Arctic sea ice is disappearing
Ted Scambos says that could mean big changes for the whole planet.
Ted Scambos is lead scientist at the National Snow and Ice Data Center in Boulder, Colorado. In 2005, his research showed that sea ice in the Arctic covered less area than had been observed since 1978, when satellite measurements began. Earth & Sky’s Jorge Salazar spoke with Dr. Scambos about the dramatic shrinking of Arctic sea ice in 2005.
Salazar: Could you describe some of the findings of the sea ice study you’ve just completed?
Scambos: We have a pretty good record from satellites of how sea ice grows and shrinks every year. We have a record that goes all the way back to 1978. That’s pretty clear.
And when we look at the trends in that record for the summertime, in the last four years, we’ve seen four really significant low minimum extents. In other words, ice has really retreated for the last 40 years. And this year, in particular, it’s retreated quite a bit.
And this year, in particular, it retreated particularly from the Siberian coast. There’s a huge area of open water off the coast of Siberia that’s unprecedented. It’s never retreated this far before.
We think this retreating sea ice is part of the process of climate change. We’re concerned that we’re going to see a change, a rapid change, in the Arctic sea ice. It’s even more concerning because the sea ice is a major component of the Earth’s climate system.
Salazar: So, how big a reduction in sea ice are we talking about?
Scambos: Usually, at the end of the summer, it’s around seven million square kilometers. That’s the size of a small continent. Right now, what we’ve seen is a 20% loss of that sea ice, in the summer. It’s much larger in the winter, and it will grow again in winter. What we’ve seen is a 20% loss, or an area equivalent to twice the size of Texas.
So, its a fairly significant change, And it’s a change that appears to be accelerating in the last few years, in terms of how steep the slope is when you fit a trend line through these last few years of September minima.
Salazar: When you mention a 20% reduction, what is that in contrast to?
Scambos: Every year, the ice grows and shrinks. We’re keeping track of how much ice there is right at the end of summer. We keep track of that point, and then we plot that point over time. The last four years have seen a pretty low minimum extant, much lower than we’ve seen over the last 20 years in the last part of the 20th century. It’s low, even relative to what records we have going back until the year 1900.
Having a 20% loss in sea ice is probably just the beginning of a long–term trend, getting to the point where, eventually, in summer, we will have no sea ice up in the Arctic ocean.
Salazar: How confident are you of these findings?
Scambos: There’s really good consensus that Arctic ice is changing, and that the Arctic is much warmer than it used to be.
In the Arctic, the effects of climate change are amplified. They’re amplified because ice and snow, as they start to melt, begin to absorb more energy from the sun. They get darker, and so the pace of melt is accelerated. If you have melt starting early in the season, you wind up with a lot more melting and a lot more loss of ice in the season.
There’s good consensus on the area of the changes of the ice, there’s good consensus on the fact that the Arctic is getting warming. What there isn’t good consensus on is exactly what it means for the rest of the world’s climate. What we know is that the Arctic is a major driver for Earth’s weather cycle. Heat at the equator and cold at the poles is a major force driving the winds and weather on Earth. What we’re doing, slowly, is seeing a change in the amount of energy that’s going to be absorbed by the Arctic. It will be much darker it there’s less sea ice, so more heat will be absorbed rather than reflected.
Exactly what effects will occur around the world in terms of weather and climate? It’s unclear at this point. Our models show that there would be an increased tendency towards drought in certain areas. I think in general I think that we’ll see a lot more humidity in the atmosphere. We might see a milder, longer autumn and a shorter winter in the long run, all because of the loss of Arctic ice and the thinning of Arctic ice over the next several decades.
Salazar: How likely is it that this decline isn’t just a blip, some sort of temporary dip in the ice coverage that can be made up later?
Scambos: In the past four years, we’ve seen different weather patterns, yet we’ve still wound up with very low sea ice extant at the end of those years. What it’s telling us is that there’s no one weather pattern, there’s no trend that is going to be changed in the near future that will lead to a growth in Arctic sea ice.
Every pattern that we’ve seen since 2002 has led to low Arctic ice. The one thing that’s been consistent in all four years is that the Arctic has been a lot warmer.
As snow begins to melt, you get more and more energy absorbed by the snow. And you get less and less sea ice at the end of the summer. We think that these feedbacks are starting to take hold and that we’re going to see an accelerated decline in sea ice.
Salazar: Earlier in your description you attribute the ice change to climate change. Could you describe how that is so?
Scambos: The Arctic has gotten a lot warmer, much more so than most of the rest of the U.S. or Europe or Asia. It’s seeing an accelerated climate change because snow and ice in the Arctic tend to be close to the melting point. A slight change in temperature means a fundamental change for the Arctic.
Eventually, you’re going to see no snow and either dark land or dark ocean in its place. So, there are these amplifying effects in the Arctic that lead to a more rapid climate change.
Now because the Arctic and the North Pole itself is such an important part of our weather system, it’s likely that the trends that we see are going to be very profound in terms of global weather change. If you think about holding the globe in front of you and looking at the North Pole, most of that whole area over the top of the Earth is bright white and reflecting energy away from the Earth. But if you turn that into a dark surface, you’re going to see a lot more energy absorbed there and a profound change in the weather systems.
I think this a more important, a more likely cause for concern than sea level rise, because we’re able to adapt to sea level rise at the rates that it’s likely to occur, a meter in a century. It’s not that hard to get ready for. But with change in the Arctic ice, we’re unsure exactly what the weather systems will be in response to this big change in the Earth’s energy balance.
Salazar: Why don’t we see a corresponding shrinkage in Antarctic sea ice?
Scambos: You’re right, there aren’t changes that are similar. But the changes that occur there are thought to be due to global warming also.
What we’re seeing in the Antarctic is more snowfall, and that’s because unlike the Arctic, the Antarctic is quite a bit below the freezing point even in summer. It’s very, very cold there, colder than the Arctic. So, if you warm the Antarctic climate a little bit, what you get is more moisture in the air and more snowfall. The changes that we’re seeing over most of the continent are a slight thickening due to increased snowfall, and a slight thickening of the sea ice around the Antarctic because of more snowfall.
So, it’s the same root cause. We think that global warming is the root cause behind both thickening in the Antarctic because of more snowfall, and thinning in the Arctic.
Salazar: Thanks again for your time today. Is there a take–home message from these findings?
Scambos: These are observational results. There’s really little room for debate. We’re seeing the loss of sea ice, the cover of the Earth’s ocean in the Arctic. Those changes are definitely going to have a big effect on climate. We just can’t be certain of what that effect will be.
Salazar: Thank you, Dr. Scambos.
