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(Santa Barbara, Calif.) – As an indicator of the impacts of climate change, Arctic sea ice is hard to beat. Scientists have Observed the Frozen Polar Ocean Advance and Retreat at the Global Ocean Circulation, Surrounding Habitats and Ecosystems, Food Sources, Sea Levels and More.
Despite efforts to make model simulations more closely mirror actual observations of Arctic sea ice melt, however, a gap has opened up.
"Based on this phenomenon," said UC Santa Barbara climate scientist Qinghua Ding, an badistant professor in the campus's Earth Research Institute. The consensus of the climate science community, he said, is leaning towards the idea that the discrepancy is due to flawed modeling. "It's something like the model," he explained.
Ding and his group disagree. In a study titled "Fingerprints of internal drivers of Arctic sea ice in observations and model simulations," published in the journal Nature Geoscience, the group says the models are just fine. About 40 to 50 percent of sea ice over the last three decades, they argue, is attributable to significant but as yet little-understood internal drivers – as far as they go.
"Actually, we are comparing apples to oranges," Ding said of the discrepancy between real-time observation and simulated Arctic ice melt driven by anthropogenic forcing. The average of models, it is explained, accounts for the effects of a small sample temperature, humidity, atmospheric pressure, and other factors both locally and connected to other phenomena elsewhere on Earth. Such higher-frequency events often show up as noise in the repeated, individual runs of the simulations as scientists look for general long-term trends.
"Bradley Markle, a postdoctoral scholar in Ding's research group. "If you take 20 or 30 runs of a model, they will each have their own random noise, but they will cancel each other out." The resulting value is the average of all the simulation runs with random variability. But that random variability may also be impacting on the value of the signal.
Due to their nature, Arctic ice melt will appear to slow down or even reverse, but in the bigger picture, climate scientists still see the eventual complete melting of Arctic sea ice for part of the year .
"There are so many reasons we focus on Arctic sea ice," said Ding, referring to a time when the sea will not be longer. frozen frontier it has been even in the summer.
"Right now, the prediction is about 20 years," Ding said. More than just a climate issue, he continued, the ice-free summer is also a societal issue, given the effects on fisheries and other food sources and habitats that benefit from a frozen polar ocean. One of the things this discrepancy between simulation and observation indicates, he said, that the predictions about when this ice-free summer occur will be with some acknowledgment of the effects of internal variabilities.
"There's a lot of uncertainty badociated with this time window," Ding said. "As we consider internal variabilities plus CO2 forcing, we should be more cautious about the timing of the ice-free summer. "
For Markle, this situation is important in terms of long-term climate trends versus short-term observations. Over the course of our daily life, we experience a significant increase in the temperature of our environment.
"Likewise, year-to-year temperature variability, such as may be badociated with these tropical variations, may be several times in annual average temperature in a specific area," said.
An El Niño Southern Oscillation (ENSO), the constant tipping between the El Niño and the counterpart the world. More extreme ENSO-driven weather behavior is expected in the Earth's climate equilibrium in the face of an average global temperature increase of even a couple degrees.
"Just for reference, 20,000 years ago, there was an ice sheet covering most of Canada during the last ice age – that was a four- or five-degree annual average temperature change," Markle said, "but it's a huge difference."
Arctic sea ice, particularly those that originate in the warm, wet tropics.
"We're mostly interested in the early 2000s to the present day," said graduate student Ian Baxter, who also works with Ding. It is known, that the effects of the Arctic are not longer in the region and spread to mid-latitudes – often in the form of cold weather. The group is interested in how the Arctic affects the Arctic.
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