Friday, August 7, 2015

Weekend Rebel Science Excursion - 47

New meaning given to R & D
I missed the televised political competition to see which clown could persuade the most fools about the most irrelevant and non-scientific issues facing civilization as we know it.

Instead, I have been rendered aghast at how many scientists, activists, and bloggers (including me) missed some critical science concerning sea level rise change.

The gist of it is that sea level is both rising and falling, depending on location on the globe of the Earth.

In the scientific literature, ignoring those factors of sea level change has, for decades, caused strange contemplations of such things as "the European Problem" (see the video below).

The actual problem was that oceanographers and climate scientists were, for the most part, clueless about what was going on before them, in that case, hidden in very plain sight.

One effort to avoid being blind-sided by overly-specialized disciplines, which can create scientific myopia, is Sackler Colloquia:
The Fingerprints of Sea Level Change

This meeting was held March 31-April 2, 2011 at the AAAS Auditorium, in Washington, D.C. and was organized by Rita Colwell, Christopher Field, Jeffrey Shaman, and Susan Solomon

Meeting Overview

Climate science is addressing issues that require an increasingly interdisciplinary perspective, posing new challenges to scientists and to the organization and support of this science. Like other interdisciplinary activities, recognition and support of interdisciplinary climate science by the broader scientific community—including university and government administrators, journal editors and reviewers, and funding agencies—is advancing slowly. Often it is easier to recognize ideas that would represent major advances within a discipline, than ideas that would provide major advances but cut across multiple disciplinary foundations. This circumstance poses a challenge to interdisciplinary research and may slow interdisciplinary scientific advances. Such issues are of particular significance for studies of climate impacts, which may, for example, represent linkages between physical and social science, as well as feedbacks among physical, chemical and biological systems.

This Sackler Colloquium will provide a forum for addressing these issues. Specifically: How are high-quality interdisciplinary scientific ideas best recognized and nurtured in their nascent phase? How can we improve this recognition process so as to better support interdisciplinary climate science advances? The colloquium will examine the history of successful, innovative interdisciplinary scientific advances, drawing on experience not only in climate science but also in other fields. The purpose of the colloquium is to identify patterns in the evolutions of research in these areas. Are there common characteristics and/or principles that allowed critical efforts to succeed, thereby leading to significant advances? Did they begin as small concepts or as big, break-out ideas? How were these efforts nurtured, supported, or hindered? At what career stages were the primary researchers? How might future, novel interdisciplinary ideas in climate science be better identified?
(Comment on Youtube, emphasis added). Some of these efforts have led to a way of "finger printing" sea level change (e.g. Physics World).

This process is found in the scientific literature (e.g. Estimating The Sources of Global Sea Level Rise).

If sea level change is not considered by public works departments and port authorities, construction and/or improvement of sea ports will experience unexpected problems over time (see e.g. Peak Sea Level - 2, Why Sea Level Rise May Be The Greatest Threat To Civilization - 5).

And in the worse case scenario, Inhofeism (e.g. Inhofe's One Man Troofiness Crusade), people will be deceived into purchasing property in areas that should not be utilized for homes (e.g. Will This Float Your Boat - 3).

Have a good weekend anyway.

Professor Jerry Mitrovica, Harvard University:



Thursday, August 6, 2015

The Methane Hydrate / Clathrate Controversy

Methane Hydrate / Clathrate
I. Background

Observers of the warming oceans have considered many impacts which that warming will have.

On one issue, their are two camps, one saying hydrates will substantially contribute to human extinction, and the other saying it will not.

In other words, the verbal battle lines are well defined.

However, we have to look closer if we want to understand the issues.

So let's take a look.

I am not ready to conclude in this post, rather, I am only laying the issue out on the table for consideration at this time.

II. Basic Views of the Two Camps

A. The Clathrate Catastrophe Camp

The Nature Bats Last blog sets forth the near term human extinction (NTHE) position:
By 15 December 2013, methane bubbling up from the seafloor of the Arctic Ocean had sufficient force to prevent sea ice from forming in the area. Nearly two years after his initial, oft-disparaged analysis, Malcolm Light concluded on 22 December 2013, “we have passed the methane hydrate tipping point and are now accelerating into extinction as the methane hydrate ‘Clathrate Gun’ has begun firing volleys of methane into the Arctic atmosphere.” According to Light’s analysis in late 2013, the temperature of Earth’s atmosphere will resemble that of Venus before 2100.
(Nature Bats Last). The "clathrate gun" reference is sometimes called a hypothesis (Clathrate Gun Hypothesis).

B. The "Nothing To See Here, Move Along Folks" Camp 

This camp has some formidable members too, who plainly say that the other camp is a bit over the top:
News stories and Web postings have raised concerns that climate warming will release large volumes of methane from gas hydrates, kicking off a chain reaction of warming and methane releases. But recent research indicates that most of the world’s gas hydrate deposits should remain stable for the next few thousand years. Of the gas hydrates likely to become unstable, few are likely to release methane that could reach the atmosphere and intensify climate warming.
(USGS: Why a Methane Catastrophe Is Unlikely). Ok, we see that distinct debate lines, on a very important subject, have been drawn.

III. The Admitted Unknowns

A. How Much

The USGS indicates that there are no tools with which to determine which source current atmospheric methane comes from:
The atmospheric concentration of methane, like that of carbon dioxide, has increased since the onset of the Industrial Revolution (fig. 5). Methane in the atmosphere comes from many sources, including wetlands, rice cultivation, termites, cows and other ruminants, forest fires, and fossil fuel production (fig. 6). Some researchers have estimated that up to 2 percent of atmospheric methane may originate with dissociation of global gas hydrates. Currently, scientists do not have a tool to say with certainty how much, or if any, atmospheric methane comes from hydrates.
(USGS: Gas Hydrates and Climate Warming, emphasis added). Of the "2 percent" of atmospheric methane in the air we breathe, it is not known how much of it comes from methane hydrates that have broken down and released their caged methane.

B. Lack of Research and Data?

A lot of attention is being paid to the matter, however, some say the science has not yet matured:
In the field of methane emission research today, the Arctic is one of the most important regions worldwide. It is believed that methane occurs there both in the form of gas hydrate in the sea and as free gas trapped in the deep-frozen permafrost. Methane deposits in permafrost and hydrates are considered to be very sensitive in the expansive shallow-shelf regions, because with the relatively low pressures it would only take a small temperature change to release large amounts of methane. In addition, new methane is continuously being produced because the Arctic regions are rich in organic material that is decomposed by microbes in the sediment. The activity of these microbes and thus the biological release rates of methane are also stimulated by increases in temperature. Hence methane emissions in the Arctic have multiple sources. International scientific consortia are now being established involving researchers from various disciplines – chemists, biologists, geologists, geophysicists, meteorologists – which are intensively addressing this problem. No one can yet say with certainty how the methane release in the Arctic will develop with global warming, either in the ocean or on the land. This research is still in its in­fancy.
(World Ocean Review, p. 2, emphasis added). How such an important issue leaves scientists in the dark because of methane clathrate research immaturity is troubling.

C. Jury Still Out?

One good place to observe the dynamic back and forth is a Guardian piece:
Can scientists overcome huge uncertainties to pin down how close, or far, we might be to a tipping point?

About a week ago, climate scientist Michael Tobis wrote a critique of my 'Seven facts about the Arctic methane time bomb' following a twitter exchange with him and Chris Colose, author of an article at Skeptical Science arguing that the core scenario of a new Nature paper by Gail Whiteman et. al on the economic costs of Arctic climate change is extremely unlikely.

Much of this debate kicked off because the said Nature paper advances a hypothetical scenario for an abrupt Arctic methane release over either a decade or several decades of about 50 gigatonnes (Gt), and argues specifically that such a scenario is "likely." My own attempt to understand the literature convinced me that the scenario should be viewed as a serious possibility.

Tobis on the other hand is the latest amongst several scientists offering scathing criticisms of that scenario, which in his own words is "as close to impossible as anything in earth science; actual geophysics refutes it."

He begins with my first point, 1. The 50 Gigatonne decadal methane pulse scenario was posited by four Arctic specialists, and is considered plausible by Met Office scientists.

Tobis writes that the Review of Geophysics paper I cite says
"Arctic thawing may release in excess of 50 GT of C [Carbon], a very serious matter... But Ahmed refers to the paper in support of a very different assertion, that 50 GT of methane would be released... But the paper to which he points says nothing of the sort. I conclude that he doesn't really know what he is talking about. Specifically he has already shown that he is confused about the distinction between methane releases and CO2 releases."
However, the carbon release scenarios from permafrost explored by the paper include both methane and carbon. Here's what the paper says:
"The most important determinant of whether release of frozen carbon happens as CO2 or CH4 [methane] is whether decomposition proceeds aerobically or anaerobically... In anaerobic conditions, a greater proportion of soil organic carbon decomposition is released as CH4, although not all of it necessarily reaches the atmosphere."
Following this paragraph, the paper cites several scenarios for large-scale releases from permafrost carbon, including the 50-100 Gt carbon release I mentioned.
(Why The Jury's Still Out). The jury is out for some people, but not out for others it would seem.

IV. Some Other Scientists Speak Out Boldly

An expert on the Siberian Arctic methane hydrate scenario has published some papers indicating that a serious condition exists:
Extremely high concentrations of methane (up to 8 ppm) in the atmospheric layer above the sea surface along with anomalously high concentrations of dissolved methane in the water column (up to 560 nM, or 12000% of super saturation), registered during a summertime cruise over the ESS in September 2005, were analyzed together with available data obtained during previous and subsequent expeditions to distinguish between possible methane sources of different origin, potential, and mobility. Using indirect evidence it was shown that one such source may be highly potential and extremely mobile shallow methane hydrates, whose stability zone is seabed permafrost-related and could be disturbed upon permafrost development, degradation, and thawing. Further immobilization of stored methane could cause abrupt methane release and unpredictable climatic consequences.
(Geophysical Research Abstracts, by Shakhova et al., PDF; cf this). I will refer to one other scientist before closing:
Paul Beckwith, a climatology and meteorology professor at the University of Ottawa, Canada, is an engineer and physicist who researches abrupt climate change in both the present day and in the paleoclimatology records of the deep past.

“It is my view that our climate system is in early stages of abrupt climate change that, unchecked, will lead to a temperature rise of 5 to 6 degrees Celsius within a decade or two,” Beckwith told me. “Obviously, such a large change in the climate system will have unprecedented effects on the health and well-being of every plant and animal on our planet.”
(The Methane Monster Roars). This year is still struggling to become the record year, by having the lowest Arctic sea ice extent of all other years.

That is, the lowest since the recent record was set in the year 2012 (Arctic Ice Extent: 2015 Struggles For First Place - 2).

V. Conclusion

The Obama Administration's allowing Arctic area drilling to find more of the poison that is threatening civilization was a deadly event, all their promises to cut poison GHG emissions notwithstanding.

Dr. Shakhova camp:



Wednesday, August 5, 2015

Peak Sea Level - 2

Fig. 1 Sea ports of Iceland
According to the graphics and information provided by Professor Mitrovica of Harvard, all of the sea ports in Iceland, shown in Fig. 1, will go dry (see video below).

The same can be said of all the ports in Greenland (Fig. 2).

Not to mention that all of the sea ports in Australia will experience different levels of rise (N. Australia) or fall (S. Australia), or stay at the same level (Mid Australia), depending on their distance from Antarctica (compare Fig. 4 with Fig. 5).

I mention the ports of Iceland and Greenland, not because they are world scale ports
 
Fig. 2 Sea ports of Greenland
now, but because of the plans to build world scale ports in that area.

Navy Rear Admiral Titley revealed that he is aware of plans to build a world class port ("a new Singapore") in the area because in a few years the Arctic sea ice will be substantially gone during the summer, and thus the once-fabled Northwest Passage will be open for sea travel (Has The Navy Fallen, Iceland Building Arctic Port).

Why that is a big deal, he goes on to explain, is because shipping companies can save a lot of time and money by using the Arctic route instead of the Panama Canal route.

Indeed he was correct, because plans for sea ports have been made:
This point was stressed by Professor Qi Shaobin of Dalian Maritime University in China. Opening up the Arctic "will change the market pattern of the global shipping industry because it will shorten the maritime distance significantly among the Chinese, European, and American markets," he told Chinese state media last week.

Fig. 3 Sea Level Fall  Rise @ Greenland
And shipping figures certainly look encouraging. Russian authorities said last week they had already granted permission for more than 370 ships to sail the route this year. In 2012, only 46 ships sailed the entire length of the passage from Europe to Asia, while in 2010 only 4 vessels made the voyage.

In the wake of these figures, several proposals have been announced to take advantage of the expected expansion in Arctic shipping. Iceland is considering plans, backed by German entrepreneurs, to build a major port on its northeastern shores. Similarly, Stornoway Port Authority in Scotland said last month that it was considering building a special port for Arctic ships so they could refuel and discharge cargoes into smaller vessels for onward shipment to Rotterdam, Le Havre, Liverpool, or London. In addition, Valentin Davydants, captain of Russia's Atomflot fleet of nuclear-powered icebreakers, has estimated that 15 million metric tons of cargo will use the full Northern Sea Route by 2021.

It sounds impressive until you realize that 929 million metric tons of cargo were shipped through the Suez Canal by 18,000 vessels in 2011. By that standard, the Northern Sea Route has still got a long way to go in transforming world shipping.

And other issues affect the attractiveness of sailing in Arctic waters. The seas around the North Pole may be losing their summer ice cover, but there is still the ever-present danger of icebergs and drifting slabs of pack ice.
(Climate Change Is Opening the Door to Arctic Shipping, emphasis added). These plans have evidently been made without consulting Professor Mitrovica who says the sea level around Greenland and Iceland will drop as the ice sheets melt.

Fig. 4  Sea ports of Australia
It would seem that the drop in sea level in that area would have an impact on those plans wouldn't it?!

Those ports, and the ocean around Greenland, have already experienced Peak Sea Level, and are now in decline, now falling, because the gravity of the ice sheet weakens as its ice melts and/or calves into the sea.

Australia has a similar but more complex problem.

Its sea ports are at various distances from Antarctica, and it is so large that it looks to have sea ports that experience lower sea levels in its southern tip, but maybe higher sea levels at its northern tip (Fig. 4, Fig. 5).

I don't have to tell you that this complicates the planning of public works and port authority departments of governments.

Nor do I have to tell you that it complicates the work of architects and marine engineers who are working on some of the projects mentioned above.

Fig. 5 Sea level fall / rise Antarctica (see video)
In fact, I probably do not have to tell you that presently it makes that type of professional task an impossibility, for at least two reasons.

One reason is the politics science of "is sea level rising or falling" that will be played out in countries that have powerful climate change deniers in their governments (e.g. the U.S.A. and Australia).

The other problem, of the two I mention today, is that even the scientist community is not yet coordinated on the papers of Professor Jerry X. Mitrovica (see video below) nor his Team (The Mitrovica Group).

When I took a look at the recent paper of Dr. James Hansen et al. I found no references to sea level fall (SLF), nor any mention of the concepts or papers of Dr. Mitrovica, nor his group (A Paper From Hansen et al. Is Now Open For Discussion).

Until there is a meaningful consensus among scientists concerning the Mitrovica hypotheses, which he says are settled science, then engineers and other public works professionals cannot commit to major multi-billion dollar projects that take years or decades to accomplish (The Agnotology of Sea Level Rise Via Ice Melt, Weekend Rebel Science Excursion - 44, Will This Float Your Boat - 10).

Especially when the sea level will continue to be a moving target while they are building sea ports, and afterwards.

They may be, right now, going full steam ahead on many sea port projects totally unaware or totally unconvinced of the future of world sea ports (Why Sea Level Rise May Be The Greatest Threat To Civilization, 2, 3, 4, 5).

The next post in this series is here, the previous post in this series is here.

Professor Jerry X. Mitrovica on the gravity / axis bulge SLR / SLF issues we don't hear about often:



Tuesday, August 4, 2015

Why Sea Level Rise May Be The Greatest Threat To Civilization - 5

RMS Titanic hits Greenland iceberg
I. Background

The subtitle to today's post is "Karma may be made out of water & gravity."

In this series I have been drawing attention to the vessels of Petroleum Civilization.

Petroleum Civilization is the sub-civilization within the overarching Industrial Civilization which is said to have begun circa 1750 (Why Sea Level Rise May Be The Greatest Threat To Civilization, 2, 3, 4).

That is being done in the context of the world's sea ports, through which pass 95% of import / export equipment, goods, commodities, food, fuel, and the like.

In other words, all of the things which current civilization depends on for international sustenance:
"By volume, more than 95 percent of U.S. international trade moves through the nation's ports and harbors, with about 50 percent of these goods being hazardous materials."
(Will This Float Your Boat - 10, quoting NOAA Ports). Without ports there is no more civilization as we have known it (IMO: "Maritime transport is essential to the world’s economy as over 90% of the world’s trade is carried by sea ...").

II. What Will SLR and SLF do?

The focus of the series is the weakness of sea ports, so, initially I focused on their weakness to sea level rise (SLR).

Today, I will add an additional discussion about sea port weakness to sea level fall (SLF).

I will also add the inexorable problem facing public works departments and port authorities.

That problem is the fact that both SLR and SLF produce different SLR / SLF at various locations around the globe.

Thus, the rising at one place will be a falling at another place.

Not only that, those varying sea levels will change constantly, going up or down, as ice sheets continue to melt.

Which means the problem will not go away simply by building a new port (Will This Float Your Boat - 9).

III. What Caused Such A Wacky Science Fictionish Apocalypse?

Many entities engineered Industrial Civilization, however, Oil-Qaeda engineered Petroleum Civilization (Oil-Qaeda: The Indictment).

The result is a civilization that burns all manner of fossil fuels, a civilization that is addicted to those fuels like a heroin drug addict, and a civilization that thereby causes the global warming of the Earth.

Global warming has damaged the global climate system, causing among other things, ice sheets to melt.

The ongoing gravity impact when ice sheet meltwater flows into the sea, or when chunks of the ice sheet calve into the sea, has an impact on local sea level near the ice sheet, as well as on remote sea level way over the horizon.

Normally, the ice sheet creates, in effect, what is a perpetual high tide around the land mass upon which the ice sheet rests.

When the ice sheet loses its mass to the surrounding sea, it also loses the high tide sea level that surrounded it, because the loss of the power of its gravity goes away along with the loss of its ice mass to the sea.

A low tide sea level then becomes the new normal sea level around it.

The details are in two recent Dredd Blog posts (Sea Level Fall: The Forgotten Aspect of Sea Level Rise?, Is A New Age Of Pressure Upon Us? - 7).

Those posts, along with the video, indicate that the sea levels of the world are now in flux, going up here, but going down there, all at the same time all around the world.

It is an engineering nightmare for any engineers who would build new ports to replace the current doomed ports.

IV. Existing Ports Are Dinosaurs

Most ports are many years old, some many centuries old, all built at the sea level of their time (which had not changed much at all until 1750 on, until our time).

All of those port sea levels are going to increasingly change one way or another in our time, except for a very few that will not be impacted in this crazy ice sheet melt scenario.

The amount of up, down, or very rarely unchanged, will be "determined" by individualized local political bodies in some cases.

Some of them will inexplicably deny the reality floating around their neighborhoods, as some already have (Social Dementia Causes Heated Misunderestimations - 2, Inhofe's One Man Troofiness Crusade).

But, the facts are that the overwhelming majority of ports are going to drown or dry up, as either SLR or SLF impacts their sea port.

V. Conclusion

I plan to monitor the cacophony that evolves following President Obama's "there is such a thing as too late," which he expressed as he began a process of diminishing GHG emissions in the U.S.

One can only wonder if he realizes that the United States is targeted by both Greenland and Antarctica ice sheets in this death spiral process (Greenland & Antarctica Invade The United States, 2, 3)?

He does not seem to be fully aware of what is going on, because he assisted Oil-Qaeda to drill for more fossil fuels in the very dangerous clathrate and methane hydrate infested Arctic Ocean area (Barry & Oil-Qaeda vs Arctic Wilderness, 2).

Doing so this late in the game is a murderous endeavor (Oil-Qaeda & MOMCOM Conspire To Commit Depraved-Heart Murder).

The previous post in this series is here.

Professor Jerry X. Mitrovica on the gravity of the situation which we don't hear about often enough:

05:00 ... an ice sheet has mass and gravity, so it has a gravitational effect on the sea water around it.

18:15 ... if glaciers melt in Alaska, sea level around Alaska will drop.

14:20 ... the scientific literature points out that sea level does not rise nor fall the same all around the globe (scientists have called it "the European problem"). 

19:15 ... analysing unevenness of SLR / SLF informs which ice sheet is melting (e.g. in Greenland or in Antarctica).



Monday, August 3, 2015

Sea Level Fall: The Forgotten Aspect of Sea Level Rise?

Fig. 1 Climate Change and Sea Level
I. Background

Regular readers know that I have been putting a lot of research and writing into the subject of sea level rise (SLR) this year.

That is not to imply that I haven't written anything at all about SLR in years past (e.g. Will This Float Your Boat?, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11; May 2011 -  May 2015).

What I have not focused on is sea level fall (SLF).

While researching the issue, while developing software to calculate future SLR, and while urging more attention to SLR, I just had an epiphany today.

I seems to be science fiction at first blush, but the epiphany is this: regarding the Greenland and Antarctic ice sheets, unless we have had an SLF, we cannot yet have had an SLR.

That is, unless the science team that I wrote about on Friday has presented an invalid hypothesis (Is A New Age Of Pressure Upon Us? - 7).

II. The Issue of Gravity Loss @ Greenland & Antarctica

Take a careful look at Fig. 1 and Fig. 2, as well as the posts they link to, because they show that both SLF and SLR are one of the results of melting ice sheets.
Fig. 2 Axis Upheaval

That is, Fig. 1 and Fig. 2 show a fall in sea level around both Greenland and Antarctica as a result of the loss of gravity caused by the loss of ice mass on those two ice sheets.

And of all things, like I wrote about in Friday's post, quoting the science team that works on this physics oriented aspect of SLR / SLF, when the ice sheet of West Antarctica (WAIS) melts, the resulting SLR of 4 ft. will manifest at, of all places, the coasts of the United States!

Not only that, the same thing happens to the U.S. when the ice sheet at Greenland melts (Greenland & Antarctica Invade The United States, 2, 3).

Double whammy!

III. The Gravamen of the Situation

We must with all dispatch determine if the science in the hypothesis of Professor Jerry X. Mitrovica et al. is correct (see video below).

We must determine if the SLF around Greenland and Antarctica can be detected, and if not, why not.

Fig. 3 Alaska SLF
GRACE, the satellite, has already shown that there is detectable gravity loss in the WAIS.

There is SLF around Alaska where glaciers along with their gravity have vanished into history (Southern Alaskan Sea Level Fall).

The ice shelf floating on the ocean around Antarctica may be a deterrent to detecting SLF there, but there are open water areas around Greenland where that is not the case (e.g. Baffin Bay).

Check it out dear scientists and/or readers.

IV. The Potential Consequence of Not Knowing

There would be no loss of gravity if all the meltwater was going into the huge canyons and river systems beneath both Greenland and Antarctica (The Surge: A Forgotten Aspect of Sea Level Rise).

Which means that at any time whatever is damming the meltwater, whatever is preventing it from reaching the sea, is keeping the gravity there above the land (water has mass, ergo gravity).

Which could set up a "pulse 1C" type of event.

A surge (or "pulse") in this case is a sudden release of meltwater when an obstruction gives way letting all the gravity and water flow into the sea away from the land:
However, meltwater pulse 1C (8,200-7,600 years ago) left traces at numerous locations in the United States, northwestern Europe, and China. It occurred soon after the 8200 year cold event, which resulted from the final catastrophic drainage of glacial Lakes Agassiz and Ojibway around 8400 years ago. The torrent of around 100,000 cubic kilometers unleashed within a few years or less amounted to barely a meter rise in global sea level, if evenly spread across the world's oceans (note 1). Yet the stratigraphic record preserves vestiges of this relatively minor pulse.
(The Surge: A Forgotten Aspect of Sea Level Rise, cf. Weekend Rebel Science Excursion - 45). SLF is the hidden gorilla in the SLR room, and it should be studied forthwith.

V. Conclusion

Somebody has to do it.

In the next few days or so I am upgrading my SLR calculation software to also deal, in some way, with the concept of gravity induced SLF (unless comments by regular readers have valid contra information).

Professor Jerry X. Mitrovica on the gravity / axis bulge SLR issues we don't hear about often enough:

05:00 ... an ice sheet has mass, so it has a gravity effect on the sea water around it.

18:15 ... if glaciers melt in Alaska, sea level around it will drop (see Fig. 3 above).

14:20 ... the scientific literature points out that sea level does not rise nor fall the same all around the globe (it is called "the European problem"). 

19:15 ... unevenness of SLR / SLF informs which ice sheet is melting (e.g. in Greenland or in Antarctica).