Guest post by Jim Steele, director emeritus Sierra Nevada Field Campus, San Francisco State University.
Based on NOAA’s 2014 Arctic Report Card, the past 2 decades of ice loss in Greenland has slowed dramatically in 2013-2014. In contrast to Velicogna’s (2014) previously published average mass loss of 280 +/-58 gigatons/year using GRACE satellite data, or the maximum loss of 570 gigatons in 2012-2013, there was only an insignificant loss of 6 gigatons from June 2013 to June 2014, or mere 1% of the previous year’s loss. A loss of 360 gigatons translates into a 1 millimeter rise in sea level, therefore the 2013-2014 sea level rise should be 1.3 mm less than the year before. And based on historical analyses, Greenland will likely begin gaining mass in the coming years.
In Vanishing Ice Most Likely All Natural (transcipt here) I argued that Greenland’s glaciers would soon stabilize and sea ice in the Barents Sea would soon recover based on trends in the transport of warm Atlantic water into the Arctic. Although a one-year recovery is much too short a period from which to derive reliable projections, it is exactly what natural climate dynamics predict.
Based on GRACE satellite gravity estimates (illustrated in the graph below on the left) and hydrographic measurements (graph on right), Greenland’s lost ice has correlated best with the pulses of warm Atlantic water that entered into the Irminger Current that flows to the west around Greenland, delivering relatively warm water to the base of Greenland’s marine terminating glaciers. (Temperatures of the Irminger warm pulse are represented by the numbers graph on the right.) Marked by the red arrow most of Greenland’s ice loss has happened in the southeast region, precisely where the brunt of warm subsurface waters entered the Irminger Current. Accordingly Kahn (2014) reported between 2003 -2006 that 50 % of the total ice loss of the Greenland Ice Sheet occurred in southeast Greenland, and thinning and calving of just 2 glaciers (marked HG) and (KG) accounted half of that loss. Thinning and calving are driven primarily by submarine melting. Although NOAA highlights Greenland’s surface melt rates, Rignot (2009) report that rates of iceberg discharge and rates of “submarine melting are two orders of magnitude larger than surface melt rates.”
Researchers have measured the inflow of warm Atlantic waters along a line between Scotland and the Irminger Sea (A. below) and have determined how that water was partitioned between flows entering the Irminger Current and the flows entering the basins that feed the Barents Sea. Using satellite altimetry to measure changes in sea level, Chafik (2014) reported the flow of warm Atlantic waters into the Irminger Current had increased significantly between 1992-1998 (B. below), but over the past 18 years the volume of warm water has been declining. Accordingly researchers had reported that large glaciers, like the Jakobshavn with submarine grounding points, had been stable or advancing between the 1960s and early 1990s. Then coincident with the arrival of a warmer water via the Irminger Current, the glaciers abruptly began retreating. Since 1997 the loss of Greenland ice accelerated culminating in the widely trumpeted loss of 570 gigatons in 2012-2013, which was opportunistically portrayed as evidence of CO2 warming.
Because the inflow of warm water has been waning since the late 1990s, it suggested that accelerated loss of ice would soon wane as well. Based on the drop in sea level (B. above) the volume of intruding warm Atlantic water has decreased by 10%. If the previous pulse of warm water has been the driving force for retreating Greenland glaciers and melting Barents Sea ice, then that reduced inflow predicts Greenland’s glaciers should soon stabilize while Barents Sea ice begins to recover. Indeed 2014 also witnessed an increase in Barents Sea ice. Likewise NOAA’s 2014 Arctic Report card also stated the “coverage of multiyear ice in March 2014 increased to 31% of the ice cover from the previous year’s value of 22%.” Suggesting more ice is surviving the melt season. In addition the mean sea-ice thickness in multiyear ice zone along northwest Greenland has increased by 0.38 m.
But why did the loss of Greenland ice continue to accelerate after the initial 90s pulse of warm water intrusions? The warm intruding Atlantic water is saltier and denser and flows between 100 and 900 meters below the surface. The weight of the glaciers have depressed the continental shelf so it slopes towards the shore (similar to the condition illustrated below for Antarctica’s Amundsen Sea glaciers.). When pulses of warm water are strong enough to rise over the shelf’s outer ridge, that warm dense water then flows downward to the grounding point of the glacier and remains there until a new equilibrium is established via basal melting and a retreating grounding point. Increased basal melting also increases calving of the floating ice shelf and the loss of buttressing power that inhibits the glaciers’ seaward flow. The end result is the glaciers accelerate seaward, causing dynamic thinning, increased calving, and a large loss of ice mass that continues until a new equilibrium is established. The continued reduction of warm water inflows and the dramatic reduction of lost ice mass in 2014, now suggest the glaciers are no longer adjusting to the previous warm water intrusions.
Before the Little Ice Age (LIA), Greenland’s glaciers, like the Jakobshavn, were smaller than seen in the present day (Young 2011). During the Little Ice Age between ~1400 and 1850, glaciers grew to their maximum Holocene extent. That LIA advance correlates with 1) lower solar flux, 2) decreased inflows of warm Atlantic water, and 3) a more persistent negative North Atlantic Oscillation. Although topographical features of Greenland’s glaciers will cause each glacier to adjust in a unique manner, overall the recent decrease in solar flux approaching LIA levels, the current decline in warm water inflows, and the current trend to a more persistent negative North Atlantic Oscillation all suggest that Greenland will begin accumulating ice mass over the next decade.
In Ocean Gyre Circulation Changes Associated with the North Atlantic Oscillation (NAO)
Curry (2001) created a Transport Index illustrating the correlation between the pole-ward transport of warm tropical water and the North Atlantic Oscillation. As seen in their illustration, there was a rapid increase in the pole-ward transport during the 80s and 90s when the NAO was in an increasingly positive phase. In general agreement but supplemented by other atmospheric dynamics, Barrier (2014) suggest increased transport is due to the spin-up of the subtropical gyre during the persistent positive NAO and reduced transport follows a spin-down during persistent NAO- conditions.
So why didn’t Greenland’s glaciers begin retreating earlier during the 1980s and 90s? When the NAO is positive, both the sub-Tropical gyre (STG in the illustration below) and the sub-Polar gyre (SPG) speed up and expand. While the spin-up of the sub-Tropical gyre transports more tropical water pole-ward, in contrast the expanded sub-Polar gyre limits how much warm water will enter the Arctic seas. This quasi-blocking effect causes more warm water to be re-circulated equator-ward and stored in the sub-Tropical gyre. The amount of warm water entering the Irminger Current is particularly limited because the sub-Polar gyre also shunts the pole-ward transport to the east towards the Barents Sea. When the NAO first enters a negative phase the sub-Polar gyre contracts towards the west, allowing more warm water to enter the Irminger Sea.
Statistical studies have debated the correlation between retreating Arctic ice and the negative NAO because it generates a confounding short term warming trend that is contradicted by the longer cooling trend suggested for the LIA as well as observed during the 1960s and 70s. But that contradiction is easily explained by the effects of an expanding and contracting sub-Polar gyre (SPG). The initial contraction of the SPG during the early negative NAO allows more warm water to enter the Arctic. However the negative NAO also implies a spin-down of the subtropical gyre and therefore a drop in the pole-ward transport of warm tropical waters. Thus as the negative NAO persists, the initial warm pulse into the Arctic is exhausted and followed by cooling trend decades later. A similar scenario was reported by Bengtsson (2004) in The Early Twentieth-Century Warming in the Arctic—A Possible Mechanism to explain the rapid 1930s and 40s warming of the Arctic and retreat of Greenland glaciers that persisted into the early phase of the negative NAO. With all things considered, the evidence strongly suggests we will soon witness a similar natural cycle and a rebound in the Greenland’s ice.
The essay is adapted and updated from Landscapes and Cycles: An Environmentalist’s Journey to climate Skepticism.
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Won’t glaciers melt as long as the warming trend since the mid-1800’s continues … and isn’t it impossible to know in advance how long that warming will continue … except to look at ice core climate proxies and wild guess ‘hundreds of years”?
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On the other hand, 2013 and 2014 could be the first two years of a new global cooling trend, and we could even be headed for another ice age. That frightens me because my home state of Michigan used to be under one to two miles of ice … and I don’t know how to ice skate.
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But seriously folks, why is it that people love to get attention by predicting the future, and others actually listen to those predictions as if they are accurate? I just don’t get it.
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Don’t we already get enough inaccurate predictions from the climate astrologers and their computer game models?
@richard Greene who says “why is it that people love to get attention by predicting the future
That is a bizarre question. So let me reply with 3 points.
1. The benefits of science comes from providing a theory or model of how stuff works. But anyone can make a model based on past correlations. A model’s value depends solely on how well it extrapolates into the future. Thus to test any model we must make predictions. If you do not understand that, you do not understand science.
2. I suspect in one way or another we have all made predictions and were right, but sadly we were right for all the wrong reasons, and were mislead later on. So it is important to describe the mechanisms and chain of causation that will lead to the predicted results. I predicted increased glacier mass on Greenland driven by a reduction in the poleward flow of warm Atlantic water. To test my model of how climate affects Greenland’s glaciers, the chain of causation must also be tested.
3. I indeed want to call attention to models that focus on the redistribution of ocean heat, and natural ocean oscillations. The CO2 crowd argues the changes in the cryosphere are due to rising CO2, but there are other explanations that correlate better with observed trends. Those alternative explanations make different predictions and allow us determine which models more accurately capture reality. So Richard I do not understand why you try to imply that making a prediction is some kind of personal attempt to get attention. Scientists alway makes predictions, that then must be tested, and we know those predictions may fail. Making predictions make scientists more vulnerable to future criticisms if wrong, or if not well thought out, so predictions are not made lightly.
Jim, you could take this tack:
A formula for calculating the deflection of a beam when loaded, something used millions of times a day, is a model. It predicts the deformation of the beam based on the material properties and the load, and how it is positioned on the beam. Most people do not view the formula as a ‘model’ but it is. It predicts future performance.
Having a complicated model does not mean it cannot be written down as a formula with thousands of variables and constants. That is what a computer programme does.
If engineers were forced to use formulas that gave really wrong answers, we would not trust them to design bridges because they would fall down randomly, or all fall down within an unacceptably short time span, or waste vast resources on bridges that were ridiculously strong.
It seems to me climate modelers have managed to convince the general public, through omission and Grubering, that a model is fundamentally different from, say, a store cash register that calculates correct change using a validated formula involving subtraction.
A very complicated, a nested set of formulas and constants assembled into a Giant Formula that doesn’t work cannot tell us whether or not it is necessary to spend trillions of dollars to avoid burning carbon as an energy source. Common sense dictates that we can only spend when we have a validated model (perhaps just a little bit of money to validate the model – I’m flexible).
Tendered bill minus value of goods purchased equals change due. That is a model we can accept. The IPCC-adored climate models, not so much.
If “Grubering” means openly and cynically taking advantage of the “ignorance” of the general public, then we need another word as well. We need a word for the practice of focusing attention on one single rising or falling segment of a natural oscillation and calling it a uniform change which will never end and will lead to catastrophe.
An example would be if someone living by the sea noticed the tide was rising and ran around the town shouting hysterically “O my God it’s a flood we’re all gonna die!”
Thus perhaps the term “TROMGIF” could be used to describe this bizarre practice arising from mental illness or attention-seeking, or both. It stands for “Tide – Rising – O – My – God – It’s a – Flood”.
Re Opluso’s calculation..
If one assumes that the average human weighs 62 kg and the average water content by weight is at least 50 percent, then the ~80 million humans added to the global population this year will retain roughly 2,480,000,000 additional liters of water during their adult lifetimes.
That’s 2.48 cubic kilometres
World’s oceans have a volume of 1,335,000,000 cubic kilometres
[ref http://www.ngdc.noaa.gov/mgg/global/etopo1_ocean_volumes.html%5D
We are going to have to add a lot of people to lower sea levels even a smidgen.
Attention Mr.Modi, Global leaders and UNFCCC: To conserve about 40% of fuel & thereby reduce carbon emissions, to control climate change and global warming, to prevent road crash deaths and save millions of people from pollution related diseases and to reduce 80% of traffic jams, to uplift the downtrodden and reduce economic inequalities etc. for the first time in the world, I POSSESS A WIPO APPROVED, NO-NONSENCE MIRACLE INVENTION. But, is there anybody in India and the world who can help me to dedicate this PANACEA to humankind? Please Mail to: *vthoorun.rcrv@gmail.com *
No-one has yet satisfactorily demonstrated a predictable cause for climate fluctuations. Even if we accumulate several thousand years’ worth of useful observations, we are still just curve-fitting until we understand these phenomena. For all anyone knows, the melting of Greenland’s ice could accelerate next year. If enough people make enough predictions someone is bound to ‘get it right’ and gain a reputation as a prophet.
One thing I will note: if the Greenland melt accelerates, the CAGW lobby will emerge reinvigorated to trumpet our imminent doom — unless we do as they say. They still won’t understand anything, but they will attract more followers.
Sceptical lefty
I agree. Our attempt to understand any phenomena begins with simple curve fitting and theories and models to explain that curve fitting. Several hypotheses are typically offered and linked to mechanisms that could possibly explain the observed relationships. However again the trick is to demonstrate how well those hypotheses extrapolate into the future. I often told my students we learn more from being wrong than right. We can be right for the wrong reasons, but failed hypotheses tell us what is not important. So I encouraged students and everyone to make predictions and let reality winnow out our illusions.
“Statistical studies have debated the correlation between retreating Arctic ice and the negative NAO because it generates a confounding short term warming trend that is contradicted by the longer cooling trend suggested for the LIA as well as observed during the 1960s and 70s.”
The 1970’s saw an increase in positive NAO and the associated increase in La Nina episodes. It also saw the AMO get to its coldest in its last cold mode, and an increase in Arctic sea ice extent.
Despite an apparent general cooling through the Maunder Minimum in GISP, the coldest years in CET in Maunder (1690’s), Dalton (1807-1817), and the equally cold 1836-1845, all register as warmer periods on the GISP proxy. The most rapid rise on CET is from the 1690’s to 1730, GISP goes in completely the opposite direction. Personally I would take the inter-annual noise more seriously than the apparent cooling trend of GISP through Maunder, because it is totally at odds with the very warm 1350-1150 BC in GISP, which had a very marked increase in El Nino, and much cold in the mid latitudes.
http://snag.gy/FdXju.jpg
I think that everyone is aware that a hypotheses may be shown to be false even if it seems to fit the data that we have but I am not going to allow the changing of past data to alter my view of reality,it is important that we keep looking forward if we are ever going to understand how the climate works.If we don’t know what the data was at a previous period then all we can say is that we don’t know but it is ok to speculate about the future because it can be shown to be wrong if it is wrong.