Something impossible to see with the naked eye: phytoplankton. Something newly possible to see from space: phytoplankton.
Earlier this month, NASA launched a new satellite, PACE (which stands for Plankton, Aerosol, Cloud, ocean Ecosystem), which will measure the presence, concentration, and types of phytoplankton in bodies of water around the world (as well as those other initialisms in the name) from the comfortable distance of Earth’s orbit.
NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite launched earlier this month. Credit NASA
Since the PACE mission only launched about 2 weeks ago, it’s not yet in information-gathering mode, but I wanted to learn more about the PACE mission and why this new data is important, so I called Jeremy Werdell, the project’s scientist at the Goddard Space Flight Center in Greenbelt, Maryland.
An algal bloom in the Baltic Sea from summer 2018, captured by a different NASA satellite. Credit Joshua Stevens and Lauren Dauphin, NASA Earth Observatory
He explained that this new mission will allow NASA to get a better sense of what on earth is happening, on both short and long time horizons. With aerosols, that’s air quality and what kind of pollutants might be present, especially in underserved communities without access to air quality monitoring but who might suffer from poor air quality in the short term. In the long term, it will enable scientists to understand the kind of warming or cooling effect certain aerosols might have on the planet as a whole.
For plankton, the specific communities (and their size) have implications for food security and the economy — recreational fishing, commercial fishing, tourism for beneficial species; beach closures, food and water contamination for harmful species in the day to day — and collecting that information and making it available to stakeholders might help with those economic and nutritional concerns, but also conservation efforts. In long-term analyses, we can see patterns of global carbon cycling, changing distributions and migration patterns that might accompany them.
It’s easy to forget the relevance of NASA’s experiments and data collection to our everyday lives, or why space missions and satellites really matter to us on earth. But it is because of NASA (and the efforts of other space agencies) that we know that the climate is changing; it is because of NASA that we know how it’s changing, how all of the changes interact with each other, how the climate will change going forward, and what all of those changes might mean for life on earth for future generations.
NASA, using other satellites, has previously been able to extrapolate the presence of phytoplankton from other measurements, such as the amount of chlorophyll and the water temperature, and forecast the amounts in which it is likely to occur. But PACE will be the first satellite that can detect what kind of algae is present — it’s equipped with a hyperspectral ocean color instrument, which can measure the ocean and other bodies of water across the spectrum from ultra-violet to infrared light. Scientists can then determine which communities of phytoplankton are actually present on a daily, global scale, which will be used to track changes in the ocean environment, better understand the carbon cycle, and forecast harmful algae blooms, letting fishers or other stakeholders know that it might not be save to harvest fish or shellfish from certain areas, since eating animals that have likely eaten toxic algae generally makes people sick.
The other things PACE can track — aerosols, clouds — are also really important. The uncertainty around the behavior of aerosols and how clouds form is one of the reasons why there are often such big error bars around estimates of how much warming different amounts of greenhouse gas emissions will cause. There are also lots of different sources of aerosols — emissions from volcanic eruptions, from ships burning fuel, from wildfires — and understanding which aerosols came from where, how they are behaving and interacting with each other, the atmosphere, and the ocean, will help scientists place firmer boundaries around our various warming scenarios.
All of these interactions can help explain many of the new and unusual patterns we’re seeing in global temperature swings, changes to the carbon cycle, and more. For example, extremely hot ocean temperatures this past summer had a combination of causes: global warming and El Niño, but also possibly declining amounts of sulfur dioxide aerosols from ship engines (new international regulations require ships to use cleaner fuels or scrub these harmful particles from their engines) and anomalously low amounts of Saharan dust, both of which normally reflect heat back to space, but smaller quantities of these reflective particles mean that more heat gets absorbed by the oceans. Being able to tell which part is responsible for the changes we are seeing can help make modeling better for the future, and instruct policymakers where to deploy resources.
Aerosols as seen from space. Credit Joshua Stevens, NASA Earth Observatory
And there are exchanges between earth and sea and sky that we also don’t fully understand, at least not on a global scale, Dr. Werdell said. “It can happen in both directions: some compounds that phytoplankton release can form cloud formation nuclei; but there’s also aerosol deposition into the ocean, which can initiate phytoplankton growth.”
After the catastrophic Australian wildfires in 2019-20, aerosols from the fires “blew to the southeast offshore to a desertlike section of ocean” Dr. Werdell said. It turned out that those aerosol deposits from the wildfires fertilized the Southern Ocean, according to a study.
Algal blooms off the coast of Australia after the wildfires in 2019-2020. Credit European Space Agency via coastalreview.org
“Without the vantage point of space you can’t think about how this happening globally,” he said. “It’s not like anything in the atmosphere obeys political boundaries — things go where they want. And that’s true for the ocean, plus it’s a 3-dimensional space. It’s not like land plants where you can see where they go — if you don’t see it today chances are you won’t see it again.”
Our discussion also reminded me of a book I’ve written about here before, Beyond Measure by James Vincent, about the history of measurement, but which I happen to have just reread. One of the themes that runs throughout the book is that the ways in which we understand the world — the questions we ask, the answers we get — are biased by the instruments we make that allow us to measure. We might think we know certain “facts” about how aerosols behave or how they interact with the ocean, but we may also be blinkered by the imprecision of the tools we have, and our understanding could change as a “better” tool — a more precise one, or one that measures with smaller increments — comes around. That’s not to say that there aren’t facts or physical realities, but that human subjectivity controls the measurements as well as the results, and we have to be aware that how we measure and who is doing the measuring also dictates what we measure and what we use those measurements to do.
In a chapter on the development of statistics, Vincent writes about how the improvements in measurement tools in astronomy — like the telescope — corresponded with more errors. As Vincent writes, it may seem paradoxical at first that more precision could lead to more mistakes, but:
“If you have to measure your height twenty times in quick succession, the first ten times using a tape measure marked in feet and inches, and the second ten using a laser that judges length to the millimeter, which set of results will show more consistency? It’s easy enough to hit the mark of 5 foot 10 inches ten times in a row, but measuring out 1.778 meters over and over again is a bigger challenge…this is one of the fundamental traps of measurement: the more precise you are, the more inconsistent your results often appear to be.”
Later on, he connects this to the doctrine of “fallibilism,” the idea that all knowledge is ultimately contingent, developed by Charles Sanders Peirce, “a mathematician, philosopher, and metrologist…the first to experimentally tie a unit of length to a constant of nature.” Peirce wrote, “We can never be absolutely sure of anything, nor can we with any probability ascertain the exact value of any measure.”
That’s not to suggest that it’s not worth it to measure, or to develop better instruments, to experiment and ask questions again and again. Rather, that science is always changing, which should be an exciting prospect — there’s always more to find out.
As Dr. Werdell said, “This ability for discovery” from all of the new measurements and the permutations of how to interpret them with new tools like machine learning and artificial intelligence “on top of the interconnectedness of sea and sky, this is why I wish I were a student again, because the sky’s the limit, and for the first time in my career, the pun is not intended.”
This was originally posted on Tatiana’s Substack News from a Changing Planet, a free twice-monthly newsletter about what on Earth is happening, with articles and essays about climate change and the environment.
Banner photo: Credit Joshua Stevens and Lauren Dauphin, NASA Earth Observatory.