Naked Science Forum

Life Sciences => The Environment => Topic started by: Brex on 25/11/2007 14:25:58

Title: What would happen if Global warming completely melted the polar ice caps?
Post by: Brex on 25/11/2007 14:25:58
If global warming caused complete melting of polar icecaps and the ice mass was transferred to oceans at lower latitude would there be a significant lengthening of days by slowing of earth rotation?
Title: Re: What would happen if Global warming completely melted the polar ice caps?
Post by: frethack on 27/11/2007 21:27:56
The effect would be immeasurable.  If you imagine the Earth being represented by an orange then it would only take a couple of drops of water to represent all of the water on, under, and above the crust.
Title: Re: What would happen if Global warming completely melted the polar ice caps?
Post by: JimBob on 28/11/2007 01:21:29
And you would probably drown. Anything below about 200 meters above (present) sea level. Sea level is already several inches higher than it was about 30 years ago.
Title: Re: What would happen if Global warming completely melted the polar ice caps?
Post by: Andrew K Fletcher on 01/12/2007 09:56:53
The thing about the ice that is melting at the caps is that it is floating on the ocean so whether it is frozen or not makes zero difference to the ocean levels, In fact, if you drop an ice cube in a glass of booze, the drink level rises, when the cube melts the level should be the same and if lots of ice is stacked in the glass the ice occupies more space than water so the level should fall rather than rise.

The real cause of rising ocean levels is not the melting ice caps but the suspected rising ocean temperatures. If you take a ¼ pint of cold water in a pyrex measuring jug and heat it so that it becomes too hot to put your finger in but not boiling you will see a marked rise in the water level, so theoretically the ocean levels should rise as the water temperature increases, however because the ocean is a huge volume of water the energy required to heat it up to anywhere near the temperature of our experiment would have to be prolonged and pretty impressive, so at best the ocean surface water will heat up and yes this could increase the ocean level but ever so slightly.

Underwater sources of heat. Another source of ocean’s obtaining heat is from water that is exposed to magma, like the smokers recently featured. Here there is an immense amount of energy that is constantly heating the water and I suspect there are many more areas like these that are yet to be discovered heating the ocean like an element in an electric kettle.

Deserts. The rain no longer falls on the land, although there are artesian wells in the Sahara desert and other deserts that are used to access non-renewable water reserves in place from when rain was more bountiful. The Sahara is larger than the U.S.A. Australia which is a huge desert and semi-desert can be placed 2.5 times into the Sahara Desert if you include a bit of land on the other side of the Suez Canal, but this should give you the picture of the size of the problems caused by deserts and desertification.

The sun is a constant source of energy and let’s assume for now that the evaporation rate from the sun equates to the energy required to heat a kebab and the Earth is the kebab, therefore the heat is spread evenly around the kebab surface so evaporation from the kebab is constant each day providing it remains the same size and contains the same amount of water.

The Earth also is the equivalent of our kebab being roasted under the sun day in day out so assuming the same amount of water becomes airborne each day and the same amount of rainfall occurs somewhere around the globe each day the ocean level should remain constant. However as the deserts have grown to their impressive global 1 third of the earths land mass in a relatively short timescale and we know the rain does not fall on these lands anywhere near as much as it has done in the past, the land mass cannot hold on to any of the water because even if it does rain in these harsh arid areas the surface water quickly runs off into rivers and back into the ocean as flash floods while the remaining rain forests milk the excess moisture from the atmosphere and receive more rain than usual because it is certainly not falling on the massive deserts so it is either falling on the ocean or on the land that still has some tree cover so the cause of rising oceans is not melting ice caps at least while the melting is taking place from water that is frozen and floating on the ocean but is caused by the uneven distribution of atmospheric moisture (cloud cover) and rapid land run off from rainfall.

Andrew K Fletcher
Title: Re: What would happen if Global warming completely melted the polar ice caps?
Post by: JimBob on 01/12/2007 10:25:52
I believe that the thing being forgotten here is that the vast majority of ice cover in Greenland, Spitzenbergen, Antarctica, Northern Canada, Russia, etc. is on LAND. It doesn't float in the ocean. Thus, when melted, sea level rises.
 I am going to find some pictures of Caribbean beach terraces showing these wave cut terraces when sea level was much higher during the latest interglacial period. Back in a moment.
Title: Re: What would happen if Global warming completely melted the polar ice caps?
Post by: JimBob on 01/12/2007 11:20:39
OK. This is Just one example. I have gotten the abstract, an illustration and the conclusions form this research article. The Antarctic ice melting event was a comparatively mild one but raised sea level 20+ meters. This article represents main-stream scientific thinking about what would happen if the ice caps of the world melted. And this event recorded in the Bermudan rocks is a record of a rather minor event in time. A major even could cause a 200+ meter rise in sea level.

(The ages in diagram on the right side are in 1000's of years ago.)
From GEOLOGY, v. 27, n. 4, p.375-378

A +20 m middle Pleistocene sea-level highstand (Bermuda and the
Bahamas) due to partial collapse of Antarctic ice


P. J. Hearty, P. Kindler, H. Cheng, and R. L. Edwards

Chertsey 112, Box N-337, Nassau, Bahamas

Marine deposits at +20+ or -3 m on the tectonically stable coastlines of Bermuda and the Bahamas support the hypothesis of a partial collapse of the Antarctic ice sheet during the middle Pleistocene. Beach sediments fill a sea cave at +22 m in Bermuda, and horizontal, fenestrae-filled beds crop out on platforms at two sites as high as +21 m in Eleuthera, Bahamas. Carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment. Amino acid racemization and TIMS (thermal-ionization mass spectrometry) dates constrain the age of the deposits to between 390 and 550 ka, while proxy evidence supports a correlation with oxygen isotope stage 11. This direct geologic evidence of a 20% decrease in polar ice during the middle Pleistocene has important implications for the stability of ice sheets during warm interglaciations



Our multiple-method data set confirms that intertidal sediments were
deposited at +20 ± 3 m at three tectonically stable sites in Bermuda and the
Bahamas at the end of a long, warm, and complex interglaciation, at or
before 420 ± 30 ka.

In order to account for a 20 m increase in ocean volume, if all of
Greenland and West Antarctic ice (~12 m) melted, an additional 8 m water
equivalent of East Antarctic ice must have also melted.

We suspect that prolonged warm interglacials may have a deleterious
effect on the stability of ice sheets, particularly the West Antarctic ice sheet,
which might be decoupled from its base by warming and rising seas and
changing basal-till conditions.

This flooding of the world’s oceans must have initiated a dramatic revamping
of low-island ecosystems during the middle Pleistocene. If it can
be established that warm and prolonged interglaciations have a causal link
with the stability of ice sheets, then the implications of present-day global
warming for heavily populated, low-lying coastal areas are profound.
Note added in press: In Bermuda, we discovered a second, larger sea
cave in Government Quarry. Its stratigraphy parallels that of Figure 2.
A shelly, marine conglomerate at +18 m is coarser and thicker, and is overlain
by a 35-cm-thick flowstone. We infer that this lower cave filled first,
then became inactive as sea level continued its rise to the +21 m level.

Title: Re: What would happen if Global warming completely melted the polar ice caps?
Post by: Andrew K Fletcher on 01/12/2007 15:30:48
Didn't forget that Jim, just relating to the curent ice melts which are floating sheets of ice and therefore cannot change the ocean level. A total ice melt would as you state cause a significant rise in ocean levels but the recent melts cannot alter the ocean levels in the slightest.

My experiment with a glass filled with ice cubes and a little water, recording the level with blue tack revealed that when the ice melted the level remained exactly the same. However after I popped round next door and returned, I was staggered to find the water level had risen in the glass, after scratching my head and trying to explain what had happened to my son, I turned around and asked my wife if she had altered the level as a joke. Her grinning face revealed all and she admitted to adding a drop of water just to confuse me :)

I believe that the thing being forgotten here is that the vast majority of ice cover in Greenland, Spitzenbergen, Antarctica, Northern Canada, Russia, etc. is on LAND. It doesn't float in the ocean. Thus, when melted, sea level rises.
 I am going to find some pictures of Caribbean beach terraces showing these wave cut terraces when sea level was much higher during the latest interglacial period. Back in a moment.
Title: Re: What would happen if Global warming completely melted the polar ice caps?
Post by: Andrew K Fletcher on 01/12/2007 15:39:18
Another consideration is that if more water enters the ocean, there is an inevitable increase in weight pushing down on the ocean floor. This may deepen the ocean somewhat and counter the rising ocean levels of a full melt.
Title: Re: What would happen if Global warming completely melted the polar ice caps?
Post by: JimBob on 01/12/2007 17:24:50
Andrew, this point is that there is land ice melting as well as sea ice RIGHT NOW! That is why there has been a 3-4 inch rise along low-lying coastlines in the last 10-20 years.

(It is more noticeable along the low--lying coastlines)
Title: Re: What would happen if Global warming completely melted the polar ice caps?
Post by: JimBob on 01/12/2007 19:01:35
The most worrying part of all of this data is that it is increasing dramatically and exponentially. The likelyhood that in 20-30 years half of London and New York will be flooded. It is even worse for places like Venice.

And here are a few references to this: (all bold is mine.)

ScienceDaily (Sep. 24, 2007) — On the world's coldest continent of Antarctica, the landscape is so vast and varied that only satellites can fully capture the extent of changes in the snow melting across its valleys, mountains, glaciers and ice shelves.

In a new NASA study, researchers using 20 years of data from space-based sensors have confirmed that Antarctic snow is melting farther inland from the coast over time, melting at higher altitudes than ever and increasingly melting on Antarctica's largest ice shelf.

With a surface size about 1.5 times the size of the United States, Antarctica contains 90 percent of Earth's fresh water, making it the largest potential source of sea level rise. It is also a place where snow melting is quite limited because even in summer, most areas typically record temperatures well below zero.

Nevertheless, NASA researchers using data collected from 1987 to 2006 found snow melting in unlikely places in 2005: as far inland as 500 miles away from the Antarctic coast and as high as 1.2 miles above sea level in the Transantarctic Mountains.

AND ----

ScienceDaily (May 15, 2007) — A team of NASA and university scientists has found clear evidence that extensive areas of snow melted in west Antarctica in January 2005 in response to warm temperatures. This was the first widespread Antarctic melting ever detected with NASA's QuikScat satellite and the most significant melt observed using satellites during the past three decades. The affected regions encompass a combined area as big as California.

Son Nghiem of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and Konrad Steffen, director of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado, Boulder, led the team. Using data from QuikScat, they measured snowfall accumulation and melt in Antarctica and Greenland from July 1999 through July 2005.

The melting occurred in multiple distinct regions, including far inland, at high latitudes and at high elevations, where melt had been considered unlikely. Evidence of melting was found up to 560 miles inland from the open ocean, farther than 85 degrees south (about 310 miles from the South Pole) and higher than 6,600 feet above sea level. Maximum air temperatures at the time of the melting were unusually high, reaching more than 41 F in one of the affected areas. They remained above melting for approximately a week.

"Antarctica has shown little to no warming in the recent past with the exception of the Antarctic Peninsula, but now large regions are showing the first signs of the impacts of warming as interpreted by this satellite analysis," said Steffen. "Increases in snowmelt, such as this in 2005, definitely could have an impact on larger scale melting of Antarctica's ice sheets if they were severe or sustained over time."

The satellite's scatterometer instrument sends radar pulses to the ice sheet surface, measuring the echoed pulses that bounce back. When snow melts and then refreezes, it changes to ice, just as ice cream crystallizes when it is left out too long and is then refrozen. QuikScat can differentiate this icy fingerprint in the snow cover and can map on a continental scale the extent of strong snowmelt over the subsequently formed ice layer. Available ground station measurements validate the satellite result.

The 2005 melt was intense enough to create an extensive ice layer when water refroze after the melt. However, the melt was not prolonged enough for the melt water to flow into the sea.

"Water from melted snow can penetrate into ice sheets through cracks and narrow, tubular glacial shafts called moulins," Steffen said. "If sufficient melt water is available, it may reach the bottom of the ice sheet. This water can lubricate the underside of the ice sheet at the bedrock, causing the ice mass to move toward the ocean faster, increasing sea level."

Changes in the ice mass of Antarctica, Earth's largest freshwater reservoir, are important to understanding global sea level rise. Large amounts of Antarctic freshwater flowing into the ocean also could affect ocean salinity, currents and global climate.

Nghiem said while no further melting had been detected through March 2007, more monitoring is needed. "Satellite scatterometry is like an X-ray that sees through snow and finds ice layers beneath as early as possible," he said. "It is vital we continue monitoring this region to determine if a long-term trend may be developing."

QuikScat data are helping scientists better understand how Antarctica and Greenland's ice sheets gain or lose mass. "We need to know what's coming in and going out of the ice sheets," Nghiem said. "QuikScat data, combined with data from NASA's IceSat and Gravity Recovery and Climate Experiment satellites, along with aircraft and ground measurements, all contribute to more accurate estimates of how the polar ice sheets are changing."

The study, "Snow Accumulation and Snowmelt Monitoring in Greenland and Antarctica," appears in the recently published book "Dynamic Planet."

ALSO ----

ScienceDaily (Sep. 26, 2007) — A new NASA-supported study reports that 2007 marked an overall rise in the melting trend over the entire Greenland ice sheet and, remarkably, melting in high-altitude areas was greater than ever at 150 percent more than average. In fact, the amount of snow that has melted this year over Greenland could cover the surface size of the U.S. more than twice.

Marco Tedesco, a research scientist at the Joint Center for Earth Systems Technology, cooperatively managed by NASA's Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland at Baltimore County, used satellite data to compare average snow melting from 1988-2006 with what has taken place this summer.

He found that in high altitude areas over 1.2 miles above sea level, the melting index -- an indicator of where melting is occurring and for how long - was significantly higher than average. Melting over those areas occurred 25-30 days longer this year than the observed average in the previous 19 years.

"When snow melts at those high altitudes and then refreezes, it can absorb up to four times more energy than fresh, unthawed snow," said Tedesco. "This can affect Earth's energy budget by changing how much radiation from the sun is absorbed by the Earth versus that reflected back into the atmosphere. Refrozen snow can also alter the snow density, thickness and snow-water content." Tedesco's findings were published Sept. 25 in the American Geophysical Union's Eos newspaper.

Researchers determine the melting index by multiplying how long melting took place by the area where the increased melting took place. According to Tedesco, melting in April and May of this year in high-altitude areas was very low, but in June melting jumped unexpectedly and led to the record melting index for the year.

"This record melting index in those areas came as a bit of a surprise, showing us, once again, the extreme variability and complexity of these processes," said Tedesco. His expertise in documenting melting trends produced other recent studies on increased snow melting over Greenland and the Antarctic.

The data collected by the Special Sensor Microwave Imagers on the Defense Meteorological Satellite Program satellites provided Tedesco with insight into how much of an electromagnetic signal was naturally emitted by snow and ice in areas beneath the satellite overpass. The microwave instruments can detect melting above and below the snow surface. The data were processed at the National Snow and Ice Data Center in Boulder, Colo., in just 24 hours after the satellite overpass, enabling Tedesco to quickly spot changes that could signal a melting trend or new record.

Tedesco's work also confirmed that the melting index this year in lower altitude areas of Greenland, though not record breaking, was higher than average by 30 percent, placing 2007 in fifth place for the highest melting index after 2005, 2002, 1998 and 2004, in that order.

"Increases in the overall melting trend over Greenland have an impact that stretches beyond its icy shores," said Tedesco. "Aside from contributing to direct sea level rise, melting especially along the coast can speed up glaciers since the meltwater acts like a lubricant between the frozen surface and the bedrock deep below. The faster glaciers flow, the more water enters the ocean and potentially impacts sea level rise."

Tedesco, along with U.S. and European colleagues, plans to combine satellite data with related climate model results. He plans to visit Greenland in 2008 to compare his findings from space-borne data with those obtained by ground-based sensors, all with an eye to gathering further clues of what is happening on Greenland.
Title: Re: What would happen if Global warming completely melted the polar ice caps?
Post by: Andrew K Fletcher on 02/12/2007 20:16:37
Take a 1/4 pint of water cold water in a jug, warm in microwave and watch the level rise. A warming ocean (and it is warming) will produce the rises in ocean level observed with or without melting ice caps... in 1992 I was shouting this from the roof tops along with the problem with expanding deserts, flash floods, pollution, Even did some press conferences and when I realised people at that time would rather have their head up their own ass than consider the planet was in any danger so I wrote a poem setting out where we were heading globally. I do have some answers but I will probably have been dead 100 years before someone decides to sit up and take note. By which time we will have screwed up so bad nothing can be done.

I have written to the UNEP on numerous occasions and been ignored mostly although they have responded a few times with the usual fob offs.

It makes me so bloody angry! This is my planet also and I take umbrage with idiots pretending to address this dire situation by trying to tax global warming and blaming airborne pollution and emissions when the real problem is land management.

We will by no means be the first to screw up our environment. The dinosaurs did it without aircraft, war and road traffic simply by removing the vegetation from the coastlines and they were very good at removing vegetation, perhaps not as efficient as the two legged termite and his chainsaw followed by farming and overgrazing with the odd toxic herbicide thrown in for good measure.

The only way out of this is to reforest the coastlines of the hottest places on earth and then and only then will we begin to see more airborne moisture blocking out the sun where it is currently cooking the soil and surrounding air. The deserts are the key to solving this dash to Armageddon and you can’t bomb the deserts into submission either, in fact we in the west need to realise that the Arab nations and African Nations are going to be our saviours so we should start communicating with them and hope they have a short memory. 

Andrew K Fletcher