Are glaciers behind perplexing shift in paleoclimate Ice Age patterns?

In early August, at the Goldschmidt Conference on geochemistry, a team of scientists from Columbia University presented evidence from seafloor cores that suggest that a million years ago ice sheets in the Northern Hemisphere began sticking to their bedrock. The team proposes that as the glaciers grew thicker, it led to a global cooling that disrupted both the Atlantic Meridional Overturning Circulation (AMOC) and the ice age cycle. But how exactly might glaciers have been involved in this perplexing shift in paleoclimate ice age patterns?

As skeptics of anthropogenic climate change often note, Earth’s climate changes and has changed before. Aside from humans’ unabashed consumption of greenhouse gases, a wide variety of natural factors cause shifts in this complex system. For instance, scientists have long acknowledged how tiny changes in the Earth’s orbit around the sun, collectively known as the Milankovitch Cycles, drive the coming and going of ice ages. As the Milankovitch Cycles interact, the planet’s movements displace the incoming solar radiation across the globe, dramatically affecting the Earth’s climate system and the advancement and retreat of glaciers.

Glaciers in the North Atlantic, such as this one in the Johan Petersen Fjord of eastern Greenland, may have driven a global cooling a million years ago (Source: Ray Swi-hymn/Flickr).

For a while, ice ages were known to occur steadily every 40,000 years. However, a million years ago, that metronome inexplicably got off course. Instead of periods of intense glaciation occurring every 40,000 years, it shifted to every 100,000 years. But the likely culprit, the Milankovitch Cycles, hadn’t changed a million years ago. It didn’t add up.

And that’s not all. Around the same time, the massive AMOC— the conveyor belt that brings warm, shallow water to the North Atlantic, where it cools and sinks to the sea floor before returning south— nearly collapsed. Were these events related? If so, how and what was behind them?

These questions have perplexed scientists for years, as was apparent even at last month’s conference. But through an analysis of the chemical composition of basin-wide ocean sediment cores over several years, geochemist Steve Goldstein from Columbia University, who led the study presented at Goldschmidt, found unique shifts in isotopic signals that reflect a slower turn of the AMOC 950,000 years ago. 

For the present study, the team examined five more ocean cores, in addition to two analyzed earlier in the decade, that also demonstrated signs of a weak AMOC. The group believes two of the cores from the North Atlantic indicate possible triggers for the AMOC crisis. They suggest that such a slowdown could have rapidly cooled the North Atlantic region, in turn lengthening the ice age rhythm.

Peter Clark, a glaciologist at Oregon State University in Corvallis, has advanced this hypothesis as the only plausible explanation for many years, wrote Paul Voosen in Science last month. Three million years ago, a sustained warming period allowed for the build-up of thick soil in the Northern Hemisphere. Ice sheets would often collapse as the soil acted as an oiled buffer. But repeated glaciations wore down the warm protective layer and enabled glaciers to dig deeper into older rock that stabilized them and helped them thicken and advance.

Aerial shot of a large glacier in Greenland (Source: Leon Weber/Flickr).

But as exciting as the findings may be, not everyone is sold on the hypothesis. Climate scientist Amy Clement from the University of Miami told GlacierHub it sounded like an interesting concept, but she has problems with how the AMOC idea is applied in the modern climate. Clement explains how some argue that variations in the AMOC strength control the North Atlantic surface temperature on these multi-decadal timescales.

“The problems are (1) timescale and (2) magnitude. On these short timescales, the AMOC doesn’t seem to be the driver,” she noted to GlacierHub. “Instead we think the North Atlantic surface temperatures are controlled by external forcing (some natural, such as the sun and volcanoes) and some anthropogenic (such as greenhouse gases and aerosols).”

Others including Henrieka Detlef, a paleoclimatologist at Cardiff University in the U.K., told Science that while she accepts something important happened in the North Atlantic to lead to AMOC crisis, she has yet to see conclusive evidence that northern ice sheets were increasing in thickness prior to the AMOC slowdown.

Still, most agree that ice age rhythm shifts were likely caused by more than one trigger. The Columbia team is confident that thickening ice sheets in addition to other factors played a role in the perplexing transition. “The interactions between the different components of the Earth’s climate are elusive, but understanding them is crucial for reconstructing past changes,” Maayan Yehudai, part of the research group and a graduate student at Columbia, told GlacierHub. “We still have a long way to go as scientists before we can characterize them perfectly, but I think this is another important step forward on this account.”

The inevitable doom of Glacier Rush

In the game Glacier Rush, you help a narwhal eat as many fish as it can before getting inevitably crushed by sinking blocks of ice.
In the game Glacier Rush, you help a narwhal eat as many fish as it can before getting inevitably crushed by sinking blocks of ice.

I lost track of how many narwhals I killed.

Each time it was the same; a block of ice fell into the ocean, I thought I had given enough time for the narwhal to react and get out of its way but again, the ice hit it, its eyes turned into little x’s and the narwhal sank to the bottom of the ocean.

I wasn’t getting real narwhals killed, thankfully, but little cartoon versions of them in Glacier Rush, the new free game for iPhone and Android.

The game itself is simple enough; you drag your finger across the screen to guide a cartoon narwhal in between sinking blocks of ice (Ok, so it’s not the most scientifically minded time-waster), trying to eat as many fish as you can before your eventual demise.

The game shares more than a few similarities to the ultra-simple Flappy Bird, a game where your only goal is to fly a bird through as many pipes as you can. In both games, the premise and controls are simple, but life is short and the need to keep playing often overtakes better judgment.

Much like other mobile games like “Temple Run” or “Lane Splitter“, no matter how well you perform or how long your character lives, they will inevitably succumb to the game. After a while you start to feel sorry for the narwhals, especially the ones that only live long enough to eat a handful of fish. Normally, I can get to 18, but never more than 33, my top score.

A round of Glacier Rush never last more than a few seconds, but these addictive single-premise games quickly waste one minute, then five, then 10. My first session with Glacier Rush ended after about 20 minutes when I became determined not to quit until my narwhal ate 25 fish. I went through the usual distinct stages of playing: adjustment, zen state, desperation, fugue state, back to zen, and then, once I had my 25 fish, mastery.

The game’s makers probably didn’t intend any level of interpretation of Glacier Rush beyond an amusing distraction. The falling ice, the cute animal in danger, the North Atlantic setting all seem to point to something a little darker: the inevitability of climate change. No matter how long you play or what path through the icebergs you manage to steer the narwhal, the ice will get you.

Narwals are a “near-threatened” species according to the International Union for the Conservation of Nature. Falling ice is less of a danger to them than being hunted by humans, though that risk greatly increases as the sea ice breaks apart more and more.

That might be reading too much into it, but according to game programmer Jody McAdams, the average narwhal lifespan is 16 seconds. The game probably isn’t an elaborate commentary on the collateral damage caused by global climate change, but after a few too many rounds of playing Glacier Rush, it’s easy to think how one way or another, ice will get us in the end.