation suddenly goes into desert environments.”
Watch this video for a Landsat roadtrip through time.
You’ll learn about the first game-changing launches in the 1970s, the advent of natural color composite images in the 1980s, the increased global coverage in the 1990s, the move to free and open data archives in the 2000s, the modern era of Landsat observations in the 2010s, and now, the launch of Landsat 9 in 2021.
And follow us here and on Twitter @NASAExpeditions this week as we count down to Landsat 9’s launch!
By Emily Fischer, NASA’s Earth Science News Team /GREENBELT, MARYLAND/
On July 7, 2021, NASA sent two robotic explorers to the Arctic to collect sea surface temperature data and improve estimates of ocean temperatures in that region. Pairing up with Saildrone, a designer and manufacturer of non-crewed surface vehicles or USVs, researchers hope to use the results to better understand the impacts of climate change in the Arctic.
“The Arctic is one of those regions that’s being very rapidly impacted by climate change,” said principal investigator Chelle Gentemann, a senior scientist at Farallon Institute in Petaluma, California. “We’re all connected, so what happens in Siberia is going to affect what happens in California. And one of the keys to understanding and mitigating climate change is understanding what’s going on in the Arctic, how fast it’s changing, and how it’s going to affect future weather.”
Acting like Earth’s refrigerator, Arctic climate and weather interact with the rest of the world. Over the past 30 years, the Arctic has warmed about twice as fast as the rest of the Earth. This type of warming can influence sea level rise, global ocean currents, and natural hazards like hurricanes. Researchers in the Arctic are investigating recent and past changes and how they influence other parts of the planet.
The Arctic is challenging to study because of its frigid tundra and sea ice dynamics. For years, climate researchers have relied on satellite remote sensing to measure key ocean properties, including ocean salinity, ocean temperature and air-sea interactions (for example, hurricanes). Satellite measurements are validated by collecting field data using buoys and research vessels. Yet in the Arctic, buoys are often destroyed by shifting ice and research vessels are expensive to operate.
“The problem is that almost all of our buoys are located along the coasts of the United States, Europe, near India and Asia and along the tropics. We aren’t able to deploy and maintain buoys in the Arctic,” Gentemann said. “We have to rely on satellite data to understand Arctic ocean temperatures and how they’re changing with climate change.”
Saildrone USVs, are autonomous sailboat-like vehicles powered by green technology; they are propelled by wind and use solar-powered sensors. These autonomous vehicles can be steered from computers hundreds of miles away, allowing them to access severe ocean environments, like the centers of hurricanes and shifting packs of sea ice in the Arctic. They provide a resilient and affordable means to validate satellite data and develop and improve algorithms that model changing temperatures.
The 2021 NASA Arctic Cruise is ongoing; the Saildrone USVs passed through the Bering Strait and are headed into the Chukchi Sea. In previous Saildrone missions, NASA researchers found close correlation between satellite remote sensing measurements of sea surface salinity and data collected by Saildrone.
“We have confidence in satellite information because we are also seeing similar things in the on-site measurements collected by Saildrone. This is encouraging. This tells you that we can use the satellite data to monitor what’s happening over these long periods of time,” said Jorge Vazquez, a scientist for NASA’s Physical Oceanography Distributed Active Archive Center, or PO.DAAC. PO.DAAC is one of several NASA Distributed Active Archive Centers, which process, archive and distribute data collected from NASA projects.
The primary focus of the 2021 NASA Arctic Cruise is to validate sea surface temperature data from satellites, but scientists have also collected information on air-sea interactions, ocean stratification (different layers of water), ocean currents, sea surface salinity and the marginal ice zone (an area where ice forms seasonally and varies over an area) to answer other scientific questions.
The 2021 NASA Arctic Cruise is part the Multi-Sensor Improved Sea Surface Temperature project, or MISST. This is an international and inter-agency collaboration aimed at improving weather and climate research and prediction by providing better-quality ocean temperature measurements from satellites. NASA satellites aid in this effort, and projects like the 2021 NASA Arctic Cruise validate NASA satellite measurements to further MISST’s mission.
“What we’re finding is that we live on a planet where you have to have a multidisciplinary and international approach to understand how this planet works. It’s a team effort,” Vazquez said.
NASA has an open data policy, and the 2021 NASA Arctic Cruise takes this one step further. The project has an open invitation for other researchers from around the world to be an observer on the mission, have access to near-real time data and participate in the conversation about the mission and science objectives. The Saildrone Arctic deployments are available through the PO.DAAC at http://podaac.jpl.nasa.gov.
By Rei Ueyama, NASA Ames Research Center /SALINA, KANSAS/
It’s 3 a.m. in Salina, Kansas. The moon is out. Crickets are chirping on this balmy summer night. The light above the door to the hangar softly illuminates the sign that reads “DCOTSS.” Most teammates are just waking up. I unlock the door and walk in to be the first to start this long but exciting day full of new discoveries. It’s yet another start of a typical day of a forecaster for the NASA Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) field campaign.
About 50 of us have gathered here (and 20 more to arrive later) in the middle of the continental United States in search of strong convective storms that penetrate high into the atmosphere. These so-called overshooting storms carry water and pollutants from the boundary layer and troposphere (where we live) into the atmospheric layer above us called the stratosphere. Small turrets at the top of these strong storms overshoot into the stratosphere, and hence its name “overshoots”.
The stratosphere is a much different environment than the troposphere. For one, it is extremely dry. It also has many molecules of ozone that make up the ozone layer which protects us from harmful ultraviolet rays. Various materials pumped up from the troposphere into the stratosphere by these overshooting storms may alter the chemistry and composition of the stratosphere, which could ultimately affect Earth’s climate quite significantly. So we’re here to find out exactly how and to what extent these strong convective storms influence our climate.
Our vehicle for exploration is NASA’s ER-2 high-altitude research aircraft. The ER-2 is a single-occupant, lightweight airplane with a long (31.5 meter) wingspan that flies gracefully at altitudes up to 70,000 feet in the stratosphere, which is about twice the altitude of commercial airplanes. Air is so thin at those high altitudes that the pilot must wear a pressurized spacesuit in case of a loss of cabin pressure. Inside the nose, body and pods under each wing is like a jigsaw puzzle of many scientific instruments. Each instrument measures specifics gases in the atmosphere which are later analyzed to hopefully tell us a story about how convective storms affect the stratosphere.
My role in DCOTSS is to lead a group of forecasters and flight planners to provide our best assessment of where the outflow plumes from overshooting storms may be located on the day of a science flight and then design a flight plan to sample those plumes. This is no easy feat as these plumes of overshooting material are often tenuous and sparse such that our effort often feels like a search for a diamond in a haystack.
As we rub our just-awoken eyes and scrutinize the early morning images of overshooting plume forecasts from satellite and radar-based models, the instrument scientists begin to arrive at the hangar to prepare their instruments for a 6 to 7 hour flight. The flight plan is tweaked, the pilot is briefed, and we are ready to go.
Watching the pilot navigate the ER-2 just as we had planned is very humbling and satisfying. But at the same time, our nerves are running high as the measurements from the instruments start to trickle in from the aircraft to the mission operation center on the ground. How good was our plume forecast? Do we see any indication in the measurements that the ER-2 had actually flown through a convective plume? On many occasions, it’s too early to tell. The diamond usually only shines through after the flight has been completed and after a thorough analysis of the collective measurements. Yet we are glued to our computer screens, holding our breath as we look for any signs of a convective plume in the real-time measurements.
Our job is mostly done for today, but there is no reprieve. We now look into the future to plan our next science flight. Time to hunt for another overshooting storm!
By Shawnee Traylor, PhD student in the joint Massachusetts Institute of Technology and Woods Hole Oceanographic Institution program in Chemical Oceanography / NORTHERN ATLANTIC OCEAN /
Satellites have undoubtedly opened up new ways for scientists to study the ocean, giving us global coverage of the surface of the ocean without ever having to step foot on a ship. But how can we learn what lies beneath the surface?
The classic way oceanographers study the ocean is, of course, going there. But putting together a cruise is no easy feat. They take years of planning, preparation, and enormous teams of scientists, mariners, and logistics personnel to bring to fruition. Once aboard, teams must adapt to perform delicate tasks under the demanding conditions of working at sea. Some cruises (such as this one!) run into storm after storm, which limits the ability to conduct our ship-based scientific missions.
The difficulty of science at sea has been one driving factor in the development of autonomous platforms for use in scientific research. The wide range of platforms allow us to study places and timescales that are inaccessible to ships–such as the physics of water under ice sheets, or the interannual variability of biogeochemical cycles now and into the future.
The EXPORTS campaign utilizes a range of autonomous assets to collect data over time and space, and at different depths. Gliders silently soar through the water to waypoints provided by pilots on land, collecting measurements down to 3,281 feet (1000 meters) several times a day. Autonomous floats such as the Biogeochemical Argo float shown in the photo below remain in the ocean for up to five years, gathering critical data as they drift in the ocean’s currents. Drifters deployed at the surface give insight to the upper ocean currents. Like satellite imagery, these assets allow us to make informed decisions while at sea by scouting out the biology, chemistry, and physics of a region without having to move the ship. The assets that remain in the water after the cruise continue our study and give further context to our ship-based measurements.
Each type of platform carries a unique sensor package, though most of them measure temperature, salinity, and depth. The floats and gliders utilized in the EXPORTS cruise also include a suite of biogeochemical sensors that measure oxygen, bio-optics, and nitrate. The bio-optical package measures things like chlorophyll, a proxy for the abundance of phytoplankton, and backscatter, which is used to study particles in the water that may be important to carbon export.
On this cruise, I was tasked with deploying two BiogeochemicalArgo floats, to both inform our mission while at sea and enable us to continue our study of the region after we return home. Similar to gliders, these floats move through the water column by finely tuning their buoyancy by moving mineral oil between internal and external bladders. When it is time to take measurements, they sink down to 6,561 feet (2,000 meters) and begin gathering data on their way to the surface, constructing a profile of the water’s properties. Once at the surface, they transmit this data back to servers on land via satellite, who process and send it back to the team on the ship.
We deployed the floats in the first few days of the cruise, transiting over the first drop point at 4:30 AM. The brisk early morning air stole any lasting grogginess from my eyes as I grabbed a drill and opened their wooden crates. I hooked two alligator clips onto the head of the float and successfully made communication, waking it from its slumber. After a few final pre-deployment checks, it was the moment of truth. My fingers hovered above the keyboard, ripe with the responsibility of ensuring a successful deployment. One final keystroke activated the float, and it was time to release it into the vast black waves. How I wished for a blinking light, the purr of a motor, or any sign of life. But it stood silent. I had to trust that once we released it overboard, it would rise once again.
By Laetitia Drago, PhD student at Sorbonne Université / NORTHERN ATLANTIC OCEAN /
As a child, I used to spend my summers on the rocks near the water in Villefranche-sur-mer, France, my hands busy with a bucket and a small net. I was fascinated by the organisms surrounding me both on the rocks and in the water. Little did I know that I would have the chance to explore the open ocean with a bigger hand net, and multiple imaging instruments on a 231 foot (70.5 meter) long vessel.
I started my PhD in October at IMEV in Villefranche-sur-mer, France, on the impact of zooplankton on the biological carbon pump through an in-situ imaging approach. It’s in this context that I had the privilege to join this impressive EXPORTS campaign onboard the Sarmiento de Gamboa research vessel. This vessel’s scientific team consisted mostly of people coming from the Woods Hole Oceanographic Institute, researching the ocean twilight zone, the layer of water between 656 and 3,280 feet (200 and 1,000 meters) below the surface of the global ocean. It is a very important layer of the ocean for the biological carbon pump, the process which is at the core of my PhD.
The biological carbon pump moves carbon from the surface to the intermediate and deep oceans. This process starts at the surface of the water where small plantlike organisms called phytoplankton do photosynthesis, the process of using light to transform carbon dioxide into organic matter. This phytoplankton is then eaten by zooplankton, which transfer the carbon from the surface to the intermediate and deep oceans through multiple processes such as producing fecal pellets and daily migration up and down throughout the ocean. These organisms constitute an important source of food for fish, making them an important link in the food webs supporting fisheries all around the world.
To look more closely at the ocean twilight zone, I brought imaging instruments to observe which organisms live in this layer. These included Underwater Vision Profilers (UVP). These instruments were developed in my lab in order to study large particles and zooplankton up to nearly 20,000 feet (6000 meters) in depth! The instrument counts and measures particles greater than 0.1 millimeters and saves images of the ones greater than 0.6 millimeters because those are the ones with a clear enough resolution to determine which taxonomic group we’re looking at. To do that, it uses a camera and a dedicated red light flashing system. On the image of the UVP6 you can see that there is a light. It can flash every few seconds depending on how you program the instrument. For the UVP6 for example, it was programmed to flash once every two seconds. This way, it illuminated a volume of water every two seconds below the camera, which can then take a picture of the illuminated field of view.
The UVP5 has already performed more than 10,000 profiles in the ocean throughout the 10 years since its creation. It has been used in all the oceans fixed on CTD rosettes like the one used during this cruise. CTD rosettes are submerged in the ocean to measure temperature, depth and salinity in the ocean.
I also used two UVP6s, a more versatile, small and powerful version of the instrument. Each one was in a cage, fixed to a drifting line which was deployed at sea. We hope that the images taken by these two instruments will help improve our knowledge of the biological carbon pump.
I also brought with me a Planktoscope. This microscope platform was designed at Stanford University by Plankton Planet and the Prakash Lab in the context of frugal science, which aims to bring science to the maximum number of people. It can be customized, redesigned and mounted aboard a ship by anyone in the world at a very affordable price!
Using a net or the water from the Niskin bottles (as seen in the second picture), I imaged the organisms living in the water and watched as the composition of organisms changed between the different parts of the ocean that we sampled.
Here a few images acquired by these instruments:
As you might know, this journey was not an easy one. Three storms came our way during our mission at the PAP site. Nevertheless, we managed to do 11 profiles with the UVP5 and get six and a half days of images from each UVP6 with one image every two seconds. This amounts to around 148,500 vignettes for the UVP5, 323,000 vignettes for the UVP6 and 79,200 vignettes for the Planktoscope.
The storms were unfortunate for our life on board and the conditions which stopped us from sampling during half of our presence at the PAP site. However, it was fortunate in the sense that we have a unique dataset containing data before the first storm as well as data between the three storms. This will hopefully give us an idea on the potential impacts that one or multiple storms can have on zooplankton and particle flux.
Our hard work was of course rewarded by the data acquired but also by a wonderful sunrise at the end of a very long last night of sampling followed by a 15 minute visit from a group of common dolphins on our way back to Vigo.
Finally, I want to deeply thank the team in Villefranche-sur-mer, France, who trusted me with handling the instruments and supported me from afar as well as the very motivated team of scientists and the ship’s crew support who helped us acquire very important data which will hopefully help us to understand a little bit more the carbon processes at hand in the ocean twilight zone.
By Mikayla Cote, Master’s student at the University of Rhode Island / UNITED KINGDOM /
After flying to the United Kingdom, the EXPORTS scientists were in quarantine for two weeks prior to embarking on a month-long research cruise. While there was still some last-minute work to be done before departure, for most of us this meant there would be no shortage of free time spent alone in our hotel rooms. As one of the lab mates cheering on the sailors from home, I wanted to be a part of the effort to facilitate remote activities as they anticipated their month at sea.
Cynthia Beth Rubin, an artist who has been working with our plankton ecology lab for over a decade, began offering her plankton drawing workshops over Zoom earlier on in the pandemic.
The plankton we study in our lab are microscopic plant-like and animal-like organisms, so Cynthia’s workshop aims to enable us to see and even feel these organisms’ movement through drawing since most do not know what microscopic plankton look like. While EXPORTS researchers have an idea of what these creatures look like thanks to microscopes, many in the general public don’t. Through Cynthia’s class, people are getting to see what plankton look like for the first time.
Many of those in isolation did not have access to paper typically used for drawing in their rooms, but it did not matter: lined paper, sticky notes, and even napkins were just fine. One of the postdocs in our lab decorated the hotel room T.V. with her sticky note drawings to enjoy for the rest of her time there. My favorite part of the workshop was holding up our finished drawings in front of our cameras to share with the group.
We spent a few hours together and while I cannot say exactly how those felt in isolation far away from home, this workshop offered a release to loosely draw and share sketches with others as well as a brief distraction from the global pandemic.
By Diana Fontaine, Ph.D. Candidate at the University of Rhode Island Graduate School of Oceanography / NORTHERN ATLANTIC OCEAN /
We have about one more week of full science fun left in the North Atlantic NASA EXPORTS campaign. It has certainly been a wild ride at sea given that we’ve experienced about four storms to date. However, even with the weather days, we have still accomplished an impressive amount of science.
My name is Diana Fontaine and I have been working with team grazer, alongside Heather McNair (post-doctoral researcher), Laura Holland (post-doctoral researcher) and Erin Jones (Ph.D. student). Our role in the project is to quantify microzooplankton grazing on phytoplankton. Microzooplankton are single-celled organisms that play an important role in the transfer of energy in the ocean. They are a key link between phytoplankton, the free-floating plants and algae of the sea, and larger zooplankton. Many species of zooplankton eat phytoplankton, which transfers energy to higher trophic levels. Every day, microzooplankton eat about 70 percent of the daily phytoplankton growth in the ocean. This is quite a huge loss factor of phytoplankton! Thus, understanding microzooplankton grazing rates has large ecological importance for carbon cycling in the ocean.
Measuring microzooplankton grazing involves many, many hours of pouring water and filtering. Sometimes I feel like all we do is pour water from one place to another. But so it goes as a plankton ecologist! The basis of these rates comes from measuring chlorophyll, a green pigment in phytoplankton cells that is used in photosynthesis, at the beginning and end of incubation experiments. But first we must collect the water used in our experiments from the CTD Rosette, a device that we use to measure seawater properties like conductivity, temperature and depth as well as collect seawater samples. After collection, we incubate the water in tanks on the back deck of the ship. These tanks are covered in various layers of mesh screens to imitate the light levels at different depths in the ocean. The microzooplankton hang out in the tanks for about 24 hours to give the microzooplankton a chance to have a feast on the growing phytoplankton.
Once time is up for the experiment, we again filter more water – this time to observe how much chlorophyll increased or decreased during the incubation. There are some details to these experiments that I won’t describe here. However, overall if chlorophyll increased during the incubation, then there was more phytoplankton growth than the microzooplankton were able to graze. And vice versa – if there is less chlorophyll at the end of the incubation, then that mighty microzooplankton had quite the snack! On some days we have observed happy snack time for the microzooplankton,while on others there didn’t seem to be much grazing happening at certain depths in the water column. We’re looking forward to examining these rates in greater detail once back on land.
For the remainder of the cruise, we plan to carry out a couple more grazing experiments. Both the length of this cruise and the periodic storms have allowed us to collect data under varying environmental conditions. This will make for an exciting data analysis adventure, especially when we place our results in the framework of the broader NASA EXPORTS project.
Once this next week of science is complete, we will pack up all of our gear and samples for shipment back to the United States. While it will be sad to leave our floating home for the past month or so, I look forward to the data analysis, collaboration, and writing up our results back on land. Throughout this whole experience, we have been incredibly lucky to have the helpful support of the NASA Project Office as we navigated the traveling, quarantining, and sailing during the pandemic. It has certainly been a rewarding experience to join along for the ride.
By Delfina Navarro-Estrada and Shannon Burns, oceanography graduate students at the University of South Florida / NORTH ATLANTIC OCEAN /
In the sunlit portion of the ocean exist single-celled microscopic organisms called phytoplankton. They are called the ‘grass of the sea’ because these tiny plants and algae perform many of the same ecological functions as plants on land. As such, they provide energy to the organisms higher up in the food chain that feed on them, forming the foundation of many marine food webs. Through a process called photosynthesis, phytoplankton also remove carbon dioxide from the atmosphere and use it to produce sugars and other organic compounds that they require to live and grow.
Because photosynthesis requires sunlight, phytoplankton thrive in the surface layer of the ocean. Eventually some of the carbon in phytoplankton is exported out of the sunlit surface layer to deeper waters where it can become sequestered from the atmosphere for decades to centuries. Export occurs through different mechanisms, including when organisms that get their carbon from eating phytoplankton die and sink, or produce fecal pellets that sink. Most of the sinking carbon ends up being dissolved back into the water column before ever reaching the deep sea or the seafloor. The small fraction of organic carbon that does reach the seafloor, however, ends up being buried and stored for hundreds of thousands of years. This process of carbon export is known as the biological carbon pump.
Net primary productionis a term used to describe how much carbon the phytoplankton community incorporates into their cells via photosynthesis, minus the amount of carbon released through respiration. It can be limited by the supply of nutrients and sunlight in the water column, both of which vary over space and time across the ocean. Those needed in large amounts like phosphate, nitrate, and silicic acid, are called macronutrients . Other nutrients are needed in comparatively smaller amounts and are called micronutrients, which include many trace metals like manganese, iron, cobalt, nickel, copper, zinc, and cadmium.
Phytoplankton are so good at gathering required nutrients from seawater that they can run out. When that happens, their growth is slowed or stops and their composition changes in ways that affect export. They can become sticky, aggregate and sink quickly, or become poor food sources for their predators, reducing grazing and the amount of export by zooplankton that eat phytoplankton and produce fecal pellets. In these ways and others, the nutritional status of the phytoplankton can change how efficiently the biological pump moves carbon from the surface ocean to the deep sea.
As part of the EXPORTS program, we are identifying how macronutrient and micronutrient availability affects phytoplankton community composition and their physiological state to understand how these factors drive phytoplankton carbon through the biological pump.
In 2018, our team sailed in the North Pacific, a region with highly stratified waters with minimal nutrient input. Now in 2021, our team is sailing in the North Atlantic, a seasonally stratified region where eddies move nutrients from the ocean depths to the surface through a process called upwelling. We are using a combination of ultra-clean trace metal chemistry combined with the tools of molecular biology to understand how phytoplankton are responding to the changes in nutrients in their environments.
Our team is trying to understand how different organisms respond to the changing nutrients? Working with the rest of the EXPORTS science team, we will combine measurements of carbon export, and ultimately the amount of carbon dioxide sequestered from the atmosphere.
By Ken Buesseler, Woods Hole Oceanographic Institution /NORTHERN ATLANTIC OCEAN/
For those of us who grew up watching Gilligan’s Island, we all know the fateful story of the “three-hour tour.” Well, as this oceanographer knows, that TV storm is not that different from the weather we are facing out here in the North Atlantic on the research vessel Sarmiento de Gamboa.
Our story takes significantly longer than three hours, as we set off at the beginning of this month on a three-week tour – 18 days to be more exact. Add in three years of planning the science mission, plus two years of coordinating three research vessels to rendezvous at the same time and location, one year of COVID-related delays, two weeks of quarantine in a hotel in Vigo, Spain, and you get the idea of how much time and effort we expended before we even left the dock.
Our mission is to gain a better understanding of the mysteries of the ocean’s twilight zone. The twilight zone refers to the vast layer of the ocean below where sun penetrates and above the abyssal dark ocean. At the surface, marine plants, or phytoplankton, convert carbon dioxide into organic matter just like plants on land. This organic carbon is the food supply eaten by zooplankton, or microscopic animals, and then fish and other animals up the food chain. As they eat, they expel fecal matter – yes, poop – which attaches to other particles in the water, and forms what scientists call “marine snow.” Typically, only a small fraction of the marine snow makes its way downwards through the twilight zone to the deep sea.
The reason we need to pay close attention to marine snow is that it plays an important role in climate regulation. Marine snow carries carbon with it and settles into the deep ocean, which influences the levels of carbon dioxide in the atmosphere and thus affects our climate and weather on land.
So we are out here to capture the marine snow fall, to better understand its variation, and predict how it will change in the future.
Mother Nature has her own agenda.
Two days after sailing northwest from Vigo, Spain, we reached our study site where two vessels, the RSS Discovery and the RSS James Cook, have already started sampling.
So far so good.
After 36 hours, winds pick up to 50 knots and seas quickly swell to 15-20 feet or more. The Captain makes the call to stop all science operations. At that point, we double-check all the ropes, ratchet straps, and bungies holding down our expensive scientific gear in the lab, feel gratitude for having strong, seafaring stomachs (or at least I do) and wait.
With the hatches locked, we hear and feel waves crashing into the ship. We wonder if the rolls can get even larger than 30 degrees. We head 100 miles south to avoid the worst of the storm. And we wait.
We chat with each other, read books, and watch videos. We go to normal meals in the mess, amazed that the cooks on board can still prepare a full, hot meal in these conditions. We use one hand to steady our plates, the other hand to hang onto the table. Occasionally we manage to shove some food in our mouths.
After four days, the weather improves enough to allow us to sample again.
We enjoy 36 hours of continuous science operations. At one point, we bring all three large vessels together (a few ship lengths apart) to compare results from common instruments used on each ship.
Our ship carries new technologies to add “eyes in the twilight zone” using different on-board and robotic imaging systems that we deploy for autonomous missions.
A second ship carries out survey work, following and crossing circular tracks that the ocean currents make out here called eddies.
The third ship stays faithfully in the center, following the same patch of water, focused largely on marine biological processes and their chemical and physical controls. They deploy unique devices to capture the marine snow fall directly.
Quite simply, we need to work together to put all the puzzle pieces together. But Mother Nature has more in store for us.
We get hit a second time with 48 hours of waves and winds. This time we head north to avoid the worst of it.
And again, I find myself sitting and waiting, not stranded on an idyllic island like Gilligan and the party of the Minnow (the professor character always appealed to me the most) but stuck on a 230-foot research vessel, waiting to get back to the work we came here to do.
Despite the rough seas, I love my job. The understanding we gain by visiting these remote and sometimes stormy places, makes up for the discomfort and effort it takes to be here.
As we weather the final dregs of the storm, I can’t get the theme song from Gilligan’s Island out of my head “just sit right back, and you’ll hear a tale…”
I’ll certainly have some tales to share.
We’ve already been sharing data between the ships. In less than a week, we will pack up our gear, and bring our samples and data back to the Woods Hole Oceanographic Institution. We will share our science stories, as well as stories of raging seas, and the challenges we face just to do our jobs.
All these experiences remind us of what we can and can’t control as we work to better understand this ocean planet.
By Zachary K. Erickson, NASA Goddard Space Flight Center / GREENBELT, MARYLAND /
The ocean is full of eddies – swirling water masses that are the ocean equivalent of hurricanes. In comparison with their atmospheric counterparts, eddies are smaller, longer-lived, and far more numerous: at any given moment, well over 1,000 eddies exist throughout the global ocean, with diameters typically between 30 and 200 miles (about 50 to 300 kilometers). On average they last for one or two months, but about 20% last for four months and a small fraction can last for over a year.
We decided to locate the North Atlantic EXPORTS field deployment within an eddy because eddies tend to trap water masses in their core. This means that if we put multiple instruments in the eddy core, we can be pretty sure that they will stay close together. In a campaign involving dozens of individual instrument platforms, it is much easier to organize and understand the measurements when they are all near each other! Additionally, if the eddy core primarily contains trapped water, we can interpret changes in the water properties – such as a decrease in nutrient levels or an increase in biomass – as resulting from biological processes happening within the eddy, rather than from other external factors.
The main way we look for eddies is by using data from a constellation of satellites continuously orbiting the earth. These satellites use radar to very precisely measure the height of the ocean surface. On a global scale, these measurements help scientists track sea level rise. Locally, we use these measurements to track eddies, which either look like hills or valleys in sea surface height depending on if they are rotating in a clockwise or counterclockwise direction (in the northern hemisphere; this is flipped in the southern hemisphere). A sea surface “valley” is directly analogous to the low pressure associated with hurricanes, which rotate in a counterclockwise direction (in the northern hemisphere).
Once we find an eddy, we try to predict how long it will last. For the EXPORTS field deployment, it was important to pick an eddy that was going to last for at least a month, which is the length of the main part of the deployment. We look at data from years past to identify characteristics of eddies that are long-lived, such as their size (bigger is better) and how symmetrical they are (circular eddies are better than oblong shapes). We also use numerical simulations to drop “particles” in a given eddy and track whether or not they appear to be trapped within the center or if they escape from the eddy. From these we generate a prediction for each eddy of how long, and how well, it will trap water masses within its core. For this experiment, we want a long-lived eddy that effectively traps water!
After we have a small number of candidates, we need measurements from instruments in the water. It is very important to know what the eddy looks like beneath the surface, below where we have data from satellites. The EXPORTS project is centered around measuring carbon “export”, or how carbon locked up in biomass is transported from the ocean surface to the deep ocean interior. So, it is important that our chosen eddy effectively trap water masses down to about a thousand feet (about several hundred meters).
Initially, we get these measurements from ocean gliders, autonomous platforms that adjust their density to move up and down within the upper 0.6 miles (about 1 kilometer) of the water column, taking measurements of temperature, salt concentration (salinity), oxygen levels, and biomass along the way. Three gliders were deployed in early April, and these measurements were supplemented by data from three research ships in May, as well as the aforementioned dozens of platforms deployed within and around the eddy.
Throughout the course of the field deployment, a group of scientists on “shore duty” (including numerous institutions such as NASA Goddard Space Flight Center, University of Washington, University of Rhode Island, CalTech, University of California Santa Barbara, Woods Hole Oceanographic Institution, and the National Oceanography Centre in the United Kingdom) use all of these data to track daily changes in how our chosen eddy is evolving over time, making sure that we center measurements on the core mass of trapped water in the center. There’s still a chance that the eddy will break up, but two-thirds of the way through the mission, all evidence points to our having made a good choice in picking an eddy that will stay present at least throughout the course of this field deployment, and perhaps for many weeks or months afterwards!