Global warming caused vital Atlantic Ocean currents to collapse just before the last ice age, a new study suggests.
The weakening currents triggered a cascade of effects, resulting in a dramatic cooling of the Nordic Seas — the Greenland, Iceland and Norwegian seas — while the surrounding oceans grew warmer. And scientists say we could be heading toward the same thing again, as the world warms with climate change and temperatures race closer to the levels that existed before the last ice age.
"Our study is indeed alarming regarding what we might be heading to," study lead author Mohamed Ezat, an associate professor and paleoceanographer at The Arctic University of Norway, told Live Science in an email.
The Last Interglacial period (130,000 to 115,000 years ago), which occurred between the previous two ice ages, was a relatively warm stage of Earth's history characterized by higher temperatures, higher sea levels and smaller ice sheets than we see today. Climate scientists say the Last Interglacial provides an analogue for the near future if countries fail to slash greenhouse gas emissions, with temperatures reaching 1.8 to 3.6 degrees Fahrenheit (1 to 2 degrees Celsius) above preindustrial levels.
"The time period we investigated, the Last Interglacial, is an interesting and very timely period to study," Ezat said. "We found that about 128,000 years ago, enhanced melting of Arctic sea ice had a significant effect on the overturning circulation in the Nordic Seas."
Nordic Sea currents play a critical part in a wider system of Atlantic Ocean currents called the Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream. The AMOC is essential for warming the Northern Hemisphere and functions like a giant conveyor belt, with warm waters from the Southern Hemisphere riding northward on the ocean surface and then cooling and plunging to the bottom in the North Atlantic to travel back south.
Melting ice in the Arctic can significantly impact the AMOC, because fresh water pouring into the North Atlantic dilutes surface waters, preventing them from sinking to the bottom to form deep currents. Research shows the AMOC is already slowing down as a result of global warming, and scientists say the system could grind to a halt in the coming decades.
Earlier this month, 44 leading climate scientists rang the alarm bell on the AMOC in an open letter addressed to the Nordic Council of Ministers, an intergovernmental forum that promotes cooperation between the Nordic countries. The letter outlined the risks linked to an AMOC collapse, including major cooling in the Northern Hemisphere and catastrophic shifts in tropical monsoon patterns.
Climate models suggest the AMOC could collapse before 2100, but there are huge uncertainties in predicting the timescales. "Looking at the distant past of the Earth's climate history in particular when it was warmer than today can reduce such uncertainties," Ezat said.
For the new study, Ezat and his colleagues analyzed new and existing data from sediment cores from the Norwegian Sea. They compared these data to similar information from North Atlantic sediments to reconstruct the sea ice distribution, sea surface temperature, salinity, deep ocean convection and sources of meltwater during the Last Interglacial.
The results, published Oct. 27 in the journal Nature Communications, suggest Arctic meltwater blocked the formation of deep-ocean currents in the Norwegian Sea during the Last Interglacial. This considerably slowed the southward flow of the AMOC, in turn slowing the engine that brings heat to the Northern Hemisphere.
"In brief, we found cooling in the Nordic Seas that we were able to link to a warming global climate and enhanced melting of sea ice," Ezat said.
The study highlights what could happen to the AMOC in the near future, Ezat said. Satellite observations show a drastic decline in Arctic sea ice over the past four decades, and scientists say ice-free summers will likely take hold by 2050. These will have major consequences for the AMOC.
"It sends out another reminder that our planet's climate is a delicate balance, and that climate action is an emergency," Ezat said. "We know that severe weakening of the AMOC isn't unlikely, and if it happens it will have serious implications [for] the high latitude regions and beyond."
Its strange to me, they teach us in american high schools that the ice age ended a long time ago, and never teach us about things like "inter glacial" periods. But become a specialist such as a geologist or something similar and you learn about it pretty quick.
All I see here is our leaders boldly claiming that its man made, when there is no proof of that.
Was it mankind warming the environment 115,000-130,000 years ago? How can they so boldly claim mankind is going to cause this event if it happens on a fairly repeatable, predictable pattern? Real humdinger I guess.
Before you scream fake, at least try to attempt to contemplate the information here. I know people dont believe in ice cores, but they only tell half the story.
For the new study, Ezat and his colleagues analyzed new and existing data from sediment cores from the Norwegian Sea. They compared these data to similar information from North Atlantic sediments to reconstruct the sea ice distribution, sea surface temperature, salinity, deep ocean convection and sources of meltwater during the Last Interglacial.
https://en.wikipedia.org/wiki/Marine_sediment
Rates of sediment accumulation are relatively slow throughout most of the ocean, in many cases taking thousands of years for any significant deposits to form. Sediment transported from the land accumulates the fastest, on the order of one metre or more per thousand years for coarser particles. However, sedimentation rates near the mouths of large rivers with high discharge can be orders of magnitude higher. Biogenous oozes accumulate at a rate of about one centimetre per thousand years, while small clay particles are deposited in the deep ocean at around one millimetre per thousand years.
Sediments from the land are deposited on the continental margins by surface runoff, river discharge, and other processes. Turbidity currents can transport this sediment down the continental slope to the deep ocean floor. The deep ocean floor undergoes its own process of spreading out from the mid-ocean ridge, and then slowly subducts accumulated sediment on the deep floor into the molten interior of the earth. In turn, molten material from the interior returns to the surface of the earth in the form of lava flows and emissions from deep sea hydrothermal vents, ensuring the process continues indefinitely. The sediments provide habitat for a multitude of marine life, particularly of marine microorganisms. Their fossilized remains contain information about past climates, plate tectonics, ocean circulation patterns, and the timing of major extinctions.[1]
The science is pretty solid on this one.
Not really. We're talking about comparing ice core temperature estimates, which give about a mm of data for every thousand years of time, and modern digital temperature measurement. How can you even say that current temperatures are above pre-industrial levels if that wasn't even a thousand years ago? They're comparing apples to oranges and saying, in essence "Apples are only green when they're unripe, thr good ones are orange".
Sediment cores also completely fail to account for instantaneous phenomenon, like solar flares, asteroid impacts, and volcanic eruptions, which are significant factors to global climate.
As for the interglacial stuff, he's talking about a single data point. You can't make serious predictions from a single data point.
Add to that all the "scientists say", "evidence suggests", and "models show" language and they make a pretty weak case.
AGW doesn’t exist. You’re literally calling a Roland Emmerich film real. Fuck off, shill.
Randall Carlson
FTFY
There's absolutely no mention of sunspot data or solar storms. The sun drives our climate, not carbon. Emissions-based planetary warming is a HOAX.