Antarctic Iceberg Could Threaten Sea Life In the Region

For many fish in the Antarctic regions it might seem like the “sky” is falling, as a piece of the Antarctic shelf the size of the state of Rhode Island has broken away, and is floating on its own. The areas under the “floating state” are possibly in danger of the wildlife located underneath being oxygen starved, as the area no longer has the ability to be oxygenated at the air-sea interface.

[BBC]

A vast iceberg that broke off eastern Antarctic earlier this month could disrupt marine life in the region, scientists have warned.

They say the iceberg, which is 78km long and up to 39km wide, could have consequences for the area’s colonies of emperor penguins.

The emblematic birds may be forced to travel further afield to find food.

The iceberg calved from the Mertz Glacier Tongue after it was hit by another huge iceberg, called B9B.

“It is a very active area for algae growth, especially in springtime,” explained Dr Neal Young from the Australia-based Antarctic Climate and Ecosystems Co-operative Research Centre.

Iceberg ‘size of Luxembourg’ threat

“There are emperor penguin colonies about 200-300km away to the west. They come to this area to feed, and seals in the area also come to get access to the open water,” he told BBC News.

He suggested that a change in the availability of open water could affect the rate of food production, which would have an impact on the amount of wildlife it could sustain.

“If the area gets choked up (with ice), then they would have to go elsewhere and look for food.”

Changing landscape

The calving of the iceberg, which has an estimated mass of 700-800bn tonnes, has changed the shape of the local geography, Dr Young explained.

“We have got two massive icebergs that – end to end – create a fence of about 180km.

“So the area’s geography has changed from a situation where we effectively had a box in which two sides were open ocean,” he told BBC News.

“Now we have a fence across one side of the box.”

Before the formation of the iceberg, the Mertz Peninsula provided the right conditions for a polynia – an expanse of open water surrounded by sea-ice – to exist.

“Winds blow off the coast and clear anything in that region, including sea ice, exposing open water,” Dr Young explained.

He added that as well as providing a feeding site for the region’s wildlife, the polynia also was a key production site of “bottom water”; very cold, dense water that sinks to the ocean floor.

“Sea ice is relatively fresh compared to sea water, so the more sea ice you have (in the surrounding area), the more salt that is left in the remaining open water.”

The rise in the concentration of salt increases the water’s density, causing it to sink to the bottom of the ocean.

“This area around the Antarctic coastline, of which the Mertz Peninsula is one part, produces about one quarter of the Antarctic’s bottom water, but the Mertz polynia is a major contributor,” Dr Young said.

He added that the new iceberg had shortened the length of the Mertz Glacier Tongue, which could result in pack ice entering the area and disrupting the polynia.

“That means that the bottom water production rate… will decrease.

“The bottom water spills over the continental shelf, flows down the continental slope into the deep ocean.”

This process helps drive the “conveyor belt” of currents in the Southern, Pacific and Atlantic Oceans.

Any disruption to the net flow of bottom water could result in a weakening in the deep ocean circulation system, which plays a key role in the global climate system.

‘Natural laboratory’

However, the researchers say the changes to the region triggered by the formation of the new iceberg will not shut down the circulation system or affect the world’s climate.

“Large icebergs always attract a lot of attention due to their scale,” observed Dr Michael Meredith from the British Antarctic Survey, who was not involved in the research.

“Bottom water is indeed an important part of the global ocean overturning circulation and hence climate,” he told BBC News.

“There are also a number of other locations of bottom water formation, however. So, it’s unlikely that a large-scale sustained change of the order of magnitude required for a global climate impact will happen from this one event.

“The more important thing, I think, is that this event has been closely and carefully monitored by scientists, who will now look at the processes whereby such calvings can impact on the ocean and the ecosystem – and studying this natural laboratory will add to our knowledge of how the Antarctic system works.”

The fact that this sort of thing – a breaking away of a huge chunk of ice that has been in place for hundreds of years – has not been observed in modern times is more evidence that the problem of pollution of all kinds is making changes like never before in Earth’s history.

Whether you call it global warming, a reference to the overall increase in average temperature worldwide, or simply climate change, noting that some places are experiencing temperatures lower than ever before at the same point in the year, the change is there, and not slowing anywhere observed.

Personally, I find that much of the problem with the message for the unbelievers is the method of delivery. Using the Henny Penny –  “sky is falling”  method will only anger those who can see that no change is happening in a manner that we could call quick. The problem is one of creep, along the lines of the frog placed in the pot of warm water, never noticing the fact he is being cooked by degrees, as the heat slowly rises. It is this creep that we must observe, and work to stop, so that the predictions of land mass loss, for example, due to increased sea levels does not take away more land mass than the world as a whole is prepared to deal with.

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Large icebergs always attract a lot of attention due to their scale

Dr Mike Meredith,
British Antarctic Survey




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