At http://sciencenordic.com/greenland-icebergs-may-have-triggered-younger-d… … courtesy of https://cosmictusk.com/younger_dryas_ice_bergs_greenland_hiawatha_comet/ … Greenland ice bergs may have triggered the Younger Dryas event is the title of what is a 2013 post. This is a variation on the old theory that Canadian melt water flow into the North Atlantic and caused the cooling period (which lasted a 1000 years, or longer). As such it is a peculiarity as climate blips usually last a fraction of that time. It may suggest the Younger Dryas event has some odd properties – and indeed it has as it was not universally cold and glacial but appears to have varied in effect over the longer time span. This has always been a problematical theory as facts on the ground have never provided the necessary support. For example, a huge melt water flow did not exit via the St Laurence sea way – the most obvious route as such a flow of water would have scoured out tell tale marks in the geology. It was subsequently suggested that meltwaters may have flowed through the McKenzie river watershed and out into the Arctic Ocean, by-passing the St Lawrence outflow. Now we have the idea of melting glaciers in Freenland as responsible – and of course the evidence must pre-date the Younger Dryas in order to get room to manoevre (a period in which the gradual ice berg movement built up enough momentum to actually cause a change in the Atlantic water circulation system – i.e. stoppping the circulation in full flow and forcing it to overturn south of where it overturns in the modern world. It sounds a good idea but is it? Can a thousand year cooling have been caused by ice bergs calving from Greenland?
The second link (to Cosmic Tusk) poses the possibility the Hiawatha crater in NW Greenland may have been a catalyst to create a situation in which lots of ice calved from Greenland as required for the theory to have much ballast. A younger dyras boundary date has not yet been ruled out but we should also bear in mind that other events are thought to involve airburst or multiple airbursts as the Earth encountered Taurid Stream cometary material, left behind by the passage of a comet, so why should the Younger Dryas be any different. Enough heat from blast waves to melt ice on Greenland could have derived not from an impact event but simply from meteors exploding in the lower atmosphere. Whether enough ice could have actually caused the Atlantic system to cut short south of Greenland is a moot point.
The Great Lakes, we might imagine, are the greater residue of the glacial melt waters, preserved at the bottom end of the Late Glacial ice sheet. The myriad number of lakes and ponds and streams and rivers in Canada and the north eastern states of the US may also have a similar origin in a melting ice sheet – but Greenland still has an ice sheet. It does not of course completely cover Greenland – but a goodly proportion. The research in the first link is derived from sea bed cores off the coast of Greenland and refer to sediments which they say date from just prior to the Younger Dryas event. Some may like to take issue with the specific dating methodology used in the study but suffice to note that for the research to have any relevance it was necessary to date the Greenland icebergs prior to the Younger Dyras. What they found is that most ice flow came from the American continent and somewhat later, appears to have originated from Greenland. Sand and gravel, and a mud layer were involved. Dropstones from icebergs are the suggested evidence – although heavy outflow of water could equally have caused material larger than gravels to become lodged on the oceanic sea floor (or that part of it known as the Labrador Sea). Most of the sediment with an origin in Canada date from 16,000 to 17,000 years ago (the end of the Late Glacial Period defined as the Oldest Dryas event). The fact the end of the Late Glacial Maximum (ice sheet extent) coincided with a cooling period even greater in time than 1000 years, and possibly as long as 3000 years, tells us something extraordinary was going on – something we can only suspect rather than put our fingers squarely on a cause. Presumably, the end of the deposit of sediment with an origin in the Canadian mainland suggests that most of the ice sheet had melted within a couple of thousand years – the warming period known as the Bolling-Alleroed in Erope (divided by the Older Dryas event, a period of a few hundred years only). Might this explain the shift to sediments with an origin in Greenland (which still has an ice sheet) which may have been inspired by the cooling of the Older Dryas creating an extended ice sheet growth episode (which shrank back down again after the warming kicked back in). I would assume that if the Hiawatha crater played a role it would coincide with the Younger Dryas boundary rather than precede it (but the dating methodology is of course a means to an end). We have a situation, one might say, that requires down play rather than bigging up. The shift to Greenland sediment could have involved simple natural ice melt over a longish period as Greenland once again settled down into the global warm period, rather than exaggerating the evidence to provide a hypothetical link to the Hiawatha crater (which may be much older than the 13,000 years ago Younger Dryas event). What actually caused the Oldest, the Older, and the Younger Dryas events (as well as the onset of the Late Glacial Maximum) is a more pressing problem that could be defined, theoretically, as periodic encounters with streams of cometary material orbiting within the Taurid complex (as originally theorised by Clube, Napier, Asher, Steele, Bailey and others back in the 1990s). Such events would perhaps have had electro-magnetic effects as it seems likely such streams of material were electrically charged (as discovered in recent comet missions). It's all to play for and it comes thanks to recent space missions (and arrays of space telescopes). New discoveries are being written about virtually every week. If perchance the Hiawatha crater is of Younger Dryas boundary date and then that would be firm evidence of a climate changing cosmic slap. Unfortunately, we would have to theorise similar impacts occurred at the Oldest Dryas event, and prior to the Late Glacial Maxmum – and possibly even prior to that. It will be interesting to see what date is finally put on the Hiawatha crater (if indeed it is a crater). Catastrophism is such fun – and with all kinds of possibilities (and extinction events from big to little) as our Earth orbits around the Sun, maintaining a path through a solar system populated by comets and streams of stones and gases as well as asteroids and meteors and objects as small as dust particles, and on top of that space and plasma (everywhere). We have a stream of plasma striking the ionosphere of the Earth this very day – with an origin in a coronal hole on the visible surface of the Sun (see http://spaceweather.com).