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Nathan Kurtz: For me, I've only done airborne field work, which is very different than being on a ship.
And we're just very isolated, like the ship is really your whole world and all those people on the ship are your whole world.
And then just outside the ship is just a very hostile landscape. It's cold. There's polar bears.
There's water that can open up underneath your feet.
*Ship horn*
And so, it was a very interesting experience to
to be on the ship which was very safe and warm, and felt good.
But then we'd go out and do our fieldwork, and we'd set things up.
And we'd be out on the ice, we could feel like this is a very wild environment.
As we were transiting through the ice, we were searching for a suitable icefloe.
Something that would be thick enough that could support us
working on safely, and also survive through the year.
While searching for that floe, we had different satellite tools that we're using.
That would identify the shape of the floes. We could see how big the floes were.
But what we didn't know was how thick they were.
We went to some of these floes and we found, no. These were really thin.
We can't actually use this floe.
We looked at some ICESat-2 tracks in hopes that some of the floes that we had identified
we could see how thick they were.
It didn't work out this time, but for a future expedition
I think we've identified ways that we could utilize ICESat-2, or something like ICESat-2.
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Text: GLOBE Observer Presents
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Text: Why Observe?: Tree Height
Narrator: While there wasn't enough ICESat-2 data for MOSAiC, or the Multidisciplinary drifting Observatory for the Study of the Arctic Climate to use.
Dr. Nathan Kurtz and the team were able to locate an area with the right amount of sea ice thickness
by using different methods.
Likewise, scientists often use various methods to measure other aspectst of our planet.
Like forests.
So, why take measurements of the same thing, using different methods?
And how does measuring sea ice thickness relate to tree height?
Let's take closer look at the Ice, Cloud, and land Elevation Satellite, or ICESat-2.
Its main purpose is to measure ice thickness using its sole instrument, ATLAS.
But, it also measures tree heights as it orbits Earth.
This is doen with photon-counting lasers and algorithms developed to differentiate what environments they are measuring.
An algorithm is a step by step procedure for solving a problem
usually a mathematical one, in a limited number of steps.
Claudia Carabajal was the Deputy Lead for the Flight Science Receiver Algorithms.
One of the many subsystems of the ATLAS instrument.
Claudia Carabajal: The algorithms that process the data on the ground for ICESat-2 are tailored
directly to address that characteristics of the surface.
So they're tailored to sea ice and vegetation.
The coherence of those photons when reaching the surfaces changes.
So the algorithms need to be specifically tailored to the surface type.
Of course the comparisons against all the data sets help you.
And sometimes you need the help of an additional data set. As you're processing.
Nathan Kurtz: When I was on MOSAiC, we took specific measurements that are useful, and will be used.
By combining mutliple measurements together, we're able to
quantify and see whether ICESat-2 is making its measurements accurately and how it's needed to be done.
Claudia Carabajal: One of the ways that you can actually figure out if ICESat-2 is actually measuring
the right thing is to compare it with observations that are being collected by other means.
For example, airborne campagins, other satellite data,
and see what the surface looks like.
You can look at how things are changing in different seasons.
Narrator: Whether it's sea ice thickness or tree height, comparing data collected by different missions
and field campagins allows scientists to better understand how the instrument works.
Dr. Laura Duncanson uses LIDAR data to create 3D maps of forests.
And Dr. Nancy Glenn is currently looking at various ways in which tree height data collected
by ICESat-2 and GLOBE Observers can be utilized.
For both, tree height data adds to our understanding of Earth's systems.
Laura Duncanson: Of course we can't go out into the woods all over the planet
and measure every dingle tree on the ground.
So, for ICESat-2 these estimates of tree height,
we don't know exactly how precise they are, or how good they are in all of the different forests around the globe.
There's a lot of variability in forests.
Narrator: Just like how taking field observations and airborne data collected of sea ice thickness
can act as supplementary data to ICESat-2.
Tree height measurements collected in the field can also be used to do the same.
This supplementary data can help scientists account for variability between different
environments when looking at measurements collected by satellites.
As mentioned, tree height measurements can be taken in different ways.
One method is to use trigonometry to estimate the height of a tree.
This is the method that students and citizen scientists use.
By measuring the distance to the tree
along with angles a and b, using a handheld clinometer. Or the one built into a smartphone.
Observers can calculate the height.
Laura Duncanson: Having people go into the woods and actually measure tree height
to compare to the satellite estimates of tree height, gives us a sense of how reliable those tree height estimates are
and maybe some ecosystems that they're particularly good at doing tree height, or particularly challenged doing tree height.
Narrator: Now we know that by taking measurements of the same thing using different methods can help scientists.
Taking tree height measurements adds a whole new data set for satellites and instruments such as ICESat-2 and GEDI to compare with.
These measurements also provide content that only an observer on the ground can provide.
Like recent changes including drought, fire, invasive species and more.
Now that leaves the question.
Why do scientists study trees?
Laura Duncanson: So, for decades now we've had really good maps of where there are forests and where there aren't forests.
But we've never before known how tall those trees in those forests are.
And this is a really critical piece of information because it tells us not only of course how tall the forests are
but how much above ground woody carbon they store.
Forests represent one of the biggest carbon stocks on the Earth's surface.
And if we cut down and burn forests, we essentially are pushing more carbon into the atmosphere.
And if we allow those forests to regrow, we are sucking that carbon out of the atmosphere.
But we don't know right now how much carbon is where in Earth's forests
because we've never had that third dimensional measurement of Earth's forests
which is so tightly linked to its carbon content.
Narrator: Using tree height not only helps scientists track how much carbon is getting released into the air
but can also be used in other ways.
Nancy Glenn: Tree height is really important for us. As it is we're interested in knowing how tree height is affected
by increased CO2 or increased temperatures, or decreased temperatures.
And that gives us an indicator for making future predictions about trees in the future.
We're interested in is that trees and the differences in tree heights
provides some level of what we call structural diversity.
And structural diversity can be really really important for the health of an ecosystem.
As well as provide habitat for a variety of different types of animals.
So we're using NASA resources, NASA airborne data as well as satellite-based data like ICESat.
Narrator: Many Earth observing satellites such as Landsat can only see a top down view of Earth.
*camera shutter**camera shutter**camera shutter*
Narrator: This information comes in the form of two-dimensional images
made up of pixels between the size of 30 meters squared to 500 meters squared.
But now with GEDI on board the International Space Station and the launch of the ICESat-2 satellie in 2018,
scientists are able to see height added to this top down view of Earth.
By taking and submitting tree height observations, citizen scientists and students can help
scientists and researchers.
Not just by providing measurements from different ecosystems, but by providing a different type of data.
What seems like such a small piece to contribute, can help scientists across the world.
Laura Duncanson: The GLOBE Observer tree observation essentially let people all over the world
measure tree heights and give us that information where we can't go into every single forest ourselves as a small group of scientists.
Nancy Glenn: From a scientist's perspective, but also as somebody who participates in citizen science.
It's a great intersection.
The more data the better.
But also, the connection, right? Is this connection between scientists and the community. And
scientists understanding what's important to our communities.
And being able to engage and learn from one another.
Claudia Carabajal: There is a large part of collaboration
between the instrument scientists and everybody working on every aspect of the ATLAS instrument.
And the mission scientist and his deputy and everyone else, and all the universities.
Citizen science is really important to get the community involved.
It motivates everybody to be more informed about the science.
And also perhaps motivate a crowd new scientists.
Nancy Glenn: All of this is important because one, it's the pursuit of
answering questions about our natural environment.
Our natural environment is changing very rapidly.
Nathan Kurtz: A tree height measurement that's taken by citizen scientists could be useful for us.
Nancy Glenn: It's really important for us to monitor what is here now.
So we can document that, but also use that in models to predict what might be here in the future.
Narrator: To learn more about GLOBE Observer
check out the website at
observer dot globe dot gov
And download the app to start taking your own observations today.
Explore Earth
NASA
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