HALF-TRUTHS ABOUT RETREATING GLACIERS

 

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below is the transcript

Welcome back to this examination of Half Truths About Retreating Glaciers in part 6 of How Pressure Systems Control Climate.

There is no question what-so-ever that most of the world's glaciers have been retreating. However because the elites at Climate.gov believe rising CO2 is causing all the earth's warming, they mistakenly assume it iscan also be blamed for retreating glaciers, stating

"the most dramatic evidence that earth's climate is warming is the retreat and disappearance of mountain glaciers around the world."

So, the public is fed half-truths about a CO2 climate crisis causing glacier retreat.

In contrast, there is wealth of opposing, peer-reviewed, published, scientific evidence demonstrating that changing patterns of moisture transport control the ebbs and flows of glaciers - not global average temperature. So here I will share just a small portion of that science for you to follow.

Just consider that Greenland's Jakobshavn glacier retreated by half its length before 1851 during cooler times. Clearly dynamics other than warming are in play, dynamics shamefully downplayed or not discussed at all by mainstream media.

A growing number of scientists have been questioning the dogma that the Little Ice Age's glacier growth and subsequent retreat, was driven by changing temperature. As Norwegian glacier expert Atle Nesje queried

"The Little Ice Age - only temperature?

In that regard climate scientist Michael Mann wrote, "the little ice age was a time of modest cooling of the northern hemisphere by about 0.6 degrees Celsius." those centuries may have been "more significant in terms of increased climate variability."

Climate scientist Christian Vincent questioned why the Alp's glaciers began retreating in early 1800s before any global warming had begun and concluded decreasing winter precipitation caused glacier retreats.

Glaciers can be characterized by two different but intimately linked zones.

The ablation zone is located at the lower end of a glacier, there, snow and ice are lost during the warm summer melt season. So, some scientists argue glaciers are retreating because CO2 global warming is increasing ablation.

At the top of a glacier is the colder accumulation zone where snow and ice are added to a glacier. When there is less replenishment of ice in the accumulation zone due to decreased precipitation, less ice is transported downslope causing the ablation zone to retreat.

Thus, less precipitation can cause retreating glaciers even when temperatures are not warming.

A group of Swiss climate scientists led by HansPeter Holzhauser published that the period of Little Ice Age glacier growth in the Alps (illustrated by black silhouettes) correlated with periods of heavy rainfall and high lake levels (illustrated by the shaded regions)

Three periods of high lake levels corresponded with peak glacier growth while glacier retreats correlated with lower lake levels.

In the paper "solving the paradox of the end of the little ice age in the Alps," Vincent reported that our current retreat of alpine glaciers had resulted from a 25+% decrease in winter precipitation since 1830.

Norwegian glacier expert Atle Nesje argued the North Atlantic Oscillation determines which regions receive glacier sustaining moisture, by shifting the pathways of the moisture- bearing westerly winds.

During the oscillation's negative phase, the Azore High- and Iceland-Low pressure systems weaken and shift southward, diverting moist westerly winds towards southern Europe.

During the positive phase those pressure systems intensify and shift the winds northward towards Scandinavia. In the positive phase, precipitation is diverted away from southern Europe causing its glaciers to retreat, while simultaneously redirecting moisture to the Scandinavian coast where glaciers were growing since 1967.

The North Atlantic Oscillation can shift phases from month to month but on average can favor one phase for decades or centuries.

During the little ice age, the scientific consensus suggests the North Atlantic Oscillation was primarily in its negative phase, accounting for the growing glaciers in southern Europe. But since at least 1920, it has been in the positive phase more often, accounting for the high percentage of retreating Alpine glaciers

Between 1950 and 1980, during a slightly more more negative phase of the oscillation the number of advancing Alpine glaciers increased to over 60%. But with a return to a more positive phase, fewer than 5% of the Alps’ glaciers are now observed advancing and most are retreating.

Due to the surprising denial of precipitation effects on glaciers, politicians and climate crisis promoters argued rising CO2 would cause the extinction of Mount Kilimanjaro’s glacier before 2020.

However, based on past lake levels, such as nearby Lake Naivasha’s, precipitation changes correlate with the ebbs and flows of Kilimanjaro’s glacier.

1000 years ago, during the Medieval Warm Period this region of Africa was much drier than today, and the existing glacier of that time likely disappeared.

Then during the Little Ice Age, coinciding with sunspot minimums the Intertropical Convergence Zone migrated southward, the region experienced increasing rainfall and a new glacier evolved, reaching its maximum area by the late 1700s.

In 2007, glacier expert Douglas Hardy summarized the research indicating Kilimanjaro’s current glacier is only about 50-200 years old, in agreement with the timing of Lake Naivasha’s high stand.

Similarly, research by Cullen (2006) concluded glaciers on Kilimanjaro are merely remnants of a past climate rather than a sensitive indicator of 20th century climate change

Curiously, over the past 4 years as sunspots approach a century low, lake Naivasha’s lake levels have been increasing along with increased snowfall on Kilimanjaro. So, keep an eye out for how Kilimanjaro responds. It certainly hasn’t disappeared as Al Gore or Michael Mann predicted.

By ignoring the precipitation dynamics of previous centuries click-bait media uses graphs like this to suggest the glacier may soon disappear and incorrectly blame CO2 warming.

The climate crisis narratives typically fail to report renowned glacier expert Georg Kaser's 2010 explanation of that decline stating, "the near extinction of Kilimanjaro’s plateau ice in modern times is controlled by the absence of regional wet periods rather than changes in local air temperature on the peak of Kilimanjaro."

A 2019 study led by Kevin Anchukaitis used drought proxy data to determine regions of high rainfall and snowpack (here illustrated in blue) and regions of drought illustrated in brown

They found a strong correlation with weak solar output (the sunspot minimums), the negative phase of the North Atlantic Oscillation and Little Ice Age glacier advances in southern Europe, Alaska, and northwestern North America

When the North Atlantic Oscillation changed to its positive phase, wet regions switched to dry regions, with resulting glacier retreats.

Glacier National Park, on the USA-Canadian border, sits at a pivot point of the North Atlantic Oscillation's wet/dry see saw.

The park's largest glacier, the Sperry, reached its maximum size in the mid 1800s during the wet negative phase. The ensuing drought conditions when the North Atlantic Oscillation switched to its positive phase, caused the Sperry to lose 62% of its area between 1850 and 1945.

Further north, the mysterious retreat of Alaska’s Glacier Bay glaciers highlighted another dynamic.

In 1794 the Vancouver expedition reported the entire bay was covered by a large tidewater glacier with its ocean outlet at Icy Strait choked with ice

Eighty-five years later in 1879, before global warming had begun, John Muir visited Glacier Bay to find the glacier had retreated a whopping 48 miles.

By 1916 the bay's main glacier had retreated an additional 17 miles Why such a rapid retreat in cooler times?

To complicate matters, there are still glaciers that are currently growing despite warmer temperatures.

The Johns Hopkins glacier has been advancing since 1929.

The Margerie glacier flows downslope at a rate of 2000 feet per year where its terminus maintains a stable position by calving ice bergs into the bay.

The Brady Glacier had advanced between 1794 and 1961 and is now relatively stable

The key to understanding these contrasting fluctuations is that the non-retreating glaciers have accumulation zones at elevations above 10,000 feet or 3 kilometers.

Livia Jakob’s 2021 study of glacier behavior in the Gulf of Alaska since 2010 showed contrasting glacier fluctuations were a function of elevation. Glacier Bay is fed by glaciers in the St Elias mountains (shown here in orange)

Glaciers originating in the higher elevation mountains are stable or gaining ice over the past decade as seen by the green trend lines in the St Elias Mountains and the Alaska Range mountains.

In contrast, glaciers at lower elevations are losing ice, the reds and yellow trend lines. Coincidentally, most of the small glaciers that once contributed to the glacier that had filled Glacier Bay and seen during the Vancouver expedition, had accumulation zones below 10,000 feet.

Clearly, in addition to precipitation amounts, glacier growth and retreat are functions of elevation

Why is an elevation of 3 km or 10,000 feet so critical at Glacier Bay?

Snow forms when water vapor freezes and freezing temperatures are typically encountered at 10,000 feet and above. For snow to accumulate on a mountain slope, local air temperatures must remain below freezing all the way to the surface.

However, during the summer, Glacier Bay's average high surface temperatures are above freezing in August through October, just when peak precipitation occurs.

Using a moist lapse rate of 2.7 ºF cooling for every 1000-foot increase in altitude, we can calculate the elevation where snow will accumulate each month.

The minimal freezing elevation for August is 10,300 feet, it's 7,700 feet for September and 4,800 feet in October

Atmospheric rivers carry the bulk of moisture from the tropics to the higher latitudes. Where atmospheric rivers make landfall is determined by the seasonal position of the Pacific’s high- and low-pressure systems.

The more northerly position of the Pacific High-pressure system during summer guides more atmospheric rivers into the Gulf of Alaska during August through October. Accordingly, Glacier Bay's peak precipitation happens during September and October.

But landfall of relatively warm atmospheric rivers has dramatically different effects on snowpack at different elevations. Atmospheric rivers increase snowpack above the freezing elevations but reduce snowpack at lower elevations. The near total reduction of snowpack by a warm atmospheric river, has been well documented from Greenland to California’s sierra Nevada.

Without accounting for elevation freezing points such contrasting effects have caused some correlational studies to mistakenly suggest precipitation has no significant effect on a glaciers overall growth.

The moisture transport to the Himalayan glaciers is more complicated.

The greatest accumulation of ice in the Mount Everest region is driven by summer monsoons. And similar to northwestern North America’s glaciers, El Ninos and La Ninas will cause decadal ebbs and flows of moisture transport to those glaciers.

In contrast, the Karakorum mountains receive little moisture from the summer monsoons but more moisture from the winter westerly winds, causing the Karakorum glaciers to react differently than eastern Himalayan glaciers

Nonetheless, a multitude of researchers such as Shekhar (2017) and Singh 2020. They have reported a long-term drying trend that began in the late phases of the Little Ice Age causing retreating Himalayan glaciers before the rise of industrial CO2.

Climate expert Tapio Schneider's 2014 research described how the Intertropical Convergence Zone migrated southward during the Little Ice Age, weakening the Asian monsoons supply of summer moisture to Himalayan glaciers

Jian Hui Chen's 2019 study detailed, how the north Atlantic oscillation affects moisture transport to the Himalaya. As the Little Ice Age ITCZ and associated pressure systems shifted southward, a wavier jet stream brought more moisture to the Himalaya and Tibetan plateau via the westerly winds.

As solar irradiance rebounded from its depths during the Maunder sunspot minimum, the ITCZ and associated pressure systems began migrating northward, also driving the jet stream northward and reducing moisture transport to the Himalaya.

The interplay of these conflicting dynamics makes it difficult to predict future glacier changes in the Himalaya.

Nonetheless, the politically driven United Nations Environmental Programme, or UNEP argues the decline of Himalayan glaciers are a "clear indicator of [CO2] climate change" and an "obvious indicator of warming temperatures" and they provide this illustration to support their narrative.

However, their bias is immediately obvious.

They illustrate a strong decline in 3 Karakorum glaciers, but just one stable glacier and one that is slightly gaining ice. In contrast, glacier expert Melanie Rankl's 2014 study reported nearly 80% of Karakorum’s glaciers were stable, 5% were advancing and only 7.6% were retreating.

Furthermore, due to a dearth of long-term surveys, most of the Himalayan retreating trends begin around 1960, and that provides the misleading optics used to support a narrative of human-caused CO2 warming. UNEP provides only 2 trends beginning around 1850, and those clearly demonstrate glacier retreats began before global warming.

The United Nations is disturbingly spreading mis-information by not informing the public about the well-documented drying trends that initiated glacier retreat before rising CO2.

But then again, I expect nothing less from an agenda-driven organization that brings a sixteen- year-old actress front and center to brow beat the public about climate science.

Tibet's ancient holy mother, Quomalangma, also known as Mt Everest, further illustrates why retreating glaciers are a function of less precipitation.

As Franco Salerno published in 2015, 75% of Quomalangma's glaciers reside between elevations of 5000 meter (16,500 feet) and 6500 meters (21,300 feet). This happens because atmospheric temperatures do not drop below the freezing point until elevations of 5000 meters and higher.

Glacier accumulation zones are fed by monsoonal moisture peaking in July and August. Accumulation zones must be above 5000 meters as summer monsoonal flows raise the surface temperatures above freezing at 5000 meters. However, measurements reveal precipitation at high elevations was just half of what it had been 20 years before Salerno's study.

That fact led Salerno to conclude their research “Challenges the assumption that temperature is the main driver of glacier mass changes.”

So, what does the future hold for the Earth's glaciers?

Understanding that moisture transport, not global average temperature, controls glacier growth, suggests they are not in crisis

A return to the negative phase of the North Atlantic Oscillation would reverse the retreat of many of the world's glaciers.

Although glacier lengths may shrink, accumulation zones will survive where there is adequate precipitation.

El Nino and La Ninas and other natural oscillations will affect storm tracks causing decadal ebbs and flows of regional glaciers

But the ultimate control will be determined by solar effects on the ITCZ’s latitude and its associated pressure systems. While changes in sunspots and irradiance are unpredictable, the orbital influence of the obliquity cycle suggests the ITCZ will continue to move southward for another 10,000 years causing Little Ice Age-like growth of the world's glaciers.

Up next: part 7: Floods

Why Vanishing Ice Is Likely All Natural?

 (transcript for  video: Vanishing Ice Most Likely All Natural)

A list of reviewed papers used for this presentation available at http://landscapesandcycles.net/shrinkingice.html

Mount Kilimanjaro

If we are to truly prepare for the dangers of climate change and build more resilient environments, we must first understand natural climate change. Unfortunately due to the narrow focus on rising CO2, the public remains ill-informed and fearful about the causes retreating ice. Africa’s Mount Kilimanjaro and America’s Glacier National Park are 2 iconic examples of failed climate interpretations. For example, Al Gore’s “Inconvenient Truth” suggested warmth from rising CO2 had been melting Kilmanjaro’s glaciers. In truth, instrumental data revealed local temperatures have never risen above the freezing point. In 2004, Dr. Geoff Jenkins, Head of the Climate Prediction Programme at England’s Hadley Centre, was prompted by the evidence of no warming, to email the IPCC’s Phil Jones and ask and I quote “would you agree that there is no convincing evidence for Kilimanjaro glacier melt being due to recent warming (let alone man-made warming)?” Yet due to the politicization of climate science, Al Gore shared the Nobel Prize despite perpetuating the global warming myth of Kilimanjaro.

Glacier experts from the University of Innsbruk published and I quote, “The near extinction of the plateau ice in modern times is controlled by the absence of sustained regional wet periods rather than changes in local air temperature on the peak of Kilimanjaro.” Changing patterns of precipitation were recorded in the water level of nearby Lake Naivasha. As researchers documented in this graph, the region had experienced increasing precipitation during the Little Ice Age, followed by a sharp drying trend that began in the late 1700s, which triggered Kilimanjaro’s retreat long before CO2 ever reached significant concentrations. 

Ice structures such as these penitentes, are commonly seen in many high elevation glaciers, and help scientists determine if retreating ice was caused by below freezing sublimation, or melting from warmer air. Over decades, sublimation creates sharp features at the border between sunlight and shade. In contrast, any melting from warm air temperatures oozes across the icy surface destroying those sharp features in a matter of days. So the presence of sharp-angled features like these penitentes, are excellent long term indicators of dry and below freezing temperatures.

Penitentes 

Over 30 years ago I visited Glacier National Park, home of the 2nd iconic example of misrepresented glacier retreat. After thousands of years with less ice, the park’s glaciers grew to their maximum extent during the Little Ice Age. Then they began retreating around 1850. Although the media now hypes the park’s disappearing glaciers as evidence of CO2 warming, the greatest retreats happened long before CO2 could exert any possible effect. In 1913 the park’s largest glacier, the Sperry Glacier was nearly 500 feet thick at a point that would soon become its 1946 terminal edge. By 1936 that thickness had dwindled by 80%. That rapid retreat prompted scientists 70 years ago to predict a natural disappearance of the park’s glaciers. 

As seen here, the contrast between the early and late 20th century retreat is striking. Between 1913 and 1945 the rate of retreat for the Sperry glacier was 10 times faster [due to drought] than rate of retreat since 1979. If rising CO2 has been the driver of recent melting, we would expect an increasingly faster rate of retreat, not slower!  If we are to prepare for changes caused by melting ice, we must view our vanishing ice from a perspective of centuries and millennia, and tht perspective insists that we understand natural climate change.

 There is an abundance of evidence demonstrating that relative to today, far less ice covered the globe during the last 10,000 years, a period known as theHolocene.[i.e. here and here) Far less ice despite much lower CO2 concentrations.

Likewise, although most of today’s average global temperature has been driven by heat ventilating from the Arctic Ocean, as visualized in this NASA graphic, Arctic temperatures were also far warmer during most of the Holocene. Based on changes in tree line, pollen samples and ocean sediments, scientists estimate Arctic air temperatures during the mid Holocene averaged 2 to 7°C higher than today. 

This ice core data from Greenland, exemplifies the Holocene’s changing temperature patterns common for most of the Arctic. But it is a pattern that also corresponds to climate change in many other regions across the globe. After the last Ice Age ended, the period of warmer temperatures between 9,000 and 4,000 years ago has been dubbed the Holocene Optimum. During that time, remnant glaciers from the Ice Age retreated and shrank to sizes far smaller than we witness today. All of Norway’s glaciers completely disappeared at least once, and Greenland’s greatest glaciers, like the Jakobshavn, remained much further inland than now observed. Like many northern glaciers, Jakobshavn had only recently advanced past its present terminus during the unprecedented cold of the Little Ice Age.  

  

Greenland GISP2 Holocene Temperature data vs CO2 trend 

From whale bones, Arctic driftwood, and patterns of Arctic shoreline erosion,we also know that during the Holocene, Arctic summer sea ice retreated 1000 kilometers further north than seen today. Treelines advanced to their greatest northern limits, reaching Arctic Ocean shores 9000 years ago, hundreds of kilometers further north than their current limits.

The paleo-eskimos, or Tuniit, colonized the Arctic’s shoreline about 5000 years ago. They hunted Musk Ox and Caribou with bow and arrow. They lived in tents and heated those tents with Wood. Archaeologists studying Tuniit colonization of Arctic shores, reported periodic abandonment and occupation that corresponded with periods when summer sea surface temperatures bounced between 2–4° cooler and 6°C Warmer than present. Likewise, concentrations of Arctic summer sea ice ranged from 2 months more sea ice to 4 months more open water.

Changes in insolation due to the sun’s orbital cycles, or Milankovitch cycles, correspond with the recent 100,000-year cycles of past major ice ages. We are currently in another warm peak. The Milankovitch orbital cycles also predicted the current cooling trend that began about 4000 years ago. However warm spikes due to high solar output punctuated this cooling trend roughly every thousand years.  The unprecedented Holocene glacier growth during the Little Ice Age occurred when solar output was extremely low.

Past 300 years of solar flux 

In this graph depicting 300+ years of solar flux, the earth warmed as we ascended from the Little Ice Age. Our recent warm spike coincides with high solar flux. However, recently solar output has again retreated, approaching Little Ice Age levels, and correlates with the increasing frequency of cold winters. The next two decades will allows us to evaluate more accurately the effect of these solar changes on climate and glaciers.

The correlation between Greenland ice core data and solar flux, is also seen inScandinavian tree ring data. Tree rings suggest the warmest decade in the past 2000 years, happened during the warm spike of the Roman Warm Periodbetween 27 and 56 AD. After a period of resumed cooling a new warm spike occurred 1000 years ago during the Medieval Warm Period.  After more extreme cooling during the Little Ice Age, a third warm spike peaked around the 1940s.  Most interesting, the consensus from multiple tree ring data sets around the world, also suggest natural habitats were warmer during the 1940s than they are now. Likewise, the greatest rates of retreat for glaciers from Glacier National Park to the European Alps also happened during the 1940s.

The Great Aletsch, the largest and best studied of all the Swiss Alp’s glaciers beautifully illustrates the 3000-year cooling trend punctuated with periodic warm spikes that caused rapid glacier retreats. The Great Aletsch’s maximum length during the Holocene was also reached during the Little Ice age. About 1850 it began retreating to its current position, represented by this baseline. 

However during the warmth of the Bronze Age 3000 years ago, the glacier was Much smaller than today. During the cooler Iron Age the glacier began to grow, but rapidly retreated during the warm spike of the Roman Warm Period. The glacier advanced again almost reaching its Little Ice Age maximum, but retreated rapidly during the warm spike during the Medieval Warm Period.

Great Aletsch: 3000 years of advances and retreats

  During the Little Ice Age, the Great Aletsch advanced to its greatest length of the Holocene, in rhythm with a series of 4 documented solar minimums. Each advance was followed by a rapid retreat, similar to what we observe today,  when solar flux increased.

The glaciers recent retreat does not appear any different from retreats in past. So what does that tell us? To be clear the skeptic argument is not “because it was natural before then CO2 can not possibly contribute today”.

The skeptic argument is simply, we can not determine the sensitivity of our climate and glaciers to rising CO2, until we have fully accounted for past and present natural dynamics. Far too often the media, and a few invested atmospheric scientists, simply assert that retreating glaciers were all natural in the past, but since 1950 the retreat is suddenly due to CO2. But past natural climate dynamics did not suddenly stop operating in 1950. To what degree are natural climate dynamics contributing today? Well, more recent patterns of advancing and retreating ice suggest natural dynamics are the main drivers of today’s retreating ice

A century of mass change measurements for several Swiss glaciers allow us to more finely resolve changes between decades. Again the greatest rate of 20thcentury retreat occurred during the 1930 and 40s, and once again, before CO2 concentration had any significant impact. The rapid 1940s retreat is linked to unusually high solar insolation and patterns of precipitation governed by theAtlantic Multidecadal and North Atlantic Oscillation. 

Swiss Alp glacier advances and retreats

Furthermore when solar flux dipped between the 1960s and 80s, a high proportion of Alpine glaciers, as well as glaciers around the world, stopped retreating and many began to advance as seen here in the Alps.

Changes in solar insolation affect oceans in two critical ways. During high solar output of the Medieval Warm Period, tropical waters in both the Atlantic and Pacific increased by as much as 1°C warmer than today. During the solar minimums of the Little Ice Age, tropical oceans dropped by as much as 1°C degree cooler than today. But equally important changes in insolation affected the volume of warmer tropical waters that were transported toward the poles.

Multiple lines of evidence correlate higher solar activity during the Roman and Medieval Warm Periods, with an increased flow of warm Atlantic water into the Arctic, resulting in reduced sea ice. Conversely, during low solar activity during the Little Ice Age, transport of warm water was reduced by 10% and Arctic sea ice increased. Although it is not a situation I would ever hope for, if history repeats itself, then natural climate dynamics of the past suggest, the current drop in the sun’s output will produce a similar cooler climate, and it will likely be detected first as a slow down in the poleward transport of ocean heat. Should we prepare for this possibility?

Water heated in the tropics is saltier and denser, and when transported into theArctic lurks 100 to 900 meters below the surface. That warm subsurface water can melt sea ice and undermine grounding points of submerged glaciers causing an acceleration of ice discharge. Intruding warm deep water also melts the underside of floating ice shelves, which also accelerates calving and ice discharge.

Instrumental records of Greenland’s air temperatures, also recorded the fastest rate of warming during the 1930s and 40s coinciding with increased inflows of warm Atlantic water. Accordingly intruding warm waters alsotransported more southerly fish species, prompting the birth of Greenland’s Cod fishery. CO2 driven models have completely failed to simulate this Arctic warming.

Simultaneously the best studied Greenland glacier, the Jakobshavn, began retreating from its Little Ice Age maximum with it fastest observed retreat of 500 meters per year between 1929 and 1942. The rapid retreat was amplified when the glacier’s terminal front became ungrounded from the ridge. That earlier grounding point had previously prevented warm subsurface waters from entering its fjord. With more warm water entering the fjord, the grounding point rapidly retreated.

When warm water intrusions subsided, the glacier stabilized, and even began advancing between 1985–2002. Although the recent retreat of Greenland’s glaciers is reported as an acceleration relative to the 70s, the rate of retreat is now much slower than the 30s and 40s. And again the 20th century pattern of retreat does not correlate with rising CO2 concentrations.

Warm Water Flow into the Irminger Current

The 20th century pattern of Greenland’s melting glaciers correlates best with the timing and distribution of intruding warm Atlantic water. As seen in these illustrations, due to changes in the North Atlantic Oscillation in the 1990s, a sudden influx of warm Atlantic water entered the Irminger Current. The numbers here indicate that the current’s temperature cooled from 10°C to 1.5°C above freezing as it traveled along Greenland’s coast.

Lost Ice Mass from Grace satellite data

As seen here from recent satellite estimates, the amount of Greenland’s lost continental ice, coincides with the warmth of the Irminger Current, with pinker areas representing the highest rates of lost ice.

Warm Atlantic waters that don’t enter the Irminger Current, continue deeper into the Arctic, mostly via the Barents Sea.  Greater volumes of intruding warm water cause greater reductions of ice in the Barents and Kara Seas, deep inside the Arctic Circle. Danish Sea Ice records reveal a similar loss of sea ice during the 1930s rivaling the recent decline.

Coinciding with cycles of reduced sea ice, glaciers on the island Novaya Zemlyain the Barents Sea, also underwent their greatest retreat around 1920 to 1940.  After several decades of stability, its tidewater glaciers began retreating again around the year 2000, but at a rate five times slower than the 1930s. The recent cycle of intruding warm Atlantic water is now waning and if solar flux remains low, we should expect Arctic sea ice in the Barents and Kara seas to begin a recovery and Arctic glaciers to stabilize within the next 15 years.

The contrasting behavior of Antarctic Ice is further confirmation that intruding warm water is a natural driver of melting polar ice. Unlike ice that melted deep inside the Arctic Circle, Antarctic Sea Ice has increased to record extent and expands far outside the Antarctic Circle. Why such polar opposites? Because Antarctica is shielded from intruding warm waters by a Circumpolar Current.

Antarctica’s Circumpolar Current consists of warm subtropical waters driven eastward by westerly winds. Because there are no continents to block its path or deflect those warm waters poleward, the Circumpolar Current simply encircles the continent. The one place where Antarctic sea ice has retreated slightly, only occurs along the western side of the Antarctic Peninsula where the Circumpolar Current makes its closest approach.

Likewise without intruding warm waters, Antarctica has lost far less continental ice than Greenland. Although Antarctica contains 14 times more ice than Greenland, Greenland has lost between 2 and 5 times more ice than Antarctica. Based on changes in gravity, most areas of Antarctica have slightly gained ice designated by greenish tones. However where warm waters and winds of the Circumpolar current approach the Peninsula, there has been moderate ice loss designated by bluish tones. And despite being Antarctica’s most poleward coastline, there has been a great loss of glacier ice around the Amundsen Sea, illustrated by redder tones, causing a net loss of ice for the continent.

Antarctic Basal Melt Hot Spots 

The reason for this concentrated melting is due to the upwelling of relatively warm Circumpolar Deep Water that lurks 300 feet below the surface. Glaciers along the Amundsen Sea terminate in deep water, and are most susceptible to periodic upwelling of that warmer deep water, which causes basal melting.

Maps pinpointing regions with the greatest basal melt, highlighted here by red dots, coincide with the greatest loss of glacier ice along the Amundsen Sea hot spot. Amundsen glaciers are grounded along the coastal shelf where ancient channels can direct warm, upwelled deep water directly to the base of the glaciers. Early explorers reported excessive crevasses and concave surfaces on these glaciers suggesting extreme basal melting was happening in 1950s, and was likely a process that has been ongoing on for millennia. Much like Greenland’s  Jakobshavn glacier, once Amundsen’s glaciers retreated from their Highest ridge on the continental shelves, upwelled warm water could overflow the ridge and melt an increasingly larger cavity near the glaciers grounding points. In turn, a larger cavity allows even more warm water to enter. In contrast, the few Amundsen Sea glaciers with grounding points located beyond the reach of upwelled waters, those glaciers have not lost any ice.

Like the rhythm of retreating and advancing glaciers, rates of sea level rise have ebbed and flowed as seen in this graph from the IPCC. Again it is the 30s and 40s that experienced both the greatest retreat of glaciers and the fastest rise in global sea level. With the recent decline in solar flux and the shift to cool phases of ocean oscillations, natural climate change suggests that although glacier retreat and sea level rise will likely continue over the next few decades, the rates of sea level rise and glacier retreats will slow down.The next decade will provide the natural experiment to test the validity of competing hypotheses. Are changes in the earth’s ice  driven by natural or CO2 driven climate change. I am betting on natural climate change.   

Rates of Change in Sea Level 

Read more about natural climate change In Landscapes and Cycles: An Environmentalist’s Journey to Climate Skeptisicsm!  

Will Greenland Begin Accumulating Ice in 2015 and Beyond?

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 toVelicogna’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.”

 

Greenland ICe loss and the Warm Irminger Current

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.

Trends in Inflow of Warm Atlantic Water

 

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 2014increased 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. 

Glacier Basal Melt due to 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. 

Transport Index of  Warm Atlantic Water and North Atlantic Oscillation

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 byBengtsson (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.

Subpolar Gyre and Arctic Currents 

With all things considered, the evidence strongly suggests we will soon witness a similar natural cycle and a rebound in the Greenland’s ice.