From an observational stand point we're at a sweet spot
where we can see many different aspects of the changing ice cover
and so that the problems are then
moving toward understanding what we see changing.
It is pretty clear that we're gonna understand what the ice is doing.
I think that observational glaciology in terms of remote sensing
is a very data rich field now
compared to 1972 when you had a few images.
So we are beginning to get a historical record of the speeds of glaciers
and so we can watch how rapidly that surface is lowering
as things speed up or where it's thickening
and where the surface is actually coming up
or where ice is actually thickening on land.
With this record we can go in and look at the speeds of ice flow
over decades and how it's been changing
The reaction I get from other people that study glaciers
is that I watch these videos too fast.
I like to see the fluid nature of the ice.
It lets you see the ice on the land
as sort of this very active participant in what's going on.
One of the places that I like to look at in this particular video of Hubbard
is if you look just to the upper-left off the five kilometer scale bar
you can watch the edge of the glacier just spread across the the river bed
that's coming out of the glacier that's adjacent to it.
And it just moves, it moves trees,
it moves all sorts of material every single year, just advancing.
So this video that shows the Walsh glacier on the top
and the Logan glacier on the bottom,
these are huge glaciers. They're the order of four kilometers wide or so.
What we see as we loop through it is that the flow in both of these
sits there for years and then it will undergo
a pulse of faster motion and then sit there again.
What strikes me about this image of the Malaspina
is that you can really see its nature,
which is that it's a large puddle of ice.
You've got huge glaciers that are flowing down
out of a really high mountain range.
And these big glaciers reach the coastal plain
and the ice just spreads out in this big puddle,
like you've taken a bottle of syrup,
and just dumped it in the middle of a plate.
The Malaspina is sort of that big pile of syrup.
The other thing that you see is that
the ice coming in will head either to the left or the right of center,
for a while, and it will string out those moraines
so that they get bent into these loop shapes.
And you know it wasn’t until I saw this video
that I felt like I had a good understanding of just
what was producing these amazing loops in the moraines.
In compiling this Landsat record,
from Landsat 1 in 1972 up through today,
I've gone through year by year and I've tried
to pick out the latest melt season image I can.
So the white snow of winter is gone and you can see the detail
and the flow stripes and the crevasses in the ice.
And build annual mosaics that give us an
image of all of the ice in Alaska and the Yukon.
And when those are all lined up - all 48 of them are lined up
and played as a movie - we can see the behavior
of the ice over nearly half a century.
Having such a long record allows us to discern long-term trends
and separate them from the kind of behavior you might get
with a couple warm or a couple of cold years.
To have a persistent observational capability
that's been in place ever since the first Landsat was launched,
it really gives us a much better view of this
really rapidly changing part of our planet.