Whales and Changing Sea Ice
What Scientists Think
1978, scientists have used satellites to track sea ice and other factors
in the Arctic. This long-term data has let them observe dramatic changes
they could not have seen in a short time period. Here are some of their
findings and theories.
Sea Ice is Melting!
- In the
past few years, Arctic sea ice has melted unusually early in the spring.
In fact, in the 2004-2005 winter season, it began to melt earlier than
in any other winter on record. In the gray whale's feeding and breeding
grounds in the Bering sea, it's melting about three weeks earlier than
ice coverage and thickness has dropped steadily during the last few
decades. Now the minimum cover is the lowest ever measured
since sea ice cover records were kept.
the past few decades, annual average temperatures in the Arctic have
increased at almost twice the rate as in the rest of the world.
ice is light-colored, so it reflects most of the sun's energy
(heat) back into space. But as the sea ice melts, the darker water absorbs
much of this energy. This warming water melts the ice even faster!
say that global climate change is the main cause of
the warming of the Bering Sea. (Another is weaker cold north winds that
blow across the sea.)
activity, such as burning fossil fuels, is a key cause of global
warming. It releases tons of carbon dioxide and other "greenhouse
gases" into the air. These cause the Earth to trap more of the
sun's warmth than it otherwise would.
Could it Affect Gray Whales?
north Bering Sea is one of the world's richest feeding grounds for whales,
walruses, and sea birds. Scientists only know some of the ways
in which climate change affects marine life. After all, it's a complex system.
Everything is linked to everything else! Here are some of their observations.
What other ideas did you come up with?
each photo to enlarge.
An adult gray whale will swallow about 77 tons of food
in the Arctic. That's a LOT of amphipods, which are only a few
food available — Microscopic sea plants called phytoplankton
are the starting link in the Arctic sea food
chain. Each spring as sunlight hours increase, they start to make food
and grow under the ice. They grow so fast that they crowd each other
out by June. As they suffocate and die, they fall to the muddy bottom.
This creates a nutrient-rich food layer. Bottom-dwelling animals such
as amphipods — the main food for gray
whales — feed on that layer. But as ice melts earlier and water
warms, the phytoplankton's life cycle is disrupted. The result? Less
food for every animal in the food chain!
competition — Near-freezing water in
the northern Bering Sea once kept bottom-feeding fish like halibut and
flounder farther south in warmer waters. But as sea floor temperatures
have risen, the fish have moved farther north. There they compete for
food with larger animals, such as walrus, sea ducks, and whales.
moving north — Researchers say that
gray whales are adjusting to the changes by heading further north. There
they feed in colder waters of the Chukchi Sea. But those shallow waters
only go so far! Once whales get to the deep waters off the continental
shelf, they won't be able to find food. (Other animals, such as bearded
seals, may not be able to adjust enough to survive.)
the gray whales shift northward, they move near the territory of the
bowhead whale, which feeds offshore. Alaskan natives hunt and eat the
bowhead. They are concerned that the more aggressive gray whale may
interfere with the quieter bowhead. Hunters are noticing
that many gray whales are sticking around all winter rather
than making the journey south!
Deeper: You Be the Judge!
Read these articles. As you do, highlight, underline, or keep lists of
of changes in sea ice and climate
about why these changes are happening (use one color for facts and another
about how these changes affect gray whales (use one color for facts
and another for theories/opinions)
opinion on what you think we could do to slow down these changes.