Terrawatch: the adventurous icebergs that trigger ice ages
How does an ice age start? We know that changes in the Earth’s orbit around the sun alter the amount of solar energy reaching our planet, but it has long been a mystery as to how this triggers such a dramatic change in the climate. A study shows that Antarctic icebergs may be responsible for tipping the balance.
Aidan Starr, from Cardiff University, and his team analysed sediments recovered by the International Ocean Discovery Program from the ocean floor south of South Africa. Within those sediments were tiny fragments of rock dropped by melting Antarctic icebergs. By studying the chemistry of the tiny deep-sea fossils found throughout the sediment core, the scientists were able to show that when climate conditions enabled icebergs to travel this far north they made the North Atlantic fresher and the Southern Ocean saltier.
Climate and ocean simulations revealed that this pulse of freshwater to the North Atlantic triggered changes in ocean circulation patterns that led to more carbon dioxide being pulled out of the Earth’s atmosphere, helping to plunge the planet into an ice age. The results, which were published in Nature, show that every glacial period over the last 1.6m years is associated with Antarctic icebergs straying farther north than normal.
That was it. That was the entire article. Something’s wrong here I thought, the Graun almost never publishes anything on climate without mentioning the dreaded climate crisis. There must be more to it than this. So I dug a little deeper into reports elsewhere of this recently published paper and sure enough, climate change does get mentioned, by the authors themselves in fact.
Professor Ian Hall, co-author of the study and co-chief scientist of the IODP Expedition, also from the School of Earth and Environmental Sciences, said: “Our results provide the missing link into how Antarctica and the Southern Ocean responded to the natural rhythms of the climate system associated with our orbit around the sun.”
Over the past 3 million years the Earth has regularly plunged into ice age conditions, but at present is currently situated within an interglacial period where temperatures are warmer.
However, due to the increased global temperatures resulting from anthropogenic CO2 emissions, the researchers suggest the natural rhythm of ice age cycles may be disrupted as the Southern Ocean will likely become too warm for Antarctic icebergs to travel far enough to trigger the changes in ocean circulation required for an ice age to develop.
Professor Hall believes that the results can be used to understand how our climate may respond to anthropogenic climate change in the future.
“Likewise as we observe an increase in the mass loss from the Antarctic continent and iceberg activity in the Southern Ocean, resulting from warming associated with current human greenhouse-gas emissions, our study emphasises the importance of understanding iceberg trajectories and melt patterns in developing the most robust predictions of their future impact on ocean circulation and climate,” he said.
I’ve been around the whole subject of climate change alarmism long enough to know how these guys’ minds work. The above passage is very subtly phrased such that it leaves it open for climate scientists to claim either that man-made global warming means that ice ages might never happen ever again because we have made the oceans too warm for Antarctic icebergs to drift far enough north to trigger them or we’ve warmed the Antarctic so much that it’s beginning to break up and massive icebergs drifting as far north as the Cape may trigger a future catastrophic ice age. They like to keep their options open.
Freshwater pulses into the north Atlantic have long been associated with a dramatic slowing of the AMOC and climate alarmists have used evidence of rapidly melting Greenland glaciers (allegedly caused by global warming) to argue that the region may reach a ‘tipping point’ where the AMOC (which includes the Gulf Stream) abruptly slows, plunging Europe and North America into an era of much colder winters. Not a full ice age, more akin to that which happened during the Little Ice Age. But then other scientists have argued that we narrowly missed a full glacial inception near the end of that period and it was only man-made GHGs which ‘saved’ us. So it’s clear, there’s room to argue that if AMOC is disrupted by a nasty South African variant iceberg which has travelled far north from the Antarctic (due to global warming fracturing the ice shelf) we may be in for some decidedly chilly weather.
The authors argue that this may not happen (as it apparently has happened at each previous glacial inception) because the icebergs which break off may not travel as far north as South Africa because the Southern Ocean will be too warm. Hence the planet may be ‘doomed’ to remain within a perpetual warm interglacial. But it’s not that warm in the seas around Antarctica at the moment – in fact, the Southern ocean surface waters have been cooling, especially over recent decades, contrary to scientists’ expectations.
Despite global warming, SSTs in the Southern Ocean (SO) have cooled in recent decades largely as a result of internal variability. The global impact of this cooling is assessed by nudging evolving SO SST anomalies to observations in an ensemble of coupled climate model simulations under historical radiative forcing, and comparing against a control ensemble. The most significant remote response to observed SO cooling is found in the tropical South Atlantic, where increased clouds and strengthened trade winds cool the sea surface, partially offsetting the radiatively‐forced warming trend. The SO ensemble produces a more realistic tropical South Atlantic SST trend, and exhibits a higher pattern correlation with observed SST trends in the greater Atlantic basin, compared to the control ensemble. SO cooling also produces a significant increase in Antarctic sea ice, but not enough to offset radiatively‐induced ice loss; thus, the SO ensemble remains biased in its sea ice trends.
Over the period 1982 to 2011, however, a cooling trend was recorded in surface waters in some parts of the Southern Ocean around the Antarctic continent, specifically in the area south of 55 degrees latitude. This cooling was strongest in the Pacific sector of the Southern Ocean, where the ocean surface cooled by around 0.1°C per decade, and the weakest in the Indian and parts of the Atlantic sectors.
So at the moment, there is not much preventing a large piece of the Antarctic ice sheet which has broken away from drifting north into the ocean and heading towards South Africa. The Southern Ocean does not look like it’s going to become warm enough to melt icebergs any time soon. Oh dear. South African variant icebergs may be the ‘tipping point’ which propels the planet into a new and deadly Ice Age. We could call these dangerous icebergs ‘Thunbergs’, after dear Greta, who is forever warning us about tipping points.