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Sea Level Changes

4 January 2013

At www.CartRuts.com/pages/prehistoricshoreline.html … there is a nice map of Malta with the shoreline as it was at various times during the Holocene, and showing that in the Ice Age it had been on the end of a peninsular that joined it to the tip of Sicily. This map was produced using recent eustatic sea level prediction methodology of Lambeck (2004) – so it is a model of how it is thought sea levels have gradually risen over time. The fact that such models are presented as facts is of no great importance as the claim is fairly transparent and happens all the time when sea levels around the coasts of NW Europe are discussed. In other words, the maps are guesswork and to say that Malta was an island when humans first entered it is also an educated estimate. Eustatic refers to sea level adjustments that take into account land movements as well as melt waters. In other words, the basis of sea level rise is assumed to involve the melting ice sheets in northern Europe and sea level can only rise, either via thermal expansion of the oceans or by the melting of glaciers somewhere in the world. This hypothesis creates a number of problems – including the fact sea levels were still rising thousands of years after the end of the Ice Age. However, as the author of the site acknowledges, sea levels are thought to have stablised around 5000 years ago (or around 3000BC). In the consensus view sea levels rose at a uniformitarian rate right up to that time and various computations have been made, in different parts of the world, as to when certain parts of the continental shelves may have flooded, including the North Sea Basin and Irish Sea. While the latter is believed to have formerly been a glacier and by depression caused the Irish Sea to drown somewhat earlier than the English Channel or North Sea basin, we may note that all is not necessarily as it is presented in the consensus models. Paul Dunbavin, in Under Ancient Skies: ancient astronomy and terrestrial catastrophism (available from the SIS Book Service) and in his earlier book on the Earth's rotation, argued that there was a small shift in the axis of rotation at around 3000BC, caused by unknown forces but which involved a readjustment of the equatorial bulge and worldwide sea levels. It occurred in an instant, without any surge or massive upheaval, and no hint of a tsunami wave. The tide came in – and continued to come in until the new global ocean level was reached. In other prts of the world, such as China, the tide failed to come in as far as it had – and new land was available for humans to exploit. We may note that there was an even bigger adjustment of the geoid around 6000BC. See for example Stephen Oppenheimer, Eden in the East: the Drowned Landscape of SE Asia (available for a snip at Amazon). As Lonnie Thompson has demonstrated in various papers and articles, glacial advance was a distinct feature of 3000BC. This was also the time when the body of the Ice Man was embodied in a glacier in the Alps (and remained encased in ice right up to the modern day when the glacier retreated far enough to reveal his remains). This may have something to do with altitude – the Alps rising in relation to sea level, and the same thing in the Andes as noted by Thompson (plants frozen in situ were revealed by a melting mountain glacier). That  appears to imply modern warming is something out of the ordinary – but it also means the period prior to 3000BC was also very warm. There was in fact a recognised phase of global cooling around 6000BC, generally thought to have lasted a couple of centuries, and variously global cooling is associated with the era around 3000BC, driving horse mounted barbarians from the Russian steppe into the Near East where their remains were found in tombs at Ur, having established a ruling elite.  These barbarians were migrants with origins associated with the kurgans on the steppes, and the tombs at Ur reflect this association. The period between 3000 and 6000BC is generally defined as the Mid Holocene Warm Period (in the US) and the Atlantic climate period (in the UK). Global temperatures at this time were higher than today, it is thought, and even show up in AGW climate science graphs – when they dare reach back so far. It is generally recognised that trees grew further north than they do nowadays and at higher altitudes too. Northern Britain, in the 4th millennium, had a climate somewhat like southern England nowadays – which is why it was colonised by the early farmers. In other words, if there was any vestige of a northern ice sheet, or glaciers loitering on the flanks of mountains, they would have disappeared during the Mid Holocene Warm Period. In Paul Dunbavin's opinion this was all to do with the axis of rotation, and it may be no accident that the warm period squats between two steep rises in sea levels. Therefore the situation may be quite different than imagined by Lambeck, and others. We may also note the idea of gradual sea level rise was a ploy to airbrush out of existence the idea of movement at the Poles or axis of rotation. It was also a useful way of explaining how the huge northern ice sheet had disappeared – the ice had become oceanic water. Even now CAGW advocates in the climate science fraternity regularly regurgitate stories of melting ice at the Poles leading to massive sea level rise. As far as the Arctic Ocean is concerned most of the ice is in the water and below the water and will not cause much of a rise and the same is true of the West Antartic peninsular to a certain degree. The ice sheets on Greenland and continental Antarctica differ in that they are above sea level – but there is little evidence of them melting. They were alive and kicking during the Mid Holocene Warm Period and therefore it will take a bigger rise in temperature than we have experienced to make any difference to them in the modern world.

By far the major rise in sea levels occurred at the end of the Ice Age, after 15,000 years ago. The rise was spectacular and could be explained by Pole movement, as envisaged by Peter Warlow in his talk at the last SIS Cambridge Conference (available in the Proceedings from the SIS Book Service). It would explain why there is no evidence of glaciation in Siberia and northern China during the Late Glacial Maximum, supported by the mammal assemblage found in the caves at Khoukoudian. It might also explain why Tigers still live in Siberia, adapting to the cold, and why Rhinocerus were part of the fauna of China until fairly recent times (and other exotic species). Clearly, from a uniformitarian perspective it is necessary to have a huge northern hemisphere ice sheet rather than a repositioned ice sheet, and a difficult consensus theory in which to make a dent. Sea level rise is invariably cited in support of the existence of such an ice sheet – even the sharp spike around 6000BC. Smoothing is achieved by modelling such as Lambeck but old papers insist the rise was rapid at that time – see the notes and bibliography supplied by Oppenheimer and Dunbavin. Where did all that surplus water come from we might ask, thousands of years after the end of the Ice Age. If it was melting ice where did it hang around during the Mid Holocene Warm Period?  The fallacy of attributing rising sea levels to declining glaciation is compromised as there was a cooling period of around 200 years following the event – when glaciers would have been growing. Meanwhile, the continental shelf around NW Europe was drowned but the South American coastline was raised. Lake Titicaca was transformed from a coastal lagoon to a mountain lake high in the Andes, thrust upwards. Tectonic forces may have been involved but mountain building in the Andes is generally dated much earlier than this – millions of years in the past rather than a few thousands. A few years ago an earthquake in Chile managed to move South America skew whiff by several feet, and the earthquake that gave rise to the Boxing Day tsunami in the Indian Ocean is said to have moved the Poles by a few inches. Hence, we are probably looking at something more significant than tectonic activity – although that could have been involved as a consequence.

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