- Sea ice can act as an agent of climate change on a variety of timescales and spatial scales—it’s not just a passive responder to change.
- The Little Ice Age may have arisen “out of the blue,” from internal variability within the climate system, rather than in response to an external push from volcanic eruptions or other factors.
- A far-flung pulse of sea ice may have contributed to the demise of the Norse colonies in Greenland in the 14th and 15th centuries.
A new study finds a trigger for the Little Ice Age that cooled Europe from the 1300s through mid-1800s, and supports surprising model results suggesting that under the right conditions sudden climate changes can occur spontaneously, without external forcing.
The study, published in Science Advances, reports a comprehensive reconstruction of sea ice transported from the Arctic Ocean through the Fram Strait, by Greenland, and into the North Atlantic Ocean over the last 1400 years. The reconstruction suggests that the Little Ice Age—which was not a true ice age but a regional cooling centered on Europe—was triggered by an exceptionally large outflow of sea ice from the Arctic Ocean into the North Atlantic in the 1300s.
While previous experiments using numerical climate models showed that increased sea ice was necessary to explain long-lasting climate anomalies like the Little Ice Age, physical evidence was missing. This study digs into the geological record for confirmation of model results.
Researchers pulled together records from marine sediment cores drilled from the ocean floor from the Arctic Ocean to the North Atlantic to get a detailed look at sea ice throughout the region over the last 1400 years.
“We decided to put together different strands of evidence to try to reconstruct spatially and temporally what the sea ice was during the past one and a half thousand years, and then just see what we found,” said Martin Miles, an INSTAAR researcher who also holds an appointment with NORCE Norwegian Research Centre and Bjerknes Centre for Climate Research in Norway.
The cores included compounds produced by algae that live in sea ice, the shells of single-celled organisms that live in different water temperatures, and debris that sea ice picks up and transports over long distances. The cores were detailed enough to detect abrupt (decadal scale) changes in sea ice and ocean conditions over time.
The records indicate an abrupt increase in Arctic sea ice exported to the North Atlantic starting around 1300, peaking in midcentury, and ending abruptly in the late 1300s.
“I’ve always been fascinated by not just looking at sea ice as a passive indicator of climate change, but how it interacts with or could actually lead to changes in the climate system on long timescales,” said Miles. “And the perfect example of that could be the Little Ice Age.”
“This specific investigation was inspired by an INSTAAR colleague, Giff Miller, as well as by some of the paleoclimate reconstructions of my INSTAAR colleagues Anne Jennings, John Andrews, and Astrid Ogilvie,” added Miles. Miller authored the first paper to suggest that sea ice played an essential role in sustaining the Little Ice Age.
Scientists have argued about the causes of the Little Ice Age for decades, with many suggesting that explosive volcanic eruptions must be essential for initiating the cooling period and allowing it to persist over centuries. One the hand, the new reconstruction provides robust evidence of a massive sea-ice anomaly that could have been triggered by increased explosive volcanism. On the other hand, the same evidence supports an intriguing alternate explanation.
Climate models called “control models” are run to understand how the climate system works through time without being influenced by outside forces like volcanic activity or greenhouse gas emissions. A set of recent control model experiments included results that portrayed sudden cold events that lasted several decades. The model results seemed too extreme to be realistic—so-called Ugly Duckling simulations—and researchers were concerned that they were showing problems with the models.
Miles’ study found that there may be nothing wrong with those models at all.
“We actually find that number one, we do have physical, geological evidence that these several decade-long cold sea ice excursions in the same region can, in fact do, occur,” he said. In the case of the Little Ice Age, “what we reconstructed in space and time was strikingly similar to the development in an Ugly Duckling model simulation, in which a spontaneous cold event lasted about a century. It involved unusual winds, sea ice export, and a lot more ice east of Greenland, just as we found in here.” The provocative results show that external forcing from volcanoes or other causes may not be necessary for large swings in climate to occur. Miles continued, “These results strongly suggest…that these things can occur out of the blue due to internal variability in the climate system.”
The marine cores also show a sustained, far-flung pulse of sea ice near the Norse colonies on Greenland coincident with their disappearance in the 15th century. A debate has raged over why the colonies vanished, usually agreeing only that a cooling climate pushed hard on their resilience. Miles and his colleagues would like to factor in the oceanic changes nearby: very large amounts of sea ice and cold polar waters, year after year for nearly a century.
“This massive belt of ice that comes streaming out of the Arctic—in the past and even today—goes all the way around Cape Farewell to around where these colonies were,” Miles said. He would like to look more closely into oceanic conditions along with researchers who study the social sciences in relation to climate.
Reference: “Evidence for extreme export of Arctic sea ice leading the abrupt onset of the Little Ice Age” by Martin W. Miles, Camilla S. Andresen and Christian V. Dylmer, 16 September 2020, Science Advances.
Camilla S. Andresen, of the Geological Survey of Denmark and Greenland, and Christian V. Dylmer, of MMT Sweden AB, were coauthors of the study.
What about the disturbances in the warm ocean currents?
It’s about time for this to happen again, one would hope. More ice is what we need about now.
I found this article to be very interesting in many ways. One main one being climate change and how it can be triggered… Now please take the time and overlay you chart with the current extended decline in activity. You might find that the two charts look very much alike. Lower solar activity = less solar energy = more cosmic rays changing weather patterns = final results being a cooler planet and mini ice age… I believe, and have believed since 2000 that is what is happening…
It’s the Sun, stupid.
Regarding previous comments:
No, a solar minimum did NOT cause the LIA. The solar minimum came much later than the beginning of the cool period. Hundreds of years later.
And NO, the Sun is not the cause of global warming. Solar activity has declined since 1960.
During that same time frame, about 2/3 of the warming since 1880 has happened.
The science of the greenhouse gas effect says that there should be warming of the troposphere and cooling of the stratosphere.
That is exactly what has been observed. And that is a signature of the greenhouse effect, and NOT of Solar effect.
If the sun was the cause of the warming, both layers of the atmosphere would heat up.
If the sun was the cause of the warming, days would be warming more than nights. But what is being observed is nights warming more than days, which is what should happen if greenhouse gases are causing warming.
Claims that anything but human caused greenhouse gas emissions, especially CO2, are not the cause of global warming are nonsense.
That CO2 traps heat in the troposphere, and how it does it, has been understood since the late 1850s.
And here is what we have done.
We are increasing atmospheric CO2 100 times faster than the fastest that nature has done in At Least the last 450,000 years and almost certainly in the last 800,000 years or more.
Humans increased CO2 by over 80ppm in 60 years
Humans increased CO2 by 130ppm in 140 years
Nature caused CO2 increases over the last 450,000 years, from ice core data
80ppm increase — took 50,000 years
110ppm increase — 25,000 years
120ppm increase — 20,000 years
60ppm increase — 20,000 years
90ppm increase — 15,000 years
100ppm increase — 24,800 years
The numbers for 800,000 years would be similar, based on a graph, from ice core data going back that far.
The result is that the planet is warming at least 10 times faster than when it came out of the last ice age. It took about 10,000 years to warm by about 5 C, with temps peaking about 8,0000 years ago. The world has now warmed by 1 C in about 140 years. That comes to 14 times faster.
8,000 years ago – sorry about the typo
What a strange coincidence that the Vikings set up shop there, and then promptly got iced out. If it wasn’t for bad luck…
Ice just doesn’t appear in the hot tropics. This chart nearly and directly corresponds with the solar cycles. Particulary the Grand Solar Minimal(G.S.M.) that ‘most likely’ triggered the cool off resulting in the Great Winter during the 1600’s.
The stalling of the Atlantic circulation was posited by Kim Stanley Robinson ages ago. Saying that Ice Ages happen without external forcing is ludicris. It happens cyclically like clockwork every 12 to 13k years, just as say we carousel up into the galactic current sheet which may be the torus of a torus jet around the black hole at the centre. All plausible. This article is either woefully behind the times or designed to let people down slowly as the info becomes less and less avoidable, like when Boston is under 20ft of snow. Good luck everyone. Time to start canning thise pickles.
I remember in high school earth
science telling our teacher that it sure looked like South America and Africa were fitted together at one time.We were told that science said no To those of you in your ivory towers sometimes you are wrong.Enough said.