Changing levels of the sea

18 Jul 2011

At is a guest post by Tony Brown at Judith Curry's web site Climate Etc - Brown has his own web site at Basically, there were big changes in sea level at the end of the Ice Age - and a further surge around 8000 years ago. Since that period the sea level has been surprisingly uniform - just a few jumps and plunges at significant points in time (3000BC for example, or towards the end of the 3rd millennium BC). The huge jump between 18,000 and 8000 years ago is represented in a graph as a line going upwards as if it proceeded sequentially rather than in fits and starts. Brown does not question the consensus view that sea levels rose in this period as a result of the melting of a huge ice sheet in the north - in spite of the fact that it took an extraordinarily long time to melt and the fact that forests were growing in regions of that former ice sheet within a couple of thousand years. In spite of overlooking this more obvious anomaly Brown clearly is not after rocking the boat in a big way - yet he still manages to upset the AGW alarmists as the comments show. This is because of what he says happened after 8000 years ago, when sea level was fairly constant, simply by quoting such run of the mill books as Brian Fagan's, The Little Ice Age, and archaeological studies of the North Sea basin, the area known as Dogger Land (Bryony Coles). The North Sea basin, as far north as Norway was dry land during the Late Glacial Maximum - and an indeterminate period thereafter. In other words, Norway, Denmark, North Germany and the Netherlands, as well as the Orkneys and possibly the Shetlands, were all part of a continental shelf system that was above the sea - but you don't get a proper sense of this in this post. Brown concentrates on recycling material that has been published by others, and using it to show that sea levels have gone up and down over the last 5000 years or so when anthropogenic global warming could not have been happening. In spite of this the post is interesting as it has a bit about Mounts Bay and Cornwall in general, the isles of Scilly, the Fens, the region opposite East Anglia on the other side of the North Sea, and the isle of Wight. The latter has of course been covered by Steve Mitchell in an SIS article - here referring to Bouldner cliff on the coast of the Solent. Apparently, the BBC Time Team did a programme about Bouldner, where a Mesolithic settlement and boat yard was found at the bottom of the cliff, beneath a huge deposit of peat and other sediments, and they claimed that it was drowned by gradual sea level rise, at the rate of 2cm a year - which is ten times the rate of sea level rise that has taken place subsequently. Obviously, the numbers are being used to hide an anomaly - very rapid sea level change around 8000 years ago. On another occasion he appears to repeat information Steve Mitchell has written about - a rise in sea level in the North Sea between AD350 and 550, the Late Roman period. An extra two feet of water created problems not only in eastern England but elsewhere, in the Netherlands for example, North  Germany and Denmark. This fact underlies the migrations of peoples at this time, such as the Jutes, Angles and Saxons. At the same time the isle of Thanet was affected, he says, and a Roman road in South Yorkshire was buried under sediments - in the middle of the third century AD. There were four transgressions in the Thames valley during the Holocene it would seem and the fourth of them occurred in the late Roman era. Settlements in lowland regions were abandoned and recommence in the 7th and 8th centuries AD - in areas previously favoured by the Romans. A similar situation has been found in the Mediterranean, he says as he widens the area of research - and has some interesting details from what is now Israel.