Australia: The Land Where Time Began
Climate Change Science – Melting Ice
In nature most ice is in the form of glaciers, ice sheets, sea ice, permafrost, and in clathrates on the ocean floor. Other forms it is present in are on lakes and streams in the colder times of year in mid-latitudes and at high elevations, as icebergs, and as ice shelves and ice caps. It been shown that most of this ice is melting at various rates, some more rapidly than others, though in some locations local conditions can lead to the ice expanding at different times of the year, but the trend of the ice of the Earth is apparently to continue diminishing.
Debate has taken place over the glaciers in the Himalaya Mountains since an error was discovered in the IPCC AR4 report in 2007. According to the report the glaciers of the Himalayas were melting at a more rapid rate than was actually happening. The error was corrected but some are still criticising the 2007 report. The lower reaches of the Himalayan glaciers are receding, though it seems some may actually be gaining ice at higher elevations, at elevations that will take a lot more warming before they retreat. Temperatures at those elevations are lower and at those elevations most of the precipitation is in the form of snow.
IPCC AR4 2007 report was comprised of 4 major sections with many supplementary reports. These sections are:
Contribution to Working Group I (WGI): Climate Change 2007: The Physical Science Basis.
Contribution to Working Group II (WGII): Climate Change 2007: Impacts, Adaptation and Vulnerability.
Contribution to Working Group III (WGIII): Climate Change 2007: Mitigation of Climate Change.
Contribution of Working Group I, II, and III: The Synthesis Report (SYR).
The IPCC AR4 2007 report, Climate Change 2007: The Physical Science Basis, assessed current scientific knowledge of “the natural and human drivers of climate change” as well as changes in the climate that had been observed. It looked at the ability of science to attribute changes to different causes, and also made projections of future climate change.
There were 676 authors involved in the production of the Physical Science Basis, of which 152 were lead authors, 26 review editors, and 498 contributing authors, from 40 countries, and then reviewed by 625 expert reviewers. The cited publications amounted to 6,000 peer-reviewed publications. Farmer & Cook say it is amazing that only 2 mistakes were found in such a huge body of work.
The summary was reviewed line by line by representatives of 113 governments during the 10th session of the WGI, in January to February 2007.
There has been a steady decline in the extent of Arctic ice while the sea ice in Antarctica has apparently been expanding. This does not necessarily mean that the Antarctic is cooling, as sea ice is frozen water and the extent of sea ice may be deceptive. It is possible to have global warming and expanding sea ice occurring at the same time if the volume of ice throughout the globe is decreasing. The extent is not necessarily related to volume, as new ice may be forming at the surface of the ocean as old ice is reducing in volume, as is happening in the Arctic and the Antarctic.
A fairly recent study gives comparisons of the thickness of sea ice in the Arctic over time. In this study, sea ice thickness records from submarines and ICESat (NASA’s Ice, Cloud and Elevation satellite) observations from 1958-2008 (ICESat’s laser altimeter). When 42 years of submarine records, from 1958-2000, and 5 years of ICESat records, from 2003-2008, it was determined that the mean thickness of Arctic sea ice had decreased from 3.64 m in 1980 to 1.89 m in 2008, a reduction of 1.75 m.
It has been shown by a study in February 2012 that the oldest and thickest ice in the Arctic is melting more rapidly than younger, thinner ice at the edges of the ice cap. The vulnerability of the sea ice in the Arctic Ocean to further decline is increased by the rapidity of the melting of the older ice.
The thickest ice, the multi-year ice, remains through 2 – more summers, but the young seasonal ice forms each winter then melts in summer just a fast as it formed. A 3rd category, “perennial” ice cover, is all ice cover that has survived for at least 1 summer. All multi-year ice is perennial, but not all perennial ice is multi-year ice.
|Author: M.H.Monroe Email: firstname.lastname@example.org Sources & Further reading|