Reading a little of the press this weekend on the subject of Lake Agassi, the giant melt water lake that developed as the ice age melted away got me thinking. Just how much ice was sitting on land in the first place? We know that it was enough to raise the sea level by a good 100 meters over three millenia.
Knowing the area of the world ocean to be around 361 million square kilometers (wikipedia) we quickly convert this to a total volume of around 3,000 to 4,0000 cubic kilometers of ice. Surprisingly, this actually matches our expectations and we would have accepted a lot more. Of course, crustal depression may have accommodated a lot more as a rising crust theoretically produces more volume for the ocean.
Surprisingly, the annual melt rate therefore averages around a cubic kilometer per year. which is quite moderate. It looks like a lot but it was actually rather slow, melting at a stately few net inches per year rather like our current glaciers.
All the melt water did end up in the Atlantic and this created a annual pulse of fresh surface water into the ocean that must have mixed with and impacted the dynamics of the oceanic current system and its related weather. We can also be sure that this annual pulse was relieved by the escape of water into the South Atlantic and around the gap between Antarctica and South America, possible in the form of warm equatorial waters. We will let the speculators go crazy over that possibility.
On average, however, the sea level rose about one meter every generation or so for a period of three thousand years. More importantly, it did not go catastrophically faster at any time with perhaps the sudden release of Lake Agassi. This meant that populations had plenty of time to plan their response.
It certainly explains why a rising sea mythology is so deeply embedded. This was continuously observable to anyone near the sea. One other effect that is not so obvious is that the inter coastal region was always migrating and the related biosphere was always playing catch up. This surely had an impact on the productivity of these traditional sources of food that we do not yet appreciate.
So we can dismiss the idea of a sudden deluge that swept away countries although countries were overwhelmed such as the Indonesian Plain and the North Sea Plain in particular. Both were important sites of human habitation. And do not forget that what was lost globally was the continental shelf fairly early on. The creation of that plain may be our best proof of the duration of the Northern Ice Age.
I think that the current crustal configuration is incredibly stable, because it will be impossible for a Northern ice age to get going. No other crustal configuration could have served us as well, so long as the Atlantic is closed at the Equator and the Northern portion of the Equatorial Waters is forced into the Arctic. It is also obvious that a Northern Ice Cap is the norm throughout most of Global history, even if we have not found all the records. The only way that it is avoided is if the pole is open ocean as we have today to some degree and a source of warm water is available.
It is also interesting that the crust in the Northern Hemisphere appears to be somewhat in dynamic balance balance around the pole as is the continent of Antarctica around the South Pole. It may mean nothing, except to give encouragement to those supporting the idea that the build up of the northern ice cap was sufficient to trigger crustal slippage that ultimately stabilized into this very advantageous position. Maybe human good luck was inevitable.
On the other hand, those coastal plains were pretty extensive and also pretty livable unlike the arid hinterlands and related highlands. They could well have supported large human populations as equivalent lands do today. We simply do not know and perhaps can never know.
The point that we can make is that for the past ten thousand years and perhaps for the next million years, the global climate will no longer be kicked around by a growing Northern Ice Cap whose impact reaches deep into the temperate zone. We may even see the Greenland Ice Cap partially disappear while parts of the Antarctic cap should actually grow by a like amount.
This gift of Holocene climate stability should go on giving for a long time after we come to our senses and stop using the atmosphere and the ocean as a dumping tip.
Knowing the area of the world ocean to be around 361 million square kilometers (wikipedia) we quickly convert this to a total volume of around 3,000 to 4,0000 cubic kilometers of ice. Surprisingly, this actually matches our expectations and we would have accepted a lot more. Of course, crustal depression may have accommodated a lot more as a rising crust theoretically produces more volume for the ocean.
Surprisingly, the annual melt rate therefore averages around a cubic kilometer per year. which is quite moderate. It looks like a lot but it was actually rather slow, melting at a stately few net inches per year rather like our current glaciers.
All the melt water did end up in the Atlantic and this created a annual pulse of fresh surface water into the ocean that must have mixed with and impacted the dynamics of the oceanic current system and its related weather. We can also be sure that this annual pulse was relieved by the escape of water into the South Atlantic and around the gap between Antarctica and South America, possible in the form of warm equatorial waters. We will let the speculators go crazy over that possibility.
On average, however, the sea level rose about one meter every generation or so for a period of three thousand years. More importantly, it did not go catastrophically faster at any time with perhaps the sudden release of Lake Agassi. This meant that populations had plenty of time to plan their response.
It certainly explains why a rising sea mythology is so deeply embedded. This was continuously observable to anyone near the sea. One other effect that is not so obvious is that the inter coastal region was always migrating and the related biosphere was always playing catch up. This surely had an impact on the productivity of these traditional sources of food that we do not yet appreciate.
So we can dismiss the idea of a sudden deluge that swept away countries although countries were overwhelmed such as the Indonesian Plain and the North Sea Plain in particular. Both were important sites of human habitation. And do not forget that what was lost globally was the continental shelf fairly early on. The creation of that plain may be our best proof of the duration of the Northern Ice Age.
I think that the current crustal configuration is incredibly stable, because it will be impossible for a Northern ice age to get going. No other crustal configuration could have served us as well, so long as the Atlantic is closed at the Equator and the Northern portion of the Equatorial Waters is forced into the Arctic. It is also obvious that a Northern Ice Cap is the norm throughout most of Global history, even if we have not found all the records. The only way that it is avoided is if the pole is open ocean as we have today to some degree and a source of warm water is available.
It is also interesting that the crust in the Northern Hemisphere appears to be somewhat in dynamic balance balance around the pole as is the continent of Antarctica around the South Pole. It may mean nothing, except to give encouragement to those supporting the idea that the build up of the northern ice cap was sufficient to trigger crustal slippage that ultimately stabilized into this very advantageous position. Maybe human good luck was inevitable.
On the other hand, those coastal plains were pretty extensive and also pretty livable unlike the arid hinterlands and related highlands. They could well have supported large human populations as equivalent lands do today. We simply do not know and perhaps can never know.
The point that we can make is that for the past ten thousand years and perhaps for the next million years, the global climate will no longer be kicked around by a growing Northern Ice Cap whose impact reaches deep into the temperate zone. We may even see the Greenland Ice Cap partially disappear while parts of the Antarctic cap should actually grow by a like amount.
This gift of Holocene climate stability should go on giving for a long time after we come to our senses and stop using the atmosphere and the ocean as a dumping tip.
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