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Salinity Processes in the Upper Ocean Regional Study (SPURS): Snakes on a Ship!

August 31st, 2016 by Eric Lindstrom

By Eric Lindstrom

Salinity snake

A longstanding technical challenge for oceanography has been how to measure the sea surface – temperature, salinity, gas exchange, or surfactants – to name a few examples. Obviously enough, the surface is where the ocean and atmosphere interact and exchange heat, freshwater, gases, momentum, and particles of all kinds. So, how do we measure the properties and exchanges right at the surface? If we are on a ship or any floating platform, the platform disturbs the surface. From satellites we can measure many properties of the surface but only on very broad scales. The R/V Revelle, right now, is the ship showing how modern science is meeting the challenge. Let me tell you about some key elements.

Julian Schanze from Earth and Space Research in Seattle and Jim Edson from University of Connecticut have brought two instruments aboard with innovative ways to measure the temperature and salinity at the surface – the Sea Snake for temperature (Edson) and the Surface Salinity Snake (Shanze) for, obviously, surface salinity. The former places a temperature sensor at the end of flexible hose that is hung outboard from the bow of the ship (near the wake), to continuously measure temperature. The Salinity Snake, outboard of the wake passes water through a vortex de-bubbler and thermosalinograph to obtain an estimate of salinity within inches of the ocean surface. It is an awesome “contraption” (with no offense to Julian).

The Salinity Snake being deployed over the starboard side.

The Salinity Snake being deployed over the starboard side.

Julian Schanze's birthday balloon.

Julian Schanze’s birthday balloon.

Today is Julian’s birthday so all the Salinity Snake gear has been draped with colorful paper snakes carrying birthday greetings. Julian participated in SPURS-1 in 2012 and has since received his PhD and is making a name for himself by tackling surface salinity science from gadget to satellite and from seawater intake to space. It is wonderful to have someone so capable on the NASA Ocean Salinity Science Team!

Andy Jessup, our chief scientist from University of Washington Applied Physics Laboratory and Michael Reynolds from Remote Measurements and Research Co. in Seattle have brought a dazzling array of instruments for measuring and probing the skin temperature of the ocean. The surface of the ocean is known to have a cool skin at the molecular level. Photos of the sea surface with infrared cameras reveal complex and interesting patterns as a result of mixing, wave breaking, surfactant conditions, and wind. NASA has always had a deep interest in skin temperature because satellites do measure this skin temperature while every probe you stick in the ocean measures something deeper and different than skin temperature. From the Revelle, Andy and Michael are using several infrared radiometers and cameras to measure and depict the sea surface skin temperature. There is one on a boom to measure outboard of the ship wake, one mounted on the rail to look outward from the ship and another on a balloon to take infrared photos of the skin from 300 feet above the ship (the Lighter-Than-Air InfraRed System – LTAIRS.)

The laboratory end of the Salinity Snake and Carbon Dioxide analysis.

The laboratory end of the Salinity Snake and Carbon Dioxide analysis.

LTAIRS ascends toward 300 feet.

LTAIRS ascends toward 300 feet.

Eric Chan, from University of Hawaii, is aboard measuring making a suite of carbon dioxide, pH, and Dissolved Inorganic Carbon measurements for principal investigator David Ho. They study the exchange of carbon dioxide across the air-sea interface and they’re particularly interested in how rainwater on the surface of the ocean impacts the gas exchanges.

The array of instrumentation aboard Revelle is quite astonishing and the technical innovations displayed in measuring the sea surface are truly remarkable. And I haven’t even mentioned the Surface Salinity Profiler yet in this blog post. I have been teasing you with that since the start of the voyage and I PROMISE to give it a blog entry all to itself!

Today is also the birthday of the R/V Revelle Captain, Christopher Curl. I am sure I speak on behalf of the entire SPURS-2 science party when I offer him a hearty “HAPPY BIRTHDAY!” and say how pleased we are with the entire ship and crew of R/V Revelle. I guess that sharing the ship with a group of rare ocean-skin specialists with sea snakes is not how he imagined this birthday, but he is quick with a smile and will roll with our skinny offerings!

ATom: World Survey of the Atmosphere: Traveling the Length of the Atlantic Ocean, Part 2: Greenland!

August 31st, 2016 by Steve Wofsy

I have always wanted to visit Greenland, the “ground zero” for climate change. Its ice cap rises more than 3,200 meters (2 miles!) above sea level and it holds so much ice that if it all melted, the height of sea level would rise by 7 meters (23 feet). The landscape is stark and inhospitable for most plants and animals. Greenland’s location makes it very sensitive to climate change, and it has a dynamic geological history as a result. It is undergoing rapid change now, as shown in the chart below. Greenland is “ground zero” for climate change.

The loss of ice mass by the Greenland Ice Sheet from 2002 to 2015, measured by NASA's Gravity Recovery and Climate Experiment (GRACE) and by the DC8 in NASA's Operation IceBridge. Each gigaton of ice lost adds about 1 cubic kilometer of water to the oceans. The ice sheet has lost significant mass every year since measurements began in 2002.

The loss of ice mass by the Greenland Ice Sheet from 2002 to 2015, measured by NASA’s Gravity Recovery and Climate Experiment (GRACE) and by the DC8 in NASA’s Operation IceBridge. Each gigaton of ice lost adds about 1 cubic kilometer of water to the oceans. The ice sheet has lost significant mass every year since measurements began in 2002.

For our flight to Greenland, the DC8 took off from Lajes air base in the Açores and headed directly to the ice sheet, traversing its length along the western edge. Our destination was the Canadian scientific base at Eureka (80o N), off the northern coast on Ellesmere Island’s Fosheim Peninsula. Instruments at this station record the total amount of greenhouse gases and pollutants between the Earth’s surface and the Sun. Our goal was to measure these gases at each altitude in the atmosphere, in order to check the accuracy of these data. We would then head south and land at Kangerlussuaq, on Greenland’s west coast.

The ice cap was mostly covered in clouds until we reached the northern part of Greenland. When we saw the ice surface, it showed many dark features, including melt ponds and dark hills, especially at the edge of the ice sheet.

Lonely iceberg floating at off the eastern coast of Ellesmere Island, Canada. Satellite data show that areas around Ellesmere Island, that formerly retained floating ice all year round, are now ice free like the waters in this image.

A lonely iceberg floats off the eastern coast of Ellesmere Island, Canada. Satellite data show that areas around Ellesmere Island that formerly retained floating ice all year round are now ice free, like the waters in this image.

While flying over Ellesmere Island, I snapped a photo that dramatically illustrates how dark surfaces put heat into the atmosphere. The picture shows currents of air being warmed by dark, ice-free rock, rising up along the slopes of small hills and producing the little cloud right at the top of each one. This is the way that heat absorbed by the rocky surface is distributed throughout the lowest layer of the atmosphere.

The rocky hills of Ellesmere Island absorb energy from sunlight and from heat radiated by the atmosphere ("longwave radiation"). This unusual photo shows the warm, dark rocky surface heating the air, causing warm plumes to rise and forming small cloud caps over each hill. The process efficiently transfers heat from the surface to the atmosphere (Photo: Steve Wofsy).

The rocky hills of Ellesmere Island absorb energy from sunlight and from heat radiated by the atmosphere (“longwave radiation”). This unusual photo shows the warm, dark rocky surface heating the air, causing warm plumes to rise and forming small cloud caps over each hill. The process efficiently transfers heat from the surface to the atmosphere (Photo: Steve Wofsy).

When we flew out over the sea, we could see that the waters off shore were almost completely free of ice. Occasionally we saw a few icebergs, or small amounts of ice near shore, but otherwise we saw very little floating ice.

The floating ice in the Arctic does not store a great mass of water like the Greenland’s land-based ice sheet, but it does have a very strong influence on regional climate. When the ATom mission started in early August, we flew over the Beaufort Sea north of Alaska, up to 80oN, and saw ice floes covered with dark melt ponds and interspersed with dark areas of open water. Ice started to break up in this area especially early this year, and with all that dark water absorbing heat from the sun and from the atmosphere, I wondered if most of the Beaufort Sea might become ice free by summer’s end. Now we were back!

Satellite data show that the Arctic Ocean did not lose all of its ice. But the Beaufort Sea did lose its floating ice, as far north as 75o N, and 30 to 70% was lost at 80oN. Water temperatures became quite warm off the Arctic coast of Alaska, maybe just about swimmable for a New Englander like me (5 – 10 C, 40 – 50 F). This large expanse of warm water will tend to make the fall season warmer and provide more snowfall in the Arctic than in former times, when the ice persisted more extensively on the ocean surface. The loss of floating ice amplifies itself, a process called “positive feedback.” As open water and melt ponds cover more area, the ice and surrounding water absorb more energy, leading to more ice loss, more energy absorbed, etc.

This year the overall loss of floating ice was among the greatest ever observed, although it did not quite match the record set in 2012. Indeed, as we were flying over Ellesmere, the large luxury cruise ship Crystal Serenity was reportedly starting the first crossing of the fabled Northwest Passage by a ship of its type, with 1000 paying passengers.

I also photographed the calving edge of a huge tidewater glacier, where huge pieces of ice (bigger than a football field, weighing 1 million tons or more) break off the glacier and drop into the sea. In this picture, you can see how dark the surface of the glacier has become as it travels to the sea, in contrast to the clean blue ice below. The darkening accelerates the melting of the glacier; it is due to deposition of some of the pollutants (soot) that we measure, and also to algae that grow on the ice. Scientists don’t yet know how much of this dark material is “natural” versus human-caused, and they are studying the ice to understand how much darkening is caused by deposition in the form of soot from fires or by pollution-related nutrients that stimulate the growth of algae.

he end of the line: calving front of a tidewater glacier in western Greenland. As ice flows down from the Greenland ice cap to the sea, the surface darkens due to deposition of atmospheric pollutants and growth of algae. The picture shows the boundary where the moving glacier enters the ocean. Huge pieces of ice break off ("calving") the leading edge and drop into the water—the origin of icebergs. (Photo: Steve Wofsy)

The end of the line: calving front of a tidewater glacier in western Greenland. As ice flows down from the Greenland ice cap to the sea, the surface darkens due to deposition of atmospheric pollutants and growth of algae. The picture shows the boundary where the moving glacier enters the ocean. Huge pieces of ice break off (“calving”) the leading edge and drop into the water—the origin of icebergs. (Photo: Steve Wofsy)

After flying over Eureka and the west coast of Greenland, we landed in Kangerlussuaq, just a short distance south of the Arctic Circle.  The area around Kangerlussuaq is stark and beautiful. The town is very reminiscent of many communities across the Arctic. It lies in the midst of a deglaciated area of bare rock mountains and a thin layer of tundra, in a lovely fjord. The river roars like a freight train as it goes under the bridge, carrying meltwater from the ice cap to the sea. The weather was very warm and dry. My afternoon run was interrupted by an encounter with a musk ox. The Sunday dinner at the Boat Club may have been the best of my month long trip around the world, featuring at least eight types of smoked or cured fish. This country is really breathtaking. But it was also a rather sad place, very, very quiet, with dozens of buildings left empty after the closing of the extensive military facilities when the Cold War ended, and the summer had been much warmer than average, drying up soils and plants.

After two days in Kangerlussuaq, we set out for home across Arctic Canada, arriving for a brief overnight in Minneapolis. We stayed at a hotel just across the road from the Mall of America, a vast place with reportedly 30-40 million visitors per year. The contrast with Kangerlussuaq was very dramatic—scenery, culture, sounds, smells, climate, air quality.

This transition was in many ways so typical of the ATom experience, and ATom science. We went from the high desert, with its fires and searing heat, directly to the floating ice near the North Pole, then Hawaii and American Samoa in the subtropics, then suddenly to winter in New Zealand and Chile, back to the subtropics on Ascension Island and the Açores (Portugal), and then again to a land of ice caps and glaciers in Greenland – all in the space of three weeks.

We measured the chemicals in the atmosphere, from bottom to top and along the whole route, and all in the space of just over three weeks. We saw some stunningly dirty air even in the middle of the ocean, in the subtropics and in the Arctic, with a lot of pollution coming from biomass fires, and also some very clean air. Our instruments are extremely sensitive, though, and in even the remote region of the Antarctic polar vortex, we appear to have detected traces of pollution.

After traveling on the DC8 across both the Atlantic and the Pacific, the world seemed smaller than ever before, and the atmosphere, not at all infinite or inexhaustible.

The goal of ATom is to learn about how the most remote parts of the atmosphere are affected by pollutants emitted on land. We have a lot to work with! It will take months to analyze our data and really understand what we have measured, and to assess what we have learned about humanity’s impact on air quality and climate. We also have a lot of memories and impressions (and some sleep to catch up on). I know it will take me months, or years, to fully process what I have experienced and, along with the wonderful ATom team, to extract the quantitative scientific information we need to understand the environment.

 

This image shows a deglaciated region in western Greenland, with the ice cap in the background. (Inset: Map of Greenland, showing location of our landing site at Kangerlussuaq at 67o N, 50.7 W). According to Richard Alley of Penn State University, this area around Kangerlussuaq was deglaciated at the end of the last ice age, 8-10,000 years ago, but ice returned and scraped the ridges bare during the Little Ice Age, a period between about 1300 and 1870 AD during which Europe and North America had colder winters than in the 20th century.

This image shows a deglaciated region in western Greenland, with the ice cap in the background. (Inset: Map of Greenland, showing location of our landing site at Kangerlussuaq at 67o N, 50.7 W). According to Richard Alley of Penn State University, this area around Kangerlussuaq was deglaciated at the end of the last ice age, 8-10,000 years ago, but ice returned and scraped the ridges bare during the Little Ice Age, a period between about 1300 and 1870 AD during which Europe and North America had colder winters than in the 20th century.

 

The NASA DC8 Flying Laboratory in Kangerlussuaq, Greenland. Inset: Our flight paths during ATom-1. We overnighted in 11 different time zones at 10 sites (one clock shift) in 23 days, covering 65,000 km (40,500 mi, equal to 1.6 times around the earth). We made 160 vertical soundings, and measured more than 300 chemical and aerosol parameters.

The NASA DC8 Flying Laboratory in Kangerlussuaq, Greenland. Inset: Our flight paths during ATom-1. We overnighted in 11 different time zones at 10 sites (one clock shift) in 23 days, covering 65,000 km (40,500 mi, equal to 1.6 times around the earth). We made 160 vertical soundings, and measured more than 300 chemical and aerosol parameters.

Salinity Processes in the Upper Ocean Regional Study (SPURS): Whither Life in the Sea

August 30th, 2016 by Maria-Jose Viñas

By Eric Lindstrom

Sam Levang from WHOI catches a flying fish in flight.

Sam Levang from WHOI catches a flying fish in flight.

I figured I would go off topic today and discuss a disturbing observation by someone who has spent more than half a lifetime going to sea. This is my personal opinion and does not reflect any policy or perspective of NASA. However, those of you on land really need to know that humans have had an enormous impact on the large life forms in the ocean. Sure, you probably know about how we took whales to the brink of extinction, but what about the fish on your dinner table. Do you really know how much is left in the sea?

A sea turtle near Honolulu.

A sea turtle near Honolulu.

First, to minimize stating a bunch of boring facts and figures, I give you some brief but informative links below to research for yourself. This blog post is more of an emotional statement of alarm from my personal experience than that of a fisheries biologist or an expert on marine biota of any kind.

I became an observer of marine life from a very young age. I was raised in Seal Beach, California in the 1950’s when sea lions still roamed the beach. They have long departed. Most of my oceanographic life was spent in the tropical Pacific Ocean from late 1970s to present. My experience tells me has been an enormous change in the frequency of sightings of marine organisms from shipboard during those years. In the 1970s and 1980s it was a daily occurrence to see sharks, tuna, squid, and birds. Now, in the 21st century, we are lucky to see ANY of the former and few birds. Flying fish are still around but disturbingly little else swims by the ship during shipboard work in recent years. To put this in land-loving terms it feels like a rainforest filled with life is replaced by a desert of bleak lifeless sand. Sadly, this trend has been clear to me for decades and is substantiated in many ways by scientific studies. I particularly note that my personal observations coincide in time with the dramatic increase in tropical fisheries from the 1980s. Rapid depletion of large and visible marine organisms at the top of the food chain has been well-documented. A good book on this subject is “An Unnatural History of the Sea” By Callum Roberts.

Monkey geared up for fishing.

Monkey geared up for fishing.

Monkey actually caught a fish!

Monkey actually caught a fish!

Another aspect of the alarming trends in the ocean over recent decades is the growing abundance of marine debris, particularly plastics in the far reaches of the open ocean. I will devote a future blog to this subject (as I did during SPURS-1)

I do not wish to leave you with only a picture of doom and gloom. We should all pitch in to alleviate pressure on ocean ecosystems. The National Oceanic and Atmospheric Administration has created Fish Watch to help guide concerned consumers to sustainable seafood choices. I urge all who follow my blog to become concerned consumers! Also, any lessons from your past about the limitless abundance of the ocean should certainly be buried and replaced by thoughts about care and stewardship of precious and limited marine resources.

Masked booby.

Masked booby.

References:

Wild Marine Catch.

Overfishing (Wikipedia).

Marine Fisheries — The State of the Affairs.

ATom: World Survey of the Atmosphere: A Globe Trotter’s Lessons Learned

August 30th, 2016 by Róisín Commane

As we prepare for our last flight in ATom-1, I’ve been reflecting on what I should do differently next time around as we begin preparation for ATom-2, which will start uploading in December 2016 for flights starting in January 2017.

  • Packing less “stuff”

I’m a bit of a girly girl who likes her comforts. But after hauling bags for miles as we get on and off the aircraft, I’m seriously considering becoming a minimalist! The weight of the instrument laptop seems to have increased as the project has gone on, so what I consider “essential” for each stop has been streamlined to a very short list! Washing clothes has also proved easier than I thought so I could have managed with less clothes (I can’t believe I’m admitting that!) but I did wear everything I brought at some stage so nothing was a waste of space. In fact, the list of things I wish I had brought is quite short: my hiking boots! I had assumed that taking off from and landing into warm areas meant I could wear light clothes – which was true (to a point). While on each flight, I ended up wearing my thermal vest, long johns, jeans, and my ski jacket as the aircraft is so cold. My toes were particularly cold by the end of each flight! With the ATom-2 happening in Northern Hemisphere winter, we are still trying to figure out if we can borrow suitable clothes to wear when we arrive in Alaska and Greenland. But, as I’m barely 5 feet tall, with child size feet, I’ll probably end up needing to bring my own gear anyway, so maybe my snow boots can work as my aircraft slippers next time?

Róisín Commane hauling her bags off the DC8 for the final time on Atom-1.

Róisín Commane hauling her bags off the DC8 for the final time on Atom-1.

  • Better aircraft lunches

It’s really easy for me to put on weight during projects like ATom. So I’ve been trying to eat small portions of healthy food, as well as be active on days we don’t fly. My running is slower than some people’s walking but at least it’s something! For lunch on the aircraft, I have mostly eaten ham and cheese sandwiches, with some peanut butter sandwiches when we couldn’t get meat and cheese. My lunches have been functional but uninspiring. And then Shuka Schwartz wanders by with the most amazing smelling food and I get food envy! I’m still trying to figure out how he makes such good lunches. I’m open to suggestions on this as I’m not a particularly inventive chef. Maybe we can bring a few more ingredients to help construct more imaginative lunches. Or maybe I’ll just start ordering extra at dinner the night before a flight for lack of better options.

Not the most inspiring lunch… Photo by Róisín Commane

Not the most inspiring lunch… Photo by Róisín Commane

  • Planning to be out of contact

We knew internet access would be difficult in some locations but it turned out to work quite well in most locations in the Pacific. I think this gave me a false sense of confidence in internet infrastructure and I didn’t arrange to not contact people while in the Atlantic. The internet was down while we were on Ascension Island, but I did manage to send a text, from the one working phone, telling my family I arrived safely. Internet access was really expensive in Kangerlussuaq, but I have to admit that I was happy to have a break from answering emails for a few days – and I don’t think I was the only one! I think I will just plan on a complete contact black out for those locations next time so my family is not concerned.

Róisín in Ascension Island.

Róisín in Ascension Island.

  • Take more videos

This is the first time I’ve been involved in where I’m one of the ‘media people’. Like most people, I’m used to taking photos (to show my family and friends) but videos have proved to be more useful to the NASA media reps. They are doing are doing a wonderful job given how little I’m giving them to work with! We’ve also done some discussion of the science on video. It took a lot of encouragement, but I have started to not worry too much about how awful I think I look on camera or how weird my voice sounds. Instead, I’m just not looking at it 😉

Róisín Commane at Russel Glacier, Greenland.

Róisín Commane at Russel Glacier, Greenland.

As part of doing the media outreach I’ve been asking the ATom scientists and crew to think of their favorite ATom memory. Most people have great memories of places and events. I will always remember the strikingly blue melt ponds on the Greenland ice sheet and how little sea ice there was north of Alaska. But I think my favorite memory from ATom will be the people. We’ve travelled around the world on an aircraft with 42 people on board: some people left us in Christchurch while more arrived to join the adventure. In such close quarters, I was aware that little things could have mushroomed into major conflicts. But people worked really well together. Friendships were formed and the science benefited greatly from a fantastic team effort. In particular, we owe a huge thank you to the crew of the DC-8 who brought us safely around the world and made all the measurements possible.

ATom Scientists and crew are happy to be home! Photo by Michael Prather.

ATom Scientists and crew are happy to be home! Photo by Michael Prather.

 

 

 

Salinity Processes in the Upper Ocean Regional Study (SPURS): Monkey Business over the Tropical Thermocline

August 29th, 2016 by Maria-Jose Viñas

By Eric Lindstrom

The CTD team (Spencer, Leah, Janet, and Kristin).

The CTD team (Spencer, Leah, Janet, and Kristin).

The focus of SPURS-2 is the upper ocean and the fate of rainwater. However, in order to study the top of the ocean one needs to know what is going on deeper down. The beauty of SPURS-2 is not skin-deep! SPURS-2, like many prior physical oceanography experiments, requires a basic background and context of the ocean circulation environment upon which many of our other more specialized or detailed measurements can be interpreted. The two major pieces of the contextual information for us are the surface circulation and the surface salinity pattern.

The surface salinity pattern is provided by remote sensing for the largest scale and by the array of drifters and profiling floats that have been deployed with salinity sensors. Also, the R/V Revelle is collecting a treasure trove of upper ocean salinity measurements wherever she goes – with continuous underway measurements of salinity from intakes at the surface, 2 meters (6.5 feet), 3 meters (9.8 feet), and 5 meters (16.4 feet) depths. I’ll go into that in more detail in a later blog on the Surface Salinity Profiler.

The surface circulation of the ocean is largely the result of the wind and the shape of the massive deep layers below the surface. In fact it can be crudely estimated if one knows the precise shape of the thermocline – the boundary between the warm upper ocean and the vast deep cold ocean. Here in the tropics the thermocline is pretty well represented by the 20°C (68° F) isotherm. Think of the warm upper ocean as all the water warmer than 20°C and the layer below as all the water colder than 20°C. Tropical oceanographers can use the depth of the 20°C isotherm much like meteorologists use surface atmospheric pressure maps to chart the highs and lows of weather and their associated winds. Here, if the 20°C isotherm rises toward the surface locally it is associated with a counterclockwise ocean surface current. The signature of the westward North Equatorial Current is a gentle slope of the isotherm from deeper in the north to shallower in the south. This is where our Conductivity-Temperature-Depth (CTD) instrument comes into the SPURS-2 plan. We can use it to track the shape of the thermocline. I wrote about the CTD during the SPURS-1 campaign. It is still the workhorse of physical oceanography – or maybe the monkey on the back of every physical oceanographer! Our show seldom goes on without it.

Preparing the CTD to go over the side.

Preparing the CTD to go over the side.

Janet Sprintall from Scripps Institution of Oceanography and her team (Spencer Kawamoto, Leah Trafford, and Kristin Fitzmorris) are now mapping the temperature and salinity structure of the ocean well into the deep cold abyss (to 1.5 kilometers –0.93 miles– below the surface). The ocean depth is about 4.5 kilometers (2.8 miles) and the lower 3 kilometers (1.86 miles) are (for our purposes) relatively uniform and cold. Janet has planned a grid of 49 stations 30 miles apart around the SPURS-2 central mooring. These will be completed over about a week’s time. Simultaneously there will be regular sampling with the Surface Salinity Profiler between some of the CTD stations and we will optimize our meteorological measurements by limiting our speed to 10 knots (11.5 mph). So, while studies of the meteorology and near surface salinity are ongoing, as we move about the ocean, Revelle stops for an hour every 30 miles to collect necessary information on the background oceanographic conditions.

The CTD instrumentation remains largely unchanged (although perfected) in recent decades. Temperature, salinity, and oxygen sensors are mounted on the bottom of a large frame. Water sample bottles are mounted around the outside of the frame. Other instruments, such at the acoustic Doppler current profiler, may also be mounted on the frame. All data is transmitted up the conducting wire cable that is used to raise and lower the instrument. This bulky package is now easier to deploy and recover than in yesteryear due to innovations on today’s vessels. Now the Revelle has a specialized mechanical arm to get the CTD over the side and back on deck safely without much human intervention.

Monkey climbing over the water sample bottles on the CTD.

Monkey climbing over the water sample bottles on the CTD.

For my entire career oceanography has been spelled “CTD.” Knowing the temperature and salinity structure from surface to ocean depths is the key to our understanding of the ocean’s role in climate. The first global mapping of these characteristics (with CTDs) was not realized until the World Ocean Circulation Experiment in the 1990’s. Now oceanographers are working hard to understand all the physical, chemical, and biological changes associated with global warming, rising carbon dioxide levels, and industrial fishing. In that big picture, SPURS-2 might look like a small bit of monkey business over the tropical thermocline. However, we know that the resulting scientific understanding will long outlive the memory of our tiny field program in this vast Pacific Ocean!

Notes from the Field