Sunday, June 25, 2006

Sea levels ,Antarctic ice and the natural balance.

One of the main scary tales used by the proponents of AGW is the raising of sealevels and coastal and regional flooding.Indeed this was a central plank of the NZ climate change conference earlier this year.Mostly model extrapolation was used that even disagrees with the IPCC estimated levels of 10-15 cm per century.

This week with the Al Gore science fiction movie getting discussion in the world press there are a number of inconvenient scientific papers and observations that suggest that hollywood and fact are some distance from the intellectual capacity of the proponents and MSM.

Arctic sea level has been falling by a little over 2mm a year - a movement that sets the region against the global trend of rising waters. A Dutch-UK team made the discovery after analysing radar altimetry data gathered by Europe's ERS-2 satellite.
It is well known that the world's oceans do not share a uniform height; but even so, the scientists are somewhat puzzled by their results.

Global sea level is expected to keep on climbing as the Earth's climate warms.

Andrey Proshutinsky from the Woods Hole Oceanographic Institution (WHOI), US, commented that it was vitally important to consider sea level using a range of scientific instruments - and to place significance only on long-term data sets.
His analysis of Russian tide gauges has also hinted at a sea-level fall during the 1990s. He said this seemed to fit with the phases of the so-called Arctic Oscillation, a seesaw pattern of change in atmospheric pressure over the polar region and mid latitudes.


"This is something like decadal variability. Sea level goes up and down, up and down - but in general, it rises," the principal investigator from WHOI's Investigation of Sea Level Rise in the Arctic project explained.

So we see both melting ice sheets and falling sealevels which is against the IPCC models we also see rising levels of GROWTH in the Antarctic ice sheets.Grace was used as evidence by the British antarctic survey at the NZ climate conference of change in th WA larsen ice sheets.

Unfortunately for their predictions GRACE is an ongoing satellite programme and the current updated symmetry observes the opposite.

We estimate mass trends over Antarctica using gravity variations observed by the Gravity Recovery and Climate Experiment (GRACE) satellite mission during its first 3.5 years (April 2002–November 2005). An image of surface mass trends is constructed from 1° × 1° pixels over the entire continent, and shows two prominent features, a region of mass loss along the coast of West Antarctica, and one of accumulation in East Antarctica. After adjusting for bias due to smoothing and to GRACE's limited spatial resolution, and removing post glacial rebound (PGR) effects, the rate in West Antarctica is −77 ± 14 km3/year, similar to a recent estimate of ice mass loss from satellite altimetry and remote sensing data. The prominent East Antarctic feature in the Enderby Land region has a rate of +80 ± 16 km3/year.

So we see decreasing icemass in the Arctic summer and increased icemass in the Antarctica polar region.

A further study published this week at Boston University and to be published in science suggests symmetry due to the cyclical progression of the earth and the three phase changes of (obliquity, precession, and eccentricity)

Through dated geological records scientists have known for decades that variations in the Earth’s orbit around the sun – subtle changes in the distance between the two – control ice ages. But, for the first 2 million years of the Northern Hemisphere Ice Age there has always been a mismatch between the timing of ice sheet changes and the Earth’s orbital parameters.

A new model of ice volume change developed by Maureen Raymo and Lorraine Lisiecki, researchers in BU's Department of Earth Sciences, proposes a reason for this discrepancy. Like other models, it is consistent with traditional Milankovitch theory – which holds that the three cyclical changes in the Earth’s orbit around the Sun (obliquity, precession, and eccentricity) influence the severity of seasons and high latitude temperatures over time. However, the new model differs from earlier ones in that it allows for a much more dynamic Antarctic ice sheet.

According to the researchers, from 3 million years ago to about 0.8 million years ago, Northern Hemisphere ice volume appears to have varied mostly with the 41,000 year period of obliquity – the periodic shift in the direction or tilt of Earth’s axis. However, summer insolation (incoming solar radiation), which is widely believed to be the major influence on high-latitude climate and ice volume change, is typically dominated by the 23,000 year precessional period – the slow “wobble” of the Earth on its axis.

“We don’t tend to think of ice volume in that region as varying significantly, even on geologic time scales,” said Raymo. “However, only a modest change in Antarctic ice mass is required to “cancel” a much larger Northern ice volume signal.”

Records used to measure the ice volume, such as sea levels, integrate the whole world. According to Raymo, the new model demonstrates that while the precession frequency is actually strong in ice volume changes at each pole, in geologic records, Northern and Southern hemisphere ice volume trends act to cancel each other out at this frequency.

0 Comments:

Post a Comment

Links to this post:

Create a Link

<< Home


Web Counters