Arctic, Antarctic & Glaciers

The Arctic, Antarctica and glaciers.

Perhaps the most compelling evidence suggesting that the global climate is warming is the retreat of mountain glaciers in many parts of the world and also evidence that sea ice extent in the Arctic is also decreasing. These issues are examined by reference to the extensive information available on the Internet. Interestingly, satellite measuring technology is central to knowledge about changes in glaciers, ice sheets, sea ice and snow cover . However, the global warming industry chooses to disbelieve the satellite measurements of the lower atmosphere of 1979 onwards which show a no warming trend globally even though it is a state-of-the-art method relative to the surface temperature record but readily accept satellite technology when it shows sea ice decreases, snow cover decreases and glacier retreats.

The Arctic

The Arctic is comprised of the Arctic Ocean which freezes and thaws, the huge Greenland icecap and the bordering landmasses of Asia and North America. State of the Cryosphere provide a good introduction to the subjects of northern hemisphere snow cover and sea ice while the MMAB Sea Ice Analysis Page and the MMAB Sea Ice Analysis History Page provide current and historical data on Arctic and An tar ctic sea ice extent. How does Arctic sea ice form & decay? , Contribution of melting Arctic ice to sea level change and 20th century changes in Arctic Sea Ice Cover provide more information on the dynamics of the Arctic icecap.

The latter article on sea ice showing stable cover from 1900 to 1950 is at variance with this article (full article available as pdf document here) about temperatures throughout the Arctic which show that the highest temperatures of the twentieth century occurred during the 1930s and 1940s and not towards the end of the century when sea ice cover was apparently least. Table Arctic showing temperature data from a selection of climatological stations around the Arctic rim also shows that the 1930s-40s was generally the warmest period in the twentieth century although there certainly were some very warm years in the 1990s. During late summer 2002, satellite measurements of sea ice extent were at record lows (Articles: Record Loss in Arctic Ice ; New Arctic Studies Point to Warming; Record Melt in Arctic & Greenland) and the latter article mentions the positive phase of the Arctic Oscillation (AO) as a possible explanation which has meant higher temperatures and stormier springs which broke up the ice into smaller pieces facilitating melting. The Arctic Oscillation in winter has been predominantly positive since the late 1980s, while prior to that back to 1950, it was mostly negative. A possible trend to negative AO is apparent and this graph shows that the AO has been negative since mid October 2002 perhaps indicating that a new phase of negative AO has commenced. Positive AO indicates low surface pressure in the Arctic and higher temperatures whereas negative AO indicates high surface pressure and lower temperatures but peak changes in temperature appear to lag peak changes in AO by approximately ten years (see Figure 2 of this article about temperatures throughout the Arctic: SAT is temperature & SLP is surface pressure).

Some scientists dispute that the thinning of the Arctic ice is as dramatic as claimed but is more a redistribution of existing ice ( Arctic's Big Melt Challenged ) while other scientists p oint out that decreasing sea ice cover is not simply a case of melting from above due to higher air temperatures but may also be due to melting from below ( Arctic Ice Melting from Below ). The Top of the World: is the north pole turning to water? discusses factors affecting the recent decrease in Arctic sea ice extent and thickness and in particular identifies the very positive values of the North Atlantic Oscillation (NAO) during winters of the late 1980s to late 1990s which relate to a deep Icelandic low bringing warm Gulf stream water deep into the Arctic which would melt the ice from below. So it is clear that Arctic sea ice extent and thickness are not simply a response to air temperature but are influenced by long term trends of ocean atmospheric circulation like the AO and NAO.

The Top of the World: is the north pole turning to water? also explains why high latitude regions like the Arctic are expected to warm the most during the twenty first century in response to increasing concentrations of atmospheric CO₂. However Arctic temperatures ( Arctic Rim) are not showing a consistent dramatic increase with recent warming being less than the warming of the 1930s and 1940s suggesting that higher atmospheric concentrations of CO₂ are not having the alleged warming effects in the atmosphere which the global warming industry claims.

The Antarctic

The Antarctic Project has a good description of the nature of the Antarctic continent and also discusses iceshelves which are an integral part of the Antarctic environment. The British Antarctic Survey have a statement on Antarctic Climate Change which highlights the Antarctic peninsula as the only region which has experienced clear and equivocal climate change but because climate models do not predict warming in this region of the Antarctic, it is undetermined whether or not higher concentrations of CO₂ has any connection to this warming. The interior of the Antarctic continent is expected to warm the most from higher concentrations of CO₂ but the Antarctic continent as a whole has been cooling (BBC article) since long term records began in the 1950s as shown by the temperature records of Halley and Vostok. It is the melting ice shelves of the Antarctic Peninsula which have made the news in the last decade and this issue is discussed further in the next section on Glaciers.

Glaciers

Three types of glaciers are exist according to the prevailing climate conditions of the environment in which the glacier is found. Glaciation is not simply a response to temperature but is a function of both precipitation which provides the snow for ice accumulation and temperature which must be low enough to permit precipitation in the form of snow and to prevent overall melting of the glacier.
Temperate or mountain glaciers have the largest volume of ice accumulation and loss of the three glacial systems. Precipitation is usually high which leads to high accumulation and summer temperatures are also high resulting in massive melting . The temperate settings see a higher volume of ice move from accumulation to melting than polar or subpolar settings. The glaciers of the E uropean Alps, of Chile, New Zealand, and Alaska are examples of temperate glacial settings.

Subpolar glaciers have a net balance (total volume of ice gained versus lost) between that of the temperate setting and the polar setting. The amount of precipitation is moderate, which leads to a moderate mass of accumulation. There is some surface melting, and also some basal ice melting, but the total amount of melting is less than that of the temperate system. The Antarctic Peninsula, sub-Antarctic Islands, Baffin Island, southern Greenland, Iceland, and Spitsbergen all are examples of subpolar glacial settings.

Polar glaciers Little precipitation occurs in a polar system and there is little loss of ice through melting as even summer temperatures are below 0^oC. Iceberg calving into the sea and evaporation are the only ways to remove ice from a polar glacial setting. The massive ice sheets of Greenland and Antarctica are examples of polar glaciers.

Glacier: Ice is a good introduction to glaciers and Global Glacier Mass Balance is a measure of the global state of the world's mountain and sub-polar glaciers which has been falling continuously since records began in 1960 and the loss of glacier mass has accelerated in the 1990s.

Are mountain glaciers are melting? yes, there is no doubt that mountain glaciers in many parts of the world are melting (BBC articles: the Alps; Italian Alps; Alaska; Bolivia; various; Tanzania) but rapid growth or rapid melting are characteristic of this type of glacier. Several of these articles quote scientists expressing caution about linking these glacier retreats to global warming.

The most studied glaciers in the world are those of the European alps where ice fronts extend below the treeline and have been in full view of settlements for hundreds of years. The best reconstruction of glacial fluctuations are those of the Grosser Aletsch Glacier in Switzerland which goes back 3000 years (Grove, 2001). This reconstruction is based on a great variety of evidence which increases its reliability and shows repeated patterns of glacial advance and retreat throughout the last 3000 years, with the last millennium being characterised by greater overall glacier extent than the earlier two millennia. Within the last millennium, several peaks in glaciation are apparent with one rapid advance starting after 1250 and culminating around 1350, with further peaks of equal size around 1650 and 1850. The Grosser Aletsch in common with other European Glaciers has been retreating more or less continuously since 1850 but current glacial fronts are similar to those of around 1250. So the glacial retreats of recent decades are part of a much longer trend since 1850 of glacial retreat which is itself part of a complex pattern of glacial advance and retreat occurring over centuries.

While European glaciers show comparable glaciation peaks around 1350, 1650 and 1850, north American glaciers show a different pattern of glacier advances and retreats. For example, the Robson Glacier in the Canadian Rockies (Grove, 2001) was advancing into forest from around 1150 and 1350 but advances during the eighteenth and nineteenth centuries were more extensive. In western Spitzbergen, studies of sediment deposition in the mouth of the Isafjorden from meltwater fed by several small mountain glaciers indicate warm conditions in the twelfth and twentieth centuries and lower temperatures interrupted by brief warm intervals in between (Grove, 2001).

There have been reports of glaciers advancing in the last twenty years, in Norway due to higher rainfall and also in New Zealand during the 1990s for a while indicating that it is local climate rather than global climate that dictate whether mountain glaciers advance or retreat. For mountain glaciers in the tropics, this BBC article about a Bolivian glacier suggests that the stronger El Ninos of recent years is a critical factor as they result in both lower precipitation and higher temperatures and this factor may or may not be related to anthropogenic global warming. The dramatic retreat of alpine glaciers during the 1990s is likely to be a response to the highly positive North Atlantic Oscillation (NAO; data) during the winters of this decade. The NAO is the difference in sea level pressure between Iceland and the Azores/Gibraltar region. It is positive while pressure is low near Iceland and high in the Azores when Atlantic low pressure systems tend to pass between Scotland and Iceland on their way to Scandinavia bringing high rainfall to these regions while much of Europe experiences drier and warmer conditions. It is negative while the reverse applies and Atlantic low pressure systems tend to cross the UK or further south across France or Spain bringing wetter and colder conditions to these regions. This graph shows the high winter NAO values of the 1990s and the temperature record for Zurich shows the high temperature of these winters which would have resulted in reduced snowfall in the Alps.
In brief, yes many mountain glaciers around the world are currently retreating but historical reconstructions of some glaciers suggest that these recent retreats are part of a long multi-century cycle of glacial advances/retreats associated with the varying local climate. Attributing them to higher concentrations of CO2 in the global atmosphere is a less reasonable explanation.
Are subpolar glaciers melting? some are and perhaps the most famous ones are those in the Antarctic peninsula which is undergoing a local warming trend (BBC articles: Earth Enters Big Thaw; Antarctic Ice Crumbling Rapidly; Antartctic Lakes show Warming Effects; Antarctic Ice Shelf Collapses.) while the Antarctic continent as a whole cools. In the case of the Antarctic Peninsula, it is climate sensitive ice shelves which are melting rather than the glaciers themselves. Svalbard north of Norway and Iceland also have subpolar glaciers which are retreating.
Are polar glaciers melting? there is no clear consensus on this issue for either Greenland (Greenland Ice Warning; Climate Shift Asserts itself in Greenland.) or Antarctica (Retreat of the West Antarctic Ice Sheet; Antarctic Ice Fringe Melting Faster; West Antarctic Sea Ice not in jeopardy.) While there is evidence that summer melting in Greenland is occurring, some summer melting is normal and Arctic summers during the 1930s and 1940s were warmer (see Table Arctic) . With respect to Antarctica, the continent is cooling overall and it is far too cold anyway for summer melting except on the Antarctic Peninsula.

References

Grove, J. M. 2001: The initiation of the "Little Ice Age" in regions round the North Atlantic. Climatic Change, 48, 53-82.