As an engineering intern at Ice911, my job involves a heavy dose of creativity. I get to imagine the frigid and demanding deployment conditions of the technology I create. For Ice911 to answer our scientific questions in the Arctic, we have to design systems which reliably record and report information about ice and weather -- all in an extreme and dynamic environment.
For instance, in order to test whether spreading reflective microspheres makes ice last longer before melting, we need a way to measure ice thickness throughout an entire spring season. Though it might sound benign, spring is quite extreme in the Arctic! Temperatures 20-degrees below zero, gale-force winds, crushing pressures, and melting ice conspire to make the Arctic too dangerous for scientists to take these measurements in person.
Luckily, experts have established a huge body of knowledge to tackle the problem of collecting Arctic data remotely. There are weather stations, autonomous drones, and ingenious satellites outfitted with the instruments scientists use to get the data they need. Perhaps the most direct way to collect this information is with a floating buoy that takes measurements from the ice. At Ice911, I’ve gotten to work on our next-generation buoy, which involves researching the state of the art in Arctic buoy design.
I’m excited to share with you 8 things I learned showcasing the creativity and imagination that buoy designers have used to overcome the profound challenges of extreme science measurement.
#1—What is a buoy?
A buoy, simply put, is something that floats. It can serve many purposes. The buoy in the photo on the left, for instance, serves as a speed limit marker. (Incidentally, this buoy photo earned me two concert tickets when I submitted it to a radio contest. Talk about “serving many purposes!”)
Scientists use buoys to measure all sorts of things. At the University of Washington’s Marine Renewable Energy Lab, researchers use buoys to hold underwater listening devices to test the ecological safety of marine generators. Researchers at Dartmouth College’s Cold Regions Research and Engineering Laboratory (CCREL) did some of the early work on measuring ice thickness with buoys. In the photo on the right, you can see Ice911’s own ice monitoring buoy.
#2—What do buoys look like?
Buoys have interesting and diverse shapes and sizes. Form follows function: the speed limit buoy above is large and stable so it can remain at anchor for a long time, while Ice911’s buoy is tall and light-colored so it can measure thick ice heating up in the sun.
The International Arctic Buoy Programme, a centralized resource for arctic buoy data, provides a set of fascinating buoy photos with descriptions on its website. Some of them have probes for penetrating the ice after being dropped from an airplane, while others have sonars that dangle in the water pointing upward. Other buoys rely on the ice remaining frozen to stay out of the water, and don’t have any flotation at all! It seems generous to call those “buoys”, but that seems to be agreed upon.
#3—Who uses buoys?
Many people use buoys, far too many to name here. Fishing floats have been used for thousands of years, and mariners have used floating markers for centuries. Modern buoys are used by oceanographers to measure ocean currents; the Coast Guard to warn of hazards to navigation; the National Oceanic and Atmospheric Administration to measure weather phenomena; the Navy to keep track of stray submarines; and one final example, marine biologists to listen for whales.
#4—How do buoys measure ice thickness?
There are three popular ways for buoys to measure ice thickness. The first way involves measuring the distance from buoy-mounted sensors to the ice surface. To do this, buoys report measurements from above and beneath the ice using sonar. If you know the distance between the two sonar sensors, then you can determine how thick the ice is. That strategy is used by the CRREL program’s buoys to measure ice thickness.
A closely related strategy has been used by submarines since World War II. Many submarines have upward-looking sonars that measure their distance from the ceiling of water or ice above. They also know their depth very precisely from observations of water pressure. By subtracting the distance to the ice above from their pressure depth below sea level, they can determine how far the ice extends beneath the surface of the water: a measurement called “ice draft”. Ice draft correlates with total ice thickness, but it differs by the level of snow and ice above sea level (think “the tip of the iceberg”). Even though it is not a direct thickness measurement, submarines have generated thousands of miles worth of ice draft data, making it a large and valuable dataset.
In my opinion, the cleverest technique to measure ice thickness is with a “temperature string”. These are two-meter long cables containing regularly-spaced temperature sensors and heaters. In order to tell which sensors are in air versus water, temperature measurements are taken before and after turning the heater on for a minute. Because air, snow, ice, and water have different heat capacities, each of those materials heats up a different amount after activating the heater. When you plot the change in temperature at different heights along the string, it is possible to distinguish the layers of material surrounding the string. The image below shows how the plot of temperature change versus string height evolves over time. You can see the ice continue to grow throughout the winter!
#5—How do Arctic buoys measure sunlight?
To measure how microspheres reflect the sun’s energy, polar researchers use devices called “net radiometers”. The name is apt because they measure net solar radiation: using separate instruments facing upward and downward, these instruments record the incoming and reflected solar energy, which tells you about the net flow of energy. Net radiometers let you precisely quantify how snow reflects energy, which is crucial to understanding our material’s albedo. The image above shows the Apogee SN-500, a widely-used net radiometer.
#6—How do Arctic buoys relay their measurements to scientists?
Because buoys frequently operate far from WiFi or cell service, buoys often communicate via satellite link. Ice911’s buoy uses a connection to the Iridium satellite constellation to upload its data via a small computer. This is a common solution for Arctic buoys, though some buoys use the Argos satellite communication system or the ham radio band.
#7—Why are Arctic research buoys important?
The International Arctic Buoy Programme lists five prominent uses of arctic buoy data. In general, Arctic buoys are vital for climate change research due to the Arctic’s uniquely influential role on the global climate. They help forecast weather and ice conditions. Buoys also help validate data from satellites that remotely measure the thickness and extent of sea ice. Climatologists feed buoy data into climate models to test their predictions against real-world measurements. Additionally, buoys offer context to interpret samples of ice taken from the surrounding areas.
At Ice911, research buoys are a crucial method of gathering data to test our scientific hypotheses. We use buoys to measure ice thickness, solar radiation, temperature, wind, and many other important values that let us characterize the impact of albedo-changing material on Arctic sea ice. Buoys are an essential method to investigate albedo modification: which is important because restoration of Arctic ice is the single most effective safe lever on climate change we know of.
#8—How much do they cost?
Buoys are expensive! To collect the data we need on ice thickness, solar radiation, and other climate variables requires expensive instruments that we must buy from outside vendors. A full sensor suite for a single buoy can cost well over $10k, and after factoring in the cost of computers and the buoy itself, and the cost of our own engineering time, the price can creep far higher. But, though expensive, this is critically important, as it’s a direct investment in high-quality completion of science objectives. By adopting multiple industry-standard instruments, we can be certain of our ability to accurately monitor the safety and efficacy of increasing ice albedo.
How you can support our buoy research
Upcoming Arctic deployments of our reflective microspheres will require us to purchase at least 4 new buoys, and this is an area where you can make a profound and immediate impact. Our Arctic Buoy Program allows donors to name one. Just, please, no Buoy McBuoyface.
Written by Tim Player