My name is Jen Kay, and I'm the professor at the University of Colorado. In this
video we introduce feedbacks that are important in the Arctic climate system.
Hi, I'm Ariel and I'm a graduate student working with Jen. I study Arctic clouds and sea ice. I'm here in Churchill, Manitoba which is a really
cool little town on the coast of the Hudson Bay. Polar bears spend time nearby
while they wait for sea ice to refreeze each year in the fall. In fact, during
late fall the nine hundred human Churchill residents share the tundra
with about nine hundred polar bears. Now to talk about neighbors you'd want to
get along with. The nearby Hudson Bay has sea ice on it during winter, sea ice is
bright, white, and reflective. The high reflectivity of sea ice means that has a
high albedo, which is simply a measure the reflectivity of a surface. For
example if a surface reflects 50% of the sunlight that hits it then that surface
has an albedo of 0.5. Albedo ranges from zero, which is reflecting no incoming
sunlight to one, reflecting all incoming sunlight . The albedo of sea ice is about
point six on average, snow on top of the sea ice increases the albedo to 0.9. A
lot of sunlight can get reflected from fresh snow which is why you wear
sunscreen and goggles when you ski your snowboard in Colorado. Snow and sea ice
maintain a pretty high albedo for the Arctic surface but that albedo changes
as snow and sea ice cover change. Every year in the Arctic snow and sea ice start
melting in the spring and continue melting through the early fall. When sea
ice melts completely the dark ocean is exposed
since the ocean underneath is very dark it has a really low albedo, point zero
six. The ocean only reflects away about six percent of incoming sunlight so it
absorbs a lot of energy from the Sun. when the surface ocean absorbs energy it
warms and more sea ice melts. As more sea ice melts, more dark water is exposed.
more open water in turn leads to more sunlight being
absorbed by the ocean. As the surface ocean absorbs more sunlight, more sea ice
melts—and you get the picture . This whole process is called the surface albedo
feedback. Feedbacks are a key concept to understand in the climate system.
feedbacks can be positive and negative. let's say the climate system is warming
a positive feedback occurs when factors further increase that warming a negative
feedback on the other hand occurs when factors reduce that warming. We are
particularly interested in Arctic feedbacks because over the last three
decades the Arctic has warmed three times more than the global mean, the
evolution of the Arctic climate system is influenced by many positive and
negative feedbacks. The surface albedo feedback is a positive feedback that
further increases Arctic warming and sea ice loss. What are the negative feedbacks
in the Arctic? specifically is there some sort of negative feedback that could
slow down sea ice loss? to talk about a negative feedback in the Arctic we're
going to move up into the atmosphere and talk about clouds. because clouds are
bright they have a similar albedo to snow-covered sea ice about point eight
for clouds and remember about point nine for snow-covered ice. in the summer when
the surface albedo feedback is strongest because the days are long and there's
lots of sunlight, forming clouds over newly open ocean could replace one lost
bright surface, the sea ice, with another clouds, thereby maintaining a fairly high
albedo for the Arctic surface and reflecting sunlight away from the ocean.
however in my research I found no evidence that Arctic clouds form in
response to sea ice loss during the summer. summer clouds can't be relied
upon to reduce the strength of the surface albedo feedback and slow the
rate of Arctic sea ice loss. the Arctic climate system is a complicated place
with many positive and negative feedbacks. we learned about the
importance of feedbacks the positive surface albedo feedback that we have
evidence for, and a potential negative feedback we aren't seeing
evidence for. the Arctic has warmed and is projected to warm a lot more because of
its particularly strong positive feedbacks.