Archive for December, 2013

Myths of the Giant Oarfish

Wednesday, December 11th, 2013

Giant Oarfish (Regalecus glesne) have been in the news again recently. Two washed up dead on the coast of California in October, one at Santa Catalina, the other near San Diego. They are lousy swimmers, and probably got caught in coastal currents they couldn’t fight successfully.

A dead giant oarfish is still a remarkable thing. These two were 4-5 meters long, but they can grow to as long as 11-12 meters No other bony fish species grows longer.

About 20 men holding up one giant oarfish (wikipedia.com)

About 20 men holding up one giant oarfish (wikipedia.com)

They are also rarely seen by humans, so every corpse is a new source of amazement. Normally the fish are pelagic, living well off shore, probably usually in deep water – their large eyes suggests adaptation to the deep dim world a few hundred meters below the surface.

And there the mystery of this fish remains. Cruising through the science articles that mention them usually just describe another dead animal that has washed up somewhere new.

The little information we have suggests they spend their time hovering vertically in the water, propelled slowly by a long and undulating dorsal fin while the rest of the body doesn’t move. You really need to see this to believe it: a robot camera captured one a couple of years ago.

Dead medium sized oarfish lying beside living child. The long dorsal fin is typically red (strangesounds.org)

Dead medium sized oarfish lying beside living child. The long dorsal fin is typically red (strangesounds.org)

We know they they are toothless, lack scales, and have small mouths. As they hover vertically, they are probably feeding, sucking in plankton and euphausids or krill and straining them from the water they push through their gill-rakers. Perhaps they somehow eat small fish. They certainly can’t chase down prey, and they grow too large to be prey for most other fish besides sharks. Somehow they don’t turn up in fishermen’s nets very often, and in fact seem able to avoid the nets.

A living oarfish, rarely seen (ferrebeekeeper.wordpress.com)

A living oarfish, rarely seen (ferrebeekeeper.wordpress.com)

What else? Their meat tastes mushy, gelatinous, so they are safe from human predation. There are perhaps 4 different oarfish species of different sizes around the world. They have been observed, usually dead, most often in warm-temperate waters. An old quote: “A dead oarfish is about as tough as wet cardboard.”

A very small juvenile oarfish, a very rare find. Captive,offered for sale, it soon died (reefbuilders.com).

A very small juvenile oarfish, a very rare find. Captive, offered for sale, it soon died (reefbuilders.com).

And the myths? Perhaps they change gender as they grow larger (many fish do). Perhaps they shed the ends of their tails the way some lizards do (maybe the ends just fall off more quickly from dead animals). Perhaps they are the source of mariners’ tales of huge sea serpents (those seen at the surface are usually sick or dying, and could perhaps have inspired the mariners). Perhaps they are especially sensitive to Earth tremors – for example, before the 2011 tsunami in Japan, 20 beached themselves and died (who knows?).

Probably none of these are true, but we really lack the facts that dispel most myths.

What we have here is a most bizarre fish, rarely observed alive and healthy, of no commercial value to us. It probably isn’t endangered, though it certainly is not abundant. It shares this planet with us, mostly out of our view, which is the safest place for it to be. It is a reminder that life on Earth is incredibly diverse, and that not only do we not know everything about everything, but that in fact perhaps we don’t need to know.

It just is.

Eemian Evidence

Sunday, December 8th, 2013

So what do we really know?

We’re deep in an Ice Age, the third that has occurred in the past half billion years. In between Ice Ages, the Earth has been very warm, in its ‘hot-house’ phase, with high sea levels and free of glaciers and ice caps.

The Ice Ages that preceded ours occurred 290 and 440 million years ago. Note that the time scale is more compressed on the left(acer-acre.ca)

The Ice Ages that preceded ours occurred 290 and 440 million years ago. Note that the time scale is more compressed on the left(acer-acre.ca)

Our Ice Age began 2.6 million years ago, caused at least in part by the drift of Antarctica to cover the southern polar region, and the northern continents closing off much of the Arctic Ocean. Without cold polar water easily mixing with warm tropical water, polar ice caps and glaciers formed and grew, and the global average temperature dropped from about 22 degrees C to about 12 degrees C.

plate_history_lge classroomatsea.net

The continents drift endlessly, slowly, on 12 plates driven by convection currents in the magma below the Earth’s crust (classroomatsea.net)

During our Ice Age glacial and interglacial periods have cycled regularly. We’re in an interglacial period now, but even the interglacial periods are cool – the ice caps just retreat, they don’t completely melt, for cold polar water is still trapped in the Arctic and around Antarctica.

In our current Ice Age, glacial and interglacial periods cycle with remarkable regularity (atala.fr)

In our current Ice Age, glacial and interglacial periods cycle with remarkable regularity (atala.fr)

Our interglacial period, which we’ve named the Holocene Interglacial, started about 12,000 years ago. Probably not merely coincidentally, while we as a species have evolved over the whole time of this Ice Age, our explosion into whatever it is we are now began with the onset of the Holocene Interglacial.

Antarctic temperatures and atmospheric CO2 and Methane levels over the past four cylces of glacial and interglacial periods (eoearth.org)

Antarctic temperatures and atmospheric CO2 and Methane levels over the past four cylces of glacial and interglacial periods (eoearth.org)

We have also learned much from the analysis the last interglacial, the Eemian Interglacial, which began 130,000 years ago and lasted for about 20 thousand years. An ice core drilled into the northern Greenland ice sheet reached down to bedrock through 2.5km of ice, and back 250,000 years. The drilling took three years, the analysis another year, and the results were published in Nature last January.

The NEEM ice core was taken from the northeern part of the ice sheet where the deepest ice is 250,000 years old (neem.dk)

The NEEM ice core was taken from the northeern part of the ice sheet where the deepest ice is 250,000 years old (neem.dk)

In the Eemian Interglacial, global average temperatures were about 4 degrees C warmer than our current global average; CO2 levels rose to about 320 parts per million, sea levels rose about 6-8 meters higher than present, and the Greenland ice sheet melted from about 200m higher than present to about 130 lower than it is now. Since the Greenland ice sheet didn’t all melt during the Eemian Interglacial, the rest of the sea level increase must have come from the melting of the West Antarctic ice sheet.

Knowing all this, what can we truly predict about our future? We have clear models from the recent and from the more distant past of what the possible outcomes actually would be.

With atmospheric CO2 levels as high as they are at present, 393 ppm as of October, we can expect the global average temperature to become at least a few degrees warmer, and sea levels to rise at least a few more meters.

Average global temperature tracks CO2 levels over the past 400,000 years. Our Holocene Interglacial is on the extreme right, and our CO2 levels are striking (icecore_records-sympatico.ca)

Average global temperature tracks CO2 levels over the past 400,000 years. Our Holocene Interglacial is on the extreme right, and our CO2 levels are striking (icecore_records-sympatico.ca)

If CO2 levels continue to rise, as they are likely to do, we may force the Earth prematurely out of this Ice Age and back to its hothouse phase, over-riding the impact of continental drift in keeping the poles cold.

Obviously this is an ever changing planet, whether or not we are here to ride it out, and any sense we have that it is stable, benign or in any kind of equilibrium is shear delusion on our part.

But we have increased the pace of change, and this is going to be quite a trip. There are an awful lot of us on the planet, and if the changes happen as quickly as all the graphs from the past indicate they will, the human cost of the upheaval is going to be huge.

Of course we can adapt, but we need more time to do so without excessive misery.
We still do have the potential to limit both the extent and the pace of global warming.

Celebrating the last piece of ice core, extracted from 2.5 km below the surface of the Greenland ice sheet (neem.dk)

Celebrating the last piece of ice core, extracted from 2.5 km below the surface of the Greenland ice sheet (neem.dk)