Listing the Bearded Seal as Threatened: A Disturbing Victory for Untestable Hypotheses and Flawed Models

Bearded Seal on typical small ice floe

I’m a longtime supporter of the Endangered Species Act (ESA). When properly abided by, it seeks to prevent extinctions and requires humanity to seek a win-win scenario where both humans and all the other species can thrive. Unfortunately, some organizations like the Center for Biological Diversity have weaponized the ESA in order to manipulate the debate on energy policy and climate change by petitioning the courts to designate perfectly robust species as endangered or threatened from future climate change. Such abuse has understandably caused a growing backlash that ultimately threatens the ESA’s original mission. The listing of the polar bear is a case in point. Despite Center for Biological Diversity assertions that “Arctic sea ice melt is a disaster for the polar bears”, research shows polar bear populations have continued to thrive and increase.

The Center for Biological Diversity also petitioned to list thriving populations of Bearded Seals as threatened or endangered by melting sea ice. In response to their petition, the National Marine Fisheries Service (NMFS) assembled a Bearded Seal Biological Review Team (BRT). The BRT’s report can be read here. Oddly, despite promoting a threatened designation, the BRT reports Bearded Seals have existed for over 1-2 million years, surviving far greater bouts of climate change as the earth bounced between several ice ages and warmer interglacials.

On average, every hundred thousand years for the past half million years, the earth has descended into an ice age. Ice accumulation on land lowered sea level by about 400 feet (120 meters). The Arctic’s presently bountiful shallow seas were left high and dry and passage from the Pacific Ocean to the Arctic Ocean was completely blocked by the resultant Beringia land bridge. Any seals trapped in a frozen Arctic were likely extirpated. During the last ice age, seals also experienced far more rapid changes than they are experiencing now or that are predicted in the future. Despite the extreme cold of the last ice age, the BRT reported “more than 20 so‐called Dansgaard‐Oeschger oscillations have been documented … each with rapid warming to near inter‐glacial temperatures over just a few decades.” 

Melting ice during our recent interglacial, known as the Holocene, has been good for seals. Sea levels rose and flooded coastal areas to create what is now the seal’s prime shallow-water habitat. Our best scientific data has determined Arctic temperatures between 9,000 and 6,000 years ago were a few degrees warmer than today, eliminating remnant glaciers and minimizing Arctic sea ice. Sea levels peaked around 6000 years ago, allowing an increased flow of warm, nutrient-rich “Pacific Water” across the shallow Bering Strait into the western Arctic. Our best scientific evidence reveals periodic warm water inflows coincide with peak marine productivity.

Unaffected by a slight increase in CO2 concentrations, sea levels began to fall as glaciers began to expand over the past 5000 years, the Neoglacial. Glaciers reached their greatest extent during the Little Ice Age 150 years ago. During the Neoglacial, average Pacific Water inflows subsided, average sea ice has increased, and marine productivity decreased. During this cooling trend, there were several warm spikes, usually associated with life-enhancing inflows of both warm Pacific and Atlantic water. High inflows consistently correlate with reduced sea ice and greater marine productivity. If the hypothesized warming from greenhouse gases proves to be true and if it can prevent further descent into another ice age or another little Ice Age, it is more likely than not such a warming effect would benefit the entire Arctic food web that sustains “threatened” bearded seals.

The state of Alaska and the Alaskan Oil and Gas Association correctly challenged the “threatened” designation as an “arbitrary, capricious abuse of discretion, or otherwise not in accordance with law”. A district court agreed concluding that the listing indeed violated the Administrative Procedure Act. In that decision, the court reported it was troubling that the Beringia population of bearded seals was listed as threatened simply based on threats predicted by climate models that would not manifest until the end of the 21st century. However, that ruling was quickly appealed and now reversed, as the courts upheld the “threatened” designation.

The judge wrote the court was required to “defer to the agency’s [NMFS] interpretation of complex scientific data so long as the agency provides a reasonable explanation for adopting its approach.” The court also ruled that the ESA requirement for proving an imminent threat in the “foreseeable future” only required a scenario that it was “more likely than not” seals could be endangered.

The court ruling maintained that “as long as the agency states a rational connection between the facts found and the decision made [for listing] it must be upheld.”  Unfortunately judges who decide the validity of a Center for Biological Diversity claim, rarely have any background in biology or climate science. Those judges must rely on what lawyers assert are “the best available scientific data”. But lawyers and advocacy scientists only present the “best available scientific data” that supports their arguments, and ignore equally valid scientific data that contradict their claims. Unfortunately all the known facts were not presented. So even though 2 million years of climate history illustrated bearded seals are highly resilient, the court was swayed by a limited selection of models and untestable predictions. So, as Paul Harvey would say, here’s the rest of the story.

Defining Sea Ice as Critical Habitat

Although the Biological Review Team acknowledged “there is ample evidence that bearded seals have

adapted successfully many times to both large and rapid ecological changes” they argued “history is not, on its own, an assurance that bearded seals can adapt to the changes projected for the foreseeable future.” To make the case bearded seals were threatened, the BRT argued sea ice is a critical habitat required for birthing, nursing, molting and for resting while over prime foraging habitat. Because global climate models predict critical sea ice habitat will disappear as CO2 concentrations rise, they argue the seals are ultimately endangered. However ample evidence suggests sea ice is not a survival requirement.

When Bearded Seals do haul out onto sea ice, they prefer tiny floes of thin first-year ice. Climate change, whether natural or anthropogenic, will not eliminate that first-year ice. As the BRT reported, “sea ice will always persist from late fall through mid‐summer due to cold and dark winter conditions.”  Much of the Bearded Seal’s habitat encompasses seasonal ice zones where first-year sea ice is renewed every winter but melts completely every summer. The Bering Sea, Barents Sea, Baffin Bay, the Sea of Okhotsk, and Hudson Bay are all seasonal ice zones. Renewed winter ice reaches its maximum in late March about the time of the solar equinox. Simultaneously whelping (giving birth) begins in March and peaks in April followed by 2 to 3 weeks of nursing, a time with plenty of ice. The loss of thick multi-year ice over the deep Arctic basin in September has no effect on bearded seals survival.

Heavy sea ice is a bigger threat to bearded seals, so they avoid regions where sea ice cover is more than 90%. Heavy sea ice acts as a barrier that prevents access to their feeding grounds. Each winter bearded seals in the Pacific sector migrate southward as winter ice prevents access to their favored feeding grounds. As sea ice recedes with increasing spring and summer insolation, feeding grounds once again become available. Bearded seals are in competition with other benthic (sea floor) feeders, walrus and gray whales, who likewise migrate into the Arctic as the ice melts. Due to the advantage of accessing the sea floor as soon as dwindling sea ice permits, bearded seals are frequently associated with 70 to 90% sea ice concentrations. Although resting on floating ice above their feeding grounds imparts a small energetic benefit, it is not a life-saving requirement.

For example, although the sample size has been very small, studies of radio-collared seals in the Bering and Chukchi Seas observed those seals rarely hauled out at all, on land or sea ice, even when occupying ice covered areas. The BRT concluded that “at least in the Bering and Chukchi Seas, bearded seals may not require the presence sea ice for a significant part of the year”.

The BRT then manufactured an untested sea-ice threshold based solely on circumstantial evidence to assert whelping and nursing required sea ice concentrations over 25%. As the BRT stated, “Research suggests that, during the time of whelping and nursing, bearded seals prefer areas where the percent concentration of sea ice is >25%. Lacking a more direct measure of the relationship between bearded seal vital rates and ice coverage, the BRT assumed that this preference relationship reflects the species requirements for sea‐ice coverage.” Based Solely on that assumption wherever climate models projected ice falling below 25% concentration, they deemed it “inadequate for whelping and nursing.” [all emphasis mine]

But breeding seals’ ice association is not a matter of preference or a requirement!  To maximize the time spent over accessible foraging grounds, pups are born in the spring when winter sea ice begins its retreat. As the BRT reported, bearded seals prefer foraging in open ice cover where the sea floor is less tan 100 meters deep. Thus, to whelp in April and still remain for over shallow feeding grounds, seals are coincidentally surrounded by extensive winter sea ice. Figure 1 below illustrates the Pacific sector’s potential foraging grounds. White regions mark shallow areas, typically 50 to 100 meters depth. Because bearded seals cannot forage in deep waters (illustrated by the dark blue color), they cannot breed in ice free waters located south of the shallow Bering Sea.

The illustration’s colored lines represent the “ice front” position each month. In March, sea ice concentrations less than 15% are found to the south of the light green line. By peak whelping time in April, heavy sea ice concentrations (turquoise line) largely remain as in March. Thus, during the optimal season for whelping, 99% of their foraging habitat is covered by ice concentrations greater than 15% and as high as 100%. Seals do not prefer to breed in this heavy ice! They are forced to if they want access to required shallow feeding grounds. Consistent with this analysis, the BRT reports during the spring in the eastern and northern Bering Sea, the Chukchi Sea, and the Laptev Sea, where much of the first-year sea ice is heavily compacted, breeding bearded seals are not found in any significant numbers.

 

Figure 1. Monthly location of west Arctic ice front

On the other hand, bearded seals are definitely adapted to survive in ice free waters. Mating always happens in the water. Native Arctic hunters observe seals giving birth in the water. Furthermore, bearded seal pups are well adapted to enter the water immediately after birth. Harp Seals for example require weeks of development on the ice. To thermo-regulate harp seal pups are born with a white fur called the lanugo. The lanugo provides excellent protection from cold air, which is why baby Harp seals were heavily hunted for the fur trade. But the lanugo provides little insulation when wet. So after a few weeks, Harp seals molt their lanugo and gain a protective layer of fat so they can enter the sea. In contrast, most Bearded Seal pups amazingly molt their lanugo within the uterus. They are also born with a thicker layer of blubber and begin foraging in the sea right after birth. So, birthing on an ice floe is more likely a convenience, but not a requirement.

Although it has not yet been reported, newborn pups are probably capable of nursing underwater as well. Based on the amount of time spent in the water right after birth this seems likely. Marine mammals such as whales and manatees must nurse underwater. And although California Sea lion pups primarily nurse on land, they too have been observed nursing underwater.

In habitat where sea ice either melts completely or recedes beyond the limits of shallow-water feeding grounds, bearded seals simply come ashore. Observations of seals on dry land have been documented for the White and Laptev Seas, the Bering, Chukchi and Beaufort Seas, for Svalbard, the Hudson Bay and the Okhotsk Sea. The Okhotsk and Kamchatka populations thrive in the most southerly part of the seal’s range where ice melts completely each summer. There, bearded seals form numerous shore rookeries comprised of tens to hundreds of individuals, during a time that overlaps with molting.

Finally, their preferred small ice floes do not offer protection from the seals’ 2 major predators. Polar bears are well adapted for surreptitiously swimming up to floating ice and snatching an unwary seal. Killer Whales readily grab a seal from floating ice or tip that ice over, dumping the seal into the water where it is no match for the Orca. Thus, many lines of evidence suggest it is “more likely than not” that observations of bearded seals resting on sea ice platforms is only evidence of a convenience, not a survival requirement.

Small ice floes do not protect bearded seals from their predators

The IPCC Models

The Biological Review Team included one climate scientist, James Overland and he predicts the Arctic will be ice free within the next decade or two. (By “ice free” he means September ice will be reduced to about 1 million square kilometers.). Although there is a general consensus among models that rising CO2 will drive warming and continued ice melt into the future, IPCC models failed to predict the current level of rapid sea ice reduction. Because IPCC models projected currently observed sea-ice reduction would not occur until 2070, Overland believes IPCC models were simply too conservative. However other evidence suggests the models are flawed because they did not accurately incorporate natural variability. Nonetheless, Overland used a select group of 6 IPCC models to convince the courts rising CO2 concentrations threatened to destroy and modify the seals’ sea ice habitat.

For the BRT analysis, Overland culled the most flawed IPCC models. His chosen models had to simulate the seasonal changes in ice cover to demonstrate an accurate sensitivity to changes in solar insolation. In addition, chosen models had to simulate (hindcast), within 20% accuracy, September sea ice extent observed from 1980 to 1999. The number of IPCC models fitting this selection criteria was reduced to six. However, the time span to accurately test the models’ reliability was far too short. IPCC models attempting to replicate 20^th century Arctic air temperatures have failed to reproduce the rapid warming from 1920 to 1940. Furthermore, those 6 models failed to accurately simulate observed sea ice extent for individual Arctic basins.

Of Overland’s 6 best models, all 6 only simulated past sea ice correctly in the Chukchi and Siberian seas. Four models correctly simulated sea ice in the eastern Bering seas.  Only one model could simulate recent sea ice in the western Bering and Barents sea. None of the models satisfactorily simulated sea ice in the Sea of Okhotsk, Hudson Bay and Baffin Bay, the Canadian Archipelago, or Greenland, Kara and Laptev Seas. As the BRT correctly cautioned, “loss of summer sea ice in the Arctic cannot be extrapolated to the seasonal ice zones which are behaving differently than the Arctic. For example, the Bering Sea has had 4 years of colder than normal winter and spring conditions from 2007‐2010, with near record sea‐ice extents, rivaling the sea ice maximum in the mid‐1970s, despite record retreats during summer in the Arctic.”

 

From Gillett 2008: IPCC models fail to simulate natural Arctic warming 1920-1940

As seen in the graph above from Gillett 2008, IPCC model simulations based solely on known natural factors (the blue line labeled NAT), erroneously reported no change in 20^th century Arctic temperatures. Observations revealed (the black line labeled OBS) temperatures had naturally oscillated. Actual temperatures compared to model results were as much as 0.6 C degrees higher in the 1930s and 40s but then lower after the 1960s. More disconcerting, when models added the effects of CO2 and aerosols to natural factors (the red line labeled ALL), discrepancies between models and 1940s observations worsened. A modeling study by Johannessen 2004 failed similarly. In contrast to flawed CO2-driven models, it is well-documented that warming from 1920-1940 as well as the current sea ice loss is more parsimoniously attributed to changes in atmospheric and ocean circulations that pump warm southerly air and water into the Arctic. Although judges believed they were presented with the “best scientific models”, those best scientific predictions had failed to simulate past natural climate change.

The BRT did not inform the courts of research that shows a small Arctic cooling trend for the period 1901 to 1997, a trend contrary to the CO2 global warming hypothesis. A similar cooling trend was reported in the 1993 paper, “Absence of Evidence for Greenhouse Warming over the Arctic Ocean in the Past 40 years”. Nor did the BRT discuss research detailing how the loss of sea ice in the 1990s was not caused by warmer air, but by a shift in the Arctic Oscillation resulting in below-freezing winds that pushed thick insulating ice out into the Atlantic.

Furthermore, it’s not obvious that the BRT advised the judges that our best scientific data has observed that past and recent reductions of sea ice have coincided with intrusions of relatively warm Atlantic and Pacific waters. Fishery data shows warming in the 1930s coincided with the arrival of fish normally found further south. Recent analyses show similar northward fish migrations are associated with intruding warm Atlantic waters, driven by natural shifts in the North Atlantic Oscillations and Atlantic Multidecadal Oscillation. In the Atlantic sector, the greatest loss of Arctic ice occurs in the Barents Sea and associated with the pathways of intruding warm water.

Intruding dense salty warm water also generates a reservoir of Arctic heat stored between 100 and 900 meters depth. That heat reservoir can melt all Arctic sea ice several times over. Indeed, the most recent scientific research reveals that warm reservoir has been rising closer to the surface and thinning sea ice. Researchers called this dynamic the atlantification of the Arctic Ocean.

In 2007, the greatest reduction of sea ice happened in the Chukchi Sea. Research by Rebecca Woodgate using mooring and satellite data, documented that the volume and heat content of intruding warm water. She reported Pacific water passing through the Bering Strait into the Chukchi had doubled since 2001. The inflowing Pacific Waters spread across half the Arctic Ocean with a heat equivalent equal to, and up to twice as great, as possible heat estimated from CO2 back-radiation. The amount of heat carried by those intruding waters was comparable to the solar heating of the entre Chukchi Sea.

The resulting enhanced loss of summer and winter sea ice resulted in feedbacks, associated with Arctic Amplification, which has raised Arctic air temperatures at a rate twice the global average. Less insulating ice allows the heat reservoir to more easily ventilate, cooling the ocean but warming the air. Furthermore, researchers show the loss of sea ice reconnects the oceans with the winds causing a stirring effect that brings warmer water to the surface. Less ice lowers the ocean’s albedo allowing more solar heat to be absorbed. Finally, the re-formation of lost ice, releases more latent heat. All those warming effects caused by increased inflows, have been myopically attributed to rising CO2.

Less ice benefits the food web. As outlined by Grebmeir 2015, the productivity in the Chukchi Sea (and likely the entire Arctic ocean) depends on the inflows of nutrient rich waters. The same intrusions of warm water through the Bering Strait that reduces sea ice, also bring vital nutrients that increases productivity, as well as bringing warmth that enhances faster growth. Our best scientific evidence suggests that if the Arctic becomes ice free by mid-21^st century, more open water will enhance photosynthesis so that marine productivity will increase by 67%. Thus, it is “more likely than not” that the dynamics that are now reducing Arctic sea ice are also increasing the food supply, not just for bearded seals but for the whole food web. Because bearded seals currently consume a huge variety of fish and invertebrates, it is highly likely bearded seals will easily adapt to any foreseeable changes in the food web.

When the “rest of the story” is told, it seems highly unlikely bearded seals will be endangered by reduced sea ice or warming temperatures. It is the Endangered Species Act itself that is endangered because the Center for Biological Diversity and their ilk abuse the ESA to promote climate fear. Instead what should rightfully evoke our greatest concern is how climate change alarmism is eroding objective science, allowing untestable hypotheses and flawed models to become codified in our legal system.

Is Antarctica’s Climate Change Natural or CO2 Driven? There Is Absolutely No Consensus

The record growth of Antarctic sea ice has long been a troubling contradiction for global warming theory. But those who embrace CO2 as the driver of climate change typically countered that global warming was still melting the continental glaciers and raising sea levels. However on October 29, 2015 a team of NASA researchers led by Jay Zwally published the paper “Mass gains of the Antarctic ice sheet exceed losses”. If the new NASA research proves correct - and there is good evidence to suggest it is - continental ice is increasing and lowering sea level. That would highlight another major failure for both CO2 driven models and models of sea level change. The reaction of Dr. Theodore Scambos, senior research scientist at the National Snow & Ice Data Center, was all too reminiscent of the “hide the decline” mentality evidenced by advocacy scientists in the climategate scandal. In an Al Jazeera interview Scambos asked, “Please don’t publicize this study.”  Others pushed back by simply listing any research that disagreed with Zwally, but rarely did they list the research supporting Zwally’s results. Nor did they delve into why there is no Antarctica consensus, as I will do here.

Some researchers did acknowledge the great climate uncertainties. Robin Bell, a research professor at Columbia University's Lamont-Doherty Earth Observatory admitted, "To me this points out that we still don't understand everything about how snow turns into ice and how the ice sheets are changing." Even more revealing were comments posted by Dr. Eric Steig at Michael Mann’s RealClimate website, comments that reveal a total lack of consensus and suggest greater support for natural climate change. Dr Steig has published extensively on Antarctica and has been a regular contributor to the RealClimate website. So he is not someone who can be dismissed as a “denier”.  Steig wrote,

“I think the evidence that the current retreat of Antarctic glaciers is owing to anthropogenic global warming is weak. The literature is mixed on this, about 50% of experts agree with me on this.”

On the other side of the issue RealClimate’s Gavin Schmidt downplayed Zwally’s results as we would expect telling interviewers, "I would pin more weight to the GRACE data than to this latest paper." But it is not a matter of putting more weight on satellite data that measures gravity change (GRACE) or satellite data that measures changes in elevation (Zwally et al).  Both methods are victimized by faulty Glacial Isostatic Adjustment models (GIA). All measurements of increased ice elevation or gravity changes are adjusted according to the assumptions of their GIA model of choice. Most GIA models assume Antarctica has been rebounding upwards since deglaciation removed the weight of glacial ice. The degree of estimated rebound depends on the region and more importantly 1) uncertain estimates of the mantle’s viscosity below the bedrock and 2) assumptions about the glacial history of Antarctica.

It is not clear if Schmidt’s advocacy for the GRACE estimates was guided by his persistent protection of the global warming meme, or if his interviewers omitted any honest discussion of papers demonstrating the upward bias in most GIA estimates. Similarly other Zwally detractors pointed to papers such as Harig 2015 that claimed Antarctica was losing ice, but Harig 2015 used GIA models that were well known to over‑estimate glacial rebound.

To remove bias in GIA models, our best method requires comparing Global Positioning System data (GPS) that measures the current bedrock uplift with GIA modeled predictions. This requires placing GPS instruments on solid bedrock, which is relatively rare throughout most of ice covered Antarctica. However along the coast wherever GPS measurements have been possible, research revealed GIA models had biased the  uplift upwards by 4.9 to 5.0 mm/years relative to GPS observations. Zwally argues that current GIA models should be lowered by just 1.6 mm/ year and that small adjustment would bring the estimates based on GRACE data into agreement with Zwally’s elevation data.

There is more evidence to support Zwallys critique of GIA models. In recent years researchers have been lowering their estimates of mass gained during the last Ice Age and lost ice mass during the recent deglaciation. Previous models estimated Antarctica deglaciation contributed 24-37 meters of sea level rise, but  that contribution has now been reduced to just 6-14 meters. This meant early GIA models had grossly overestimated the weight of past glaciers and the subsequent rebound. By adjusting the de‑glaciation history, Whitehouse 2012 revised their GIA model so that the upward bias was reduced to 1.2 mm/year with error estimates of 2.3 mm/year. Less ice also meant previous models that budgeted sources of sea level rise were wrong. Zwally’s estimate that Antarctica has been gaining ice and thus reducing sea level has created more angst that current models of sea level rise are still in need of further adjustments.

Furthermore, Zwally referenced evidence from Siegert 2003 showing parts of east Antarctica had been gaining mass for the past 10,000 years (Figure 2 below). Counter‑intuitively during the last Glacial Maximum ice accumulation dropped to a minimum. In contrast during warmer interglacials greater incursions of moisture entered the interior of Antarctica and ice accumulation peaked. Because east Antarctic is so cold (South Pole’s average summer temperature is -28C), ice ablation is minimal, so it is more likely east Antarctica is still subsiding under that weight, not uplifting. Zwally’s inference that GIA models should decrease their estimates of bedrock uplift by just 1.6 mm/year again is well supported.

Zwally questioned if snow accumulation could continue to offset the ice lost from glacier thinning elsewhere. But recent evidence suggests it will. Zwally’s study did not extended past 2008 but he estimated that during the period studied, net accumulation had reduced sea level rise 0.23 mm/year ( a 6 to 10% reduction). More recent GRACE evidence has suggested even larger accumulation events since then. A 2012 study determined east Antarctica gained 350 Gigatons of snow between 2009 and 2011, enough to decrease sea level rise by 0.32 mm/year. A 2015 study using regional ice core data reveals no unusual temperature changes but an exceptional 30% increase in snow accumulation during the twentieth century, supporting Zwally’s analysis of mass gain in interior west Antarctica.

East Antarctic Ice Accumulation between glacial and interglacial periods

Similarly Greenland’s snowfall accumulation is at all time highs and recent GRACE results show that after several years of accelerated ice loss due to glacier thinning, the net loss from Greenland in 2013-2014 was insignificant. As discussed here, relative to the years of greater ice loss in Greenland, the rate of sea level rise should have dropped by an additional 1.3 mm/year in 2014. Combining Zwally’s calculations with recent evidence from Greenland, sea level models driven by global warming should reveal a decreasing rate of sea level rise. It appears that global warming fears have been misdirecting research concerned with coastal flooding. Research shows groundwater extraction is not only contributing significantly to recent sea level rise, but land is sinking at a faster rate due to that extraction. Regretfully President Obama has highlighted coastal flooding to further politicize climate change, but never mentions the more critical issue of ground water extraction that desperately needs attention.

Zwally’s analysis also noted that previous estimates of Antarctica’s ice mass assumed that increases in elevation were due to snowfall. But when ice accumulation is greater than ice discharge, drainage basins undergo dynamic thickening, and dynamic thickening can occur in response to accumulation events that happened thousands of years ago. Because the density of ice is about 3 times the density of snow, if researchers incorrectly assume increased elevations are only due to snowfall and not dynamic thickening, estimates of ice mass will be greatly underestimated. This points out the need to see climate change within a framework of thousands of years, not just the past few decades, and Zwally’s interpretation of dynamic thickening can be readily tested by additional ice cores.

In the face of Zwally’s analysis, defenders of the CO2 warming meme retreated to stressing uncontested observations of lost ice due to dynamic glacier thinning or uncritically accepting speculative models  catastrophic deglaciation. Although Zwally calculated the net “mass gains from snow accumulation exceeded losses from ice discharge by about 112 and 82 Gt/year respectively during the 1992-2001 and 2003-08 measurement periods”, he also reported that the rate of ice loss along the west Antarctic coast and the peninsula had increased from 64 GT/year to 135 GT/year during those same periods. Alarmists seize upon this short‑term acceleration to suggest rising CO2 will cause the rate of dynamic thinning to increase. But research shows dynamic thinning has been more cyclical, intermittent and episodic with no correlation with CO2 concentrations. For example a large 1987 calving event removed 100 years of ice accumulation from the Ross Ice Shelf in just one day, an amount second only to the loss of the Larsen Ice Shelf. Such episodic events can easily be misinterpreted as an “acceleration” of ice loss. However due to the heavier snow accumulation since that time, the ice shelf has expanded further northward exceeding it previous extent in just over a decade (Keys 1998). Antarctica undergoes rapid ice loss followed by periods of slower recuperation depending on regional rates of snow accumulation. So a much broader timescale of climate change must be embraced.

Research has determined these episodic calving events are most often driven by periodic upwelling of warm Circumpolar Deep Water (CDW) that melts glaciers from below (basal melting). The extremely cold Antarctic climate maintains a 200 to 300 meter  surface layer of near freezing Winter Water that insulates warmer CDW below. All grounding points below 300 meters have been susceptible to basal melting from upwelled CDW for millennia, and a pattern has emerged that glaciers with deeper grounding points incur greater basal melting. Thus the topography of the coastal shelves and depth of submerged glacier grounding points determines the impact of upwelled CDW and limits extreme basal melting to a relatively few locations as illustrated by the red and orange areas in the figure below (from Depoorter 2013)..

Glacial Thinning and Basal Melting Hot Spots

Reports of increased basal melting due to “warmer” water is often misinterpreted to mean CDW water had been warmed by rising CO2. But CDW is a tremendous reservoir of heat that only experiences temperature changes on long‑term scales of centuries and millennia. Upwelled CDW water can be cooled when modified by winter water, or remain warm when it directly accesses a glacier grounding point. Reading recent research carefully reveals no change in the temperature CDW source waters. It is periodic increases in the volume and velocity of intruding CDW that accelerates basal melt. Coastal shelves that allow the  greatest intrusions of relatively warm CDW experience that greatest basal melt such as Pine Island and Thwaites glaciers, which account for the overwhelming majority of Antarctica’s dynamic thinning. Antarctica’s glacial thinning is a very localized phenomenon, and not evidence of global warming.

In addition to conducive topography, intrusions of warm CDW are driven by periodic changes in  the winds which in turn are controlled primarily by the Amundsen Sea Low (ASL), a quasi-permanent low pressure system. The ASL shifts poleward and equatorward, as well as eastward and westward with the seasons. It also shifts in response to inter‑annual and decadal changes in sea surface temperatures in the tropical Pacific. The shifting center of the ASL causes varying wind intensities that also alternate direction between easterlies and westerlies. As illustrated below the direction of the wind over the shelf break determines the amount of CDW that reaches the glaciers grounding points along the peninsula and Amundsen Sea. Paleo‑climate research suggests the position of the ASL also shifts between glacials and interglacials, and drove warm CDW shoreward during interglacials and accelerated glacier retreat.

Modern cycles of CDW‑driven basal melting are likewise correlated with the position of the ASL and changes in the central Pacific temperatures..  Warming of the central Pacific is associated with an El Nino variation called Modoki EL Niño (see Tisdale for further discussion). And here again there is absolutely no consensus regards the effects of CO2 on the frequency or types of El Niño, but most researchers believe El Niño is an expression of the natural climate variability.  Steig 2012 points out that a cycle warming in the central Pacific, similar to recent years, had last occurred during the 1940s. That earlier warming was associated with a large calving event of the Pine Island Glacier that likely occurred in association with an EL Nino event. Accordingly a 2013 paper reports the  “climate in West Antarctica cannot be distinguished from decadal variability that originates in the tropics.”

Wind driven upwelling of warm Circumpolar Deep Water (CDW)

Zwally deemed it necessary to acknowledge climate change fears and suggested that if the rate of dynamic thinning continues, Antarctica could begin exhibiting a net loss of ice within the next 20 years, but only if there was no compensating snowfall. Yet curiouser and curiouser neither Zwally or the researchers highlighting accelerated thinning of Amundsen Sea glaciers ever mention recent research that measured a 53% decrease in basal melting and up to a 1C drop in melt water temperatures between 2010 and 2012. Melt water temperatures that were lower under the Pine Island Glacier than 1992 temperatures. The decrease in basal melt was attributed to stronger easterly winds that encouraged downwelling along the Amundsen shelf break, which lowered the top of the thermocline (where cold winter waters meets warm CDW) and reduced the volume of upwelled  warm CDW intruding onto the shelf.  Researchers concluded that “Continuation of a deep thermocline would reverse the current ice-shelf thinning.”

Other researchers have demonstrated warming in Antarctica that followed the last glacial maximum preceded any increase in atmospheric CO2. Both warming and CO2 appear to be driven by changes in the position and strength of the westerly winds and the upwelling of warm CDW. During the past 10,000 years research at Marguerite Bay on the peninsula reveals extensive glacial melt, limited sea ice which enhanced primary productivity that lasted for over 2000 years and was consistent with evidence of increased upwelling of warm CDW. The George VI Ice Shelf collapsed about 9000 years ago but reformed 7000 years ago and that shelf still persists today. Over the last 5000 years intermittent melting and reforming of sea ice in the Marguerite Bay is consistent with enhanced sensitivity to ENSO forcing and increased upwelling of CDW; a similar sensitivity to ENSO events has been documented over the most recent decades. History strongly suggests periods of accelerated glacial thinning are natural and quite common.

A more thorough and objective  review of the peer-reviewed literature reveals an abundance of evidence supporting claims of natural climate variability that easily matches, if not outweighs, the trumpeted papers asserting CO2 driven change. It is no wonder Dr. Steig admitted ““I think the evidence that the current retreat of Antarctic glaciers is owing to anthropogenic global warming is weak. The literature is mixed on this, about 50% of experts agree with me on this.”

It will be of great interest to see how the IPCC spins this state of affairs.