World Meteorological Organization says sea level rise accelerating, fed by land ice melting
From the World Meteorological Organization: “The amount of ice lost annually from the Antarctic ice sheet increased at least six-fold, from 40 Gt per year in 1979-1990 to 252 Gt per year in 2009-2017.
The Greenland ice sheet has witnessed a considerable acceleration in ice loss since the turn of the millennium.
For 2015-2018, the World Glacier Monitoring Service (WGMS) reference glaciers indicates an average specific mass change of −908 mm water equivalent per year, higher than in all other five-year periods since 1950.”
The “dramatically changing landscape” of Mer de Glace
From New Scientist: “About a century ago, women with boaters and parasols sat near the Montenvers train station above the glacier, which then was almost level with a tongue of jagged ice snaking into the distance. Today, visitors are greeted by a slightly sad and largely grey glacier that is about 100 metres lower.”
An interdisciplinary analysis of changes in the high Andes
From Regional Environmental Change: “The high tropical Andes are rapidly changing due to climate change, leading to strong biotic community, ecosystem, and landscape transformations. While a wealth of glacier, water resource, and ecosystem-related research exists, an integrated perspective on the drivers and processes of glacier, landscape, and biota dynamics is currently missing. Here, we address this gap by presenting an interdisciplinary review that analyzes past, current, and potential future evidence on climate and glacier driven changes in landscape, ecosystem and biota at different spatial scales.
Our analysis indicates major twenty-first century landscape transformations with important socioecological implications which can be grouped into (i) formation of new lakes and drying of existing lakes as glaciers recede, (ii) alteration of hydrological dynamics in glacier-fed streams and high Andean wetlands, resulting in community composition changes, (iii) upward shifts of species and formation of new communities in deglaciated forefronts,(iv) potential loss of wetland ecosystems, and (v) eventual loss of alpine biota.”
The credit rating agency Moody’s announced on July 24 that it had acquired a majority stake in Four Twenty Seven, a leading provider of insight on economic climate risk. The acquisition by one of the world’s foremost credit rating agencies stands out as an indicator that the climate crisis is seen as a material risk that corporations and governments must consider.
Four Twenty Seven uses outputs from climate models to assess physical risks associated with climate-related processes for governments and companies. Heat and water stress, extreme precipitation, cyclones, and sea level rise are among the hazards Four Twenty Seven scores to quantify climate risk exposure for its clients.
Moody’s acquisition, which was widely covered in the media, indicates a responsiveness to investors who are clamoring for not just environmental, social and governance (ESG) intelligence to inform their decisions, but climate data too.
Richard Cantor is the chief credit officer at Moody’s. “Over the last few years we’ve become much more systematic and transparent about how we are incorporating ESG factors generally, and climate change in particular, into our credit rating analysis,” Cantor said, referring to the Four Twenty Seven acquisition. “This will help us do even more.”
What the acquisition of Four Twenty Seven enables the credit rating agency to do, explained Henry Shilling, a former senior vice president at Moody’s who oversaw the corporation’s ESG integration during his 25-year tenure, is to help Moody’s to make more sound financial decisions.
“It is clear to Moody’s, as well as other rating agencies, that climate risks have become elevated and they have financial and policy implications,” Shilling told GlacierHub. “It would help refine their capacity to anticipate how these risks could impact their ability to generate future cash flow, which is the primary basis for assessing credit quality.”
Reflecting their seriousness about sustainable investing, earlier this year Moody’s acquired Vigeo Eiris, a global leader in ESG research, data, and assessments. What’s become clear is that ESG is not just a values-based approach—it’s a commercial opportunity.
According to the U.S. Fourth National Climate Assessment, along the U.S. coastline, public infrastructure and $1 trillion in national wealth held in coastal real estate are threatened by rising sea levels, higher storm surges, and the ongoing increase in high tide flooding.
Bruce Usher, a professor and co-director of the Tamer Center for Social Enterprise at Columbia Business School, said Moody’s is a traditional firm and that its acquisition of Four Twenty Seven represents a significant shift in how the private sector is evaluating risk. “For them to reach the point where they believe that having a deeper understanding of [climate] risks, and presumably how those risks affect and ultimately are priced into financial assets…that’s an important signal,” he told GlacierHub. “This challenge of pricing financial risk is becoming important to the point where commercially you have to do it.”
Sea level rise is one of the physical factors forcing companies and governments examine their adaptation and mitigation strategy. Glaciers play a significant role in this process.
While glacier retreat is one of the more noticeable—and traceable—effects of the climate crisis, the impact of reduced glacier volume to business operations is not as obvious. Glaciers are referenced in several posts on Four Twenty Seven’s website, specifically on the topic of sea level rise and its effect on maritime shipping and coastal real estate. Glacier melt is occurring more rapidly than previously thought, accounting for 25-30 percent of observed sea level rise since 1961.
Seaborne shipping, which accounts for 90 percent of all global trade, is expected to be impacted by more severe storms and inundation of low lying port facilities. Anticipated effects on coastal real estate are even more worrisome.
An estimated 2.5 percent of the global population could be displaced with two meters (6.5 feet) of sea level rise, the level experts say coasts should plan for by 2100. Founder and CEO of Four Twenty Seven, Emilie Mazzacurati said real estate lies on the frontline of exposure to climate change. “Many valuable locations and markets are often coastal or near bodies of water, and therefore are going to experience increases in flood occurrences due to increases in extreme rainfall and to sea level rise,” she said in a 2018 company press release.
“These risks can now be assessed with great precision—the availability of this data provides investors with an opportunity to perform comprehensive due diligence which reflects all dimensions of emerging risks,” Mazzacurati added.
Her Berkeley, California-based company holds detailed climate risk data covering over 2,000 listed companies, one million global corporate facilities, 320 real estate investment trusts, 3,000 US counties, and 196 countries.
The name Four Twenty Seven is an homage to California’s calculated 1990 total emissions inventory: 427 million metric tons of carbon dioxide. The figure became the target to reduce emissions by 2020, which the state achieved four years early. It is worth noting that California’s economy grew by 26 percent during the period in which it reduced its emissions.
Natalie Ambrosio, who manages publications and communications at Four Twenty Seven, says companies and governments are awakening to the need for their services. “They’re increasingly aware that sea level rise and the rippling impacts of sea level rise are going to affect them directly on their own assets and also indirectly through impacts on infrastructure,” Ambrosio told GlacierHub. “We’re seeing more of our clients coming to us wanting assessments on their exposure to these impacts.”
The tricky part is how to price risks with the time horizons associated with climate disruption, which often lie far in the future.
Usher explained the dilemma facing risk managers. “The challenge at the intersection of climate risk and the financial markets is understanding how risk affects the value of assets today when climate risk is primarily considered a long-term risk with significant uncertainty,” he told GlacierHub. “It is very difficult for owners of financial assets to price those risks given those time frames and those uncertainties.”
Intelligence from a climate risk provider like Four Twenty Seven can help.
Regulatory initiatives toward low carbon economies across much of the world are also prodding rating agencies, like Moody’s, toward an embrace of climate risk intelligence.
Those in the field of evaluating climate risk say the time is already overdue for companies and governments to start addressing adaptation and mitigation risks. “Is the world sleepwalking into a crisis?” the World Economic Forum’s 2019 Global Risks Report begins. “Global risks are intensifying but the collective will to tackle them appears to be lacking.”
A new study published April 8 in the journal Nature found that glacier melt is occurring more rapidly than previously thought and accounts for 25-30 percent of observed sea level rise since 1961. The research used a new approach to produce more precise and accurate measurements, improving upon previous studies of glacier contribution to sea level rise.
The international research team, based at the World Glacier Monitoring Service at the University of Zurich, says glaciers lost more than 9,000 billion tons of ice since 1961, raising ocean levels by 27 millimeters. The team used field observations and satellite measurements from over 19,000 glaciers to reconstruct changes in ice thickness.
The study’s principal author, Michael Zemp, leads the World Glacier Monitoring Service and is involved with various scientific projects in the Department of Geography of the University of Zurich. “Glaciological measurements made in the field provide the annual fluctuations, while the satellite data allows us to determine overall ice loss over several years or decades.” Zemp said in a press release from the University of Zurich. “By combining these two measurement methods and having the new comprehensive dataset, we can estimate how much ice has been lost each year in all mountain regions since the 1960s.”
Glaciers in Alaska were the largest contributors, followed by melting ice fields in Patagonia and Arctic glaciers. Glaciers in different parts of the world make their contributions to sea level rise in different decades. A glacier’s input to sea level rise is determined by their mass and rate of loss. Alaskan and Patagonian glaciers, for example, are not as far poleward as some other glaciated regions. They are melting faster and contributing the most to sea level rise due to their large glacier area. Conversely, Antarctica’s periphery glaciers, situated near the south pole, contributed least to sea level rise during the study period. While glaciers in the western US, Canada, and Iceland, located in even warmer climates than Alaska, lost the most mass. Due to their small total glacier area of those regions, however, they contributed little to sea level rise.
Sea level rise is a direct result of climate change, though its local and regional extent and impact varies, and depends on geologic, oceanographic, and atmospheric influence. The primary contributors to ocean volume and mass are from thermal expansion (water expands as it warms) and the addition of melt water from ice sheets and glaciers. Glaciers are made up of fallen snow that, over many years, compresses into large, thickened ice masses, and due to their mass, flow like very slow rivers. As they melt, their runoff contributes to sea level rise. Ice sheets, which cover most of Greenland and Antarctica, are a mass of glacial land ice extending more than 50,000 square kilometers (20,000 square miles), whose meltwater raises sea levels. An ice shelfis a portion of an ice sheet that spreads out over water. Because ice shelves are already on the water, they do not contribute to sea level rise as they melt.
Understanding the physical processes behind glacier mass loss and its effect on sea level rise is crucial to projecting the impacts of climate change for society. According to the Fourth National Climate Assessment, a congressionally mandated report issued by the US Global Change Research Program, sea level rise this century and beyond will pose a growing challenge to coastal communities, infrastructure, and ecosystems from increased (permanent) inundation, more frequent and extreme coastal flooding, erosion of coastal landforms, and saltwater intrusion within coastal rivers and aquifers. Glaciers are not just icons of climate change; their rate of retreat is an indicator of warming and accurate accounting of their melt is necessary for calibrating models of sea level rise.
Zemp and his colleagues aimed to use updated methods to provide a clearer view of the extent of global glacier loss. “Over 30 years suddenly almost all regions started losing mass at the same time,” said Zemp. “That’s clearly climate change if you look at the global picture.”
The most significant improvement from the Intergovernmental Panel on Climate Change’s Fifth Assessment Report (IPCC AR5) in 2013, according to the authors, is the volume and accuracy of remote sensing data. Sampling increased from a few hundred glaciersto more than 19,000 globally, with an observational coverage exceeding 45 percent of the glacier area in 11 out of 19 glacier regions. Studies included in that report had to rely on data from 2003–2009, while earlier years had to be estimated. IPCC AR5 documented the sea level contribution of all glaciers globally to be 0.71 millimeters per year. Zemp’s study found that glaciers contribute 18 percent more than was reported in IPCC AR5, around one millimeter of sea level rise per year.
Matthias Huss, a Swiss glaciologist from the University of Fribourg and Secretary for Glaciers at the Cryospheric Sciences of the European Geosciences Union, was also involved in the study. Huss told GlacierHub, “In comparison to the knowledge included in the last assessment report of the IPCC the increase in remotely-sensed information on glacier mass change is tremendous.” He added, “our study has now attempted to combine all data, also including development of new approaches for optimally combining the available measurements.”
Recent advances in remote sensing and computational power have allowed scientists to overcome a stubborn obstacle, which limited their ability to calculate the total volume of glacier ice in the world. Since satellites look down on the world’s glaciers, total area is simpler to measure. But to estimate volume, it is necessary to know how thick glaciers are. As climate change progresses, ice thickness data can help researchers develop more accurate estimates of global glacier volume, and in turn, regional freshwater reserves and potential contribution to sea-level rise.
Producing accurate ice-thickness estimates, however, has proven difficult. In the absence of direct measurements for most of the world’s glaciers, previous studies primarily relied on models built from thickness estimates obtained by using ice-penetrating radar. These show that glaciers that are larger in area also tend to be thicker.
In a recent study in Nature Geoscience, researchers used, for the first time, a five-model ensemble to measure the ice thickness distribution of the world’s 215,000 glaciers, excluding the Greenland and Antarctic ice sheets. They estimated the total global glacier volume at 158,000km2. When broken down by region, they found that High Mountain Asia (HMA), comprised of the Tibetan Plateau and neighboring mountain ranges, has 27 percent less ice than previously thought and could lose at least half of its glacier area by the mid 2060s.
“In light of the importance of glacier melt for regional water supply, these differences are unsettling,” remarked the researchers in the study.
Much as a traffic helicopter can measure the speed of cars by comparing photos taken over intervals, which allow them to trace individual cars, recent satellite imagery allows scientists to observe specific features on the surface of glaciers as they progress downslope. Researchers used the Randolph Glacier Inventory (RGI) 6.0, which contains surface topography information for 215,000 glaciers. Then, they employed principles of surface ice flow dynamics—for example, thicker ice moves faster, and ice overall moves faster when the slope of a mountain is steeper—to obtain estimates of ice thickness.
This study builds on the results of an earlier version published in 2012, that was “mainly born out of the realization that wow, up to that stage, there was no estimate for the global glacier ice thickness distribution available at all,” Daniel Farinotti, a glaciologist at the Swiss Federal Institute of Technology in Zurich told GlacierHub. The 2012 study also used the RGI 2.0, which counted 26 percent less total glaciers, and calculated ice thickness estimates based on just one model.
The 2019 study’s volume estimate was just 7 percent less than in 2012, a gap mainly attributable to model differences. That said, the regional distribution of glacier ice volume in 2019 was much different, measuring a 24 percent increase in the Antarctic periphery, which was offset by decreases in the Arctic, the southern Andes, and the 27 percent decrease in HMA.
Matthias Huss, a glaciologist at the Swiss Federal Institute of Technology in Zurich and University of Fribourg, described to GlacierHub one way the 2019 study improved upon the results in 2012. “Whereas the 2012 study was ONE (the first) model for global glacier ice thickness distribution, in the present study FIVE different models were applied, developed by different research groups and with partly different underlying parameterizations,” he said. “This allows providing a “consensus” estimate, and to narrow down uncertainties.”
Both Farinotti and Huss agreed that the RGI 6.0, coupled with better satellite imagery, also made major contributions to the 2019 estimates, especially considering the significant differences between regions. Farinotti explained to GlacierHub how the improved RGI 6.0 could impact these estimates. “If a large glacier is split into two or more parts, the estimate thickness is significantly smaller,” he said. Farinotti also provided a concrete example, explaining that two glaciers each with an area of 10km2 would have significantly less ice volume than one glacier with a 20km2 area.
This study offers important findings to the hundreds of millions of people in High Mountain Asia that depend on glacier runoff as a source of freshwater. Based on the 2012 study, glacier area in HMA was likely halve by the end of the 2070s, but the new study moves this estimate up more than a decade, to the mid 2060s.
Glaciers “Knowing how thick [glaciers] are is equivalent of knowing how much cash we have in a bank account,” said Farinotti. According to this study, water reserves in High Mountain Asia are much smaller than previously believed. This could have significant impacts on how planning for future water use might take place, and highlights the importance of mitigation measures in response to rapid global climate change.
From Proceedings of the National Academy of Sciences: Antarctica’s ice is melting at an accelerating pace—six times the melt rate four decades ago—and that could have significant consequences for coastal communities around the world. The Antarctic shed 40 billion tons of ice each year between 1979 and 1989. But researchers say that the southern continent has been shedding 252 billion tons of ice each year since 2009.
“I don’t want to be alarmist,” Eric Rignot, an Earth systems scientist for both the University of California, Irvine, and NASA, who led the work, toldThe Washington Post. “The places undergoing changes in Antarctica are not limited to just a couple places,” said Rignot. “They seem to be more extensive than what we thought. That, to me, seems to be reason for concern.”
From Inspiring Girls Expeditions: Offering free, wilderness excursions for high school-aged girls, Inspiring Girls Expeditions aims to foster curiosity about the natural world and methods of scientific inquiry. Since 1999 University of Alaska, Fairbanks glaciologist Erin Pettit has led over a dozen “Girls on Ice” trips to Washington’s South Cascade Glacier.
Pettit founded the program because “I wanted to share the inspiration, curiosity, and excitement of using science to learn and explore the mountains. In turn, the girls have taught me about the dreams, and challenges, and amazing variation of lives and experiences for girls from all different communities and cultures across the world.”
Upcoming Girls on Ice expeditions include trips to the Gulkana Glacier in Alaska, Washington’s Mount Baker, the Asulkan Valley in British Columbia, and the Findelen Glacier in Switzerland.
Find out more about Inspiring Girls Expeditions here.
A New Tool for Modeling Glacier Flow
From The Journal of Chemical Physics: Bo Persson, a theoretical physicist at the Jülich Research Center in Germany, has developed an improved model of glacier flow. Persson said his model improves understanding of the cavities that form between ice and bedrock and how water fills these cavities and becomes pressurized.
Persson’s past work has focused on rubber friction and adhesion. “I could take knowledge I have gained during maybe 10 or 15 years of studies of other friction and quickly apply it to the glacier friction problem,” he told the CBC.
The model could help improve estimates of how much glacier melt is contributing to sea level rise around the world.
In this week’s Video of the Week, watch a massive glacier calving event that occurred at Helheim Glacier in Greenland. The video was captured on 22 June 2018 by Denise Holland of New York University.
The calving event took place over a 30-minute time period, and was sped up into a time-lapse of about 90 seconds. During this time span, over four miles of the glacier’s edge broke off, flowing into one of the fjords that connects Helheim Glacier to the ocean. To put this in perspective, a calving event of this size would measure roughly the size of lower Manhattan, all the way to Midtown in New York City. In a warming world, glacier calving is a large force contributing to global sea-level rise.
The GlacierHub News Report is a bi-monthly video news report that features some of our website’s top stories. This week, GlacierHub news is covering glacier flow, glacier calving, and the environmental monitoring of Svalbard and Jan Mayen.
This week’s news report features:
Observing Glacier Calving through Time-Lapse Imagery and Surface Water Waves
By: Sabrina Ho Yen Yin
A recent paper published in the Journal of Glaciology explores how a team of researchers studied waves in a Patagonian lake to detect glacier calving events at Glaciar Perito Moreno.
Summary: A new analysis published in the Journal of Science argues that the “largest uncertainty” in ice sheet models used to predict future sea-level rise originates from our limited understanding of underwater processes at the ice-bed interface.
The Environmental Monitoring of Svalbard and Jan Mayen
By: Sabrina Ho Yen Yin
Summary: The Environmental Monitoring of Svalbard and Jan Mayen (MOSJ) is an umbrella program that collects and analyzes environmental data in the arctic regions of Svalbard and Jan Mayen. Some data of interest include the extent and thickness of sea ice around Svalbard, Fram Strait and the Barents Sea; temperature and salinity of the water transported around Svalbard via the West Spitsbergen Current; ocean acidification; and local sea level changes.
For the 40 percent of the world’s population who live within 100 kilometers of the coastline, sea-level rise is more than just a mathematical calculation, it’s a survival challenge. Although scientists are confident about the impacts of accelerated glacier melting and ice flow on rising sea levels, projections for future ice loss remain at a fairly early stage. Developing better predictions for how glaciers melt and flow in the future remains a daunting task for glacier modelers.
A new analysis published in the Journal of Science argues that the “largest uncertainty” in ice sheet models used to predict future sea-level rise originates from our limited understanding of underwater processes at the ice-bed interface. These ice-bed processes beneath water involve interactions among the weight of the ice, water pressure, and the roughness of the bedrock. One of the major consequences, of these underwater interactions and a cause of sea-level rise is basal sliding, when the glacier slides over the bed as a result of meltwater between the ice and the bed acting as a lubricant.
To address the uncertainties of ice sheet models, the paper analyzed 140 wet-based glaciers in Greenland. Wet-based glaciers are known to have a thin layer of water between the ice and the rock bed. In contrast, glaciers found in the frigid Antarctic lack such a layer and are frozen to the end.
Scientific research on glaciers began in the early 18th century and developed more fully later on. Although glaciers seem static, their waning and waxing over time has long been recognized. Several theories have been proposed for this characteristic, including the Weertman formula, named after scientist Johannes Weertman. The Weertman formula states that the speed a glacier moves at its bed beneath the water is determined by both the friction and the amount of water surrounding the bed. Withstanding some bickering between Weertman and other scientists during the 1950s, the Weertman model has been widely accepted since then. An array of sea-level rise prediction models have built on this theory, with the latest study challenging the findings of the Weertman formula.
One of the two authors of the study, Leigh Stearns, a scientist at the Center for Remote Sensing of Ice Sheets from the University of Kansas, spoke to GlacierHub about her research on the topic. “We found that the commonly-used model for basal sliding (the Weertman model) does not apply to all 140 Greenland glaciers that we analyzed,” she said.
Instead, the researchers found that subglacial water pressure, the water pressure difference between the ice sheet end and the hard bed underwater, dominates the speed of glacier flow.
Intrigued by their initial observations of the 140 overlooked mountain glaciers in Greenland, Stearns and her university colleague C. J. van der Veen found the effect of friction on glacier sliding speed to be “virtually non-existent,” which implicitly defers the Weertman notion. As a result, they spent a long time trying to figure out what other factor correlated better with glacier speed, according to Stearns.
This analysis involved a closer study on the subglacial water pressure in Greenland. Stearns and van der Veen believe this aspect has been largely overlooked by the glaciological community to date. They started their observations by calculating water pressure from the thickness of the ice and then calculating the effective pressures under the water. Stearns and van der Veen paired these findings with the latest observational data about glacier flow speed and found that the two are highly related.
From yesterday's #IceBridge flight: The complex southern shear margin of Jakobshavn Isbræ in western Greenland, with an ambiguous grounded-to-floating transition. pic.twitter.com/T3DdpYlVjJ
However, Stearns also discussed the limitations of her study with GlacierHub. “We don’t understand all the mechanics for why the relationship between sliding velocity and effective pressure are so good, and why the relationship between sliding velocity and basal drag is so bad,” she said.
Recognizing these uncertainties, the paper focused on current models of sea-level rise, which are based on the strong relationship between sliding speed and the roughness of the bed.
“Hopefully it will allow them to constrain their sea-level rise prediction models better, so uncertainties of future ice sheet mass balance are reduced,” Stearns added.
The paper notes that it is “imperative for the ice sheet modeling community to explore the impact that this new relationship may have on sea-level rise prediction.” With that said, the consequences of the researchers’ new and challenging theory are still unfolding and could be highly significant.
GlacierHub contacted other scientists who built their work on the Weertman theory for feedback on Stearns and van der Veen’s latest findings, but these scientists did not respond to GlacierHub’s request for comment.
We are proud to present our first ever GlacierHub News Report. The GlacierHub News Report is a bi-monthly video news report that features some of our website’s top stories. We know our readers are busy, so we created the GlacierHub News Report to catch you up on the latest glacier news.
This week’s news report features:
Peruvian Farmer Explains Lawsuit Against Energy Firm
By: Brian Poe Llamanzares
Peruvian Farmer Saul Lliuya prepares for the next step in his legal battle against German energy firm RWE. He knows the odds are stacked against him, but with the help of Germanwatch and research from Instituto Nacional de Investigacion en Glaciares y Ecosistemas de Montaña, he hopes to win this case.
Artist Diane Burko Shows Us Our World, and It’s Vanishing
By: Jade Payne
We interviewed Diane Burko about her newest exhibition, Vast, and Vanishing, on display at the Rowan University Art Gallery, as well as her upcoming project that takes her in a new direction exploring coral reefs.
Inequality, Climate Change, and Vulnerability in Peru
By: Angela Quevedo
In March, we published an article regarding the vulnerability of small-scale farmers in Ancash, Peru. A recent study, suggests that climate change is just one of several factors placing pressure on farmers; rather, a collection of socio-political and economic factors are the main cause of vulnerability.
Glacial Geoengineering: The Key to Slowing Sea Level Rise?
By: Andrew Angle
Could building underwater walls in front of glaciers slow down melting and possibly avert devastating sea level rise? A postdoctoral researcher at Princeton thinks it might, proposing that a wall’s construction on a glacier grounding line could limit warm water from melting the ice from below. The idea is still in its very early stages and has many engineering and feasibility questions that still need to be addressed.
The signing of the Paris Agreement in December 2015 signaled the world’s renewed focus on limiting global temperature rise to below 2 degrees Celsius, with a goal to lessen the adverse impacts of climate change. However, one of these impacts, sea-level rise, is already occurring and will continue long after emissions and temperatures stabilize. In other words, policies and decisions made now will set sea-level rise on a course to higher or lower levels. To better assess these effects, a recent paper published in Nature Communications examined the implications of the Paris Agreement’s goals on global sea levels up until the year 2300.
If we are to achieve the 2 degree Celsius goal of the Paris agreement, global greenhouse gas (GHG) emissions must peak and subsequently decline in the near future. This decline would coincide with the removal of emissions already in the atmosphere, through natural sinks, carbon capture and storage technologies, or both; ultimately leading to global net-zero GHG emissions sometime between 2050 and 2100. Most previous studies examining sea-level rise under different climate change scenarios only looked forward to 2100, and though a few extended farther into the future, none had yet to consider the implications of meeting the aims of the Paris Agreement.
The goal of this study was to fill this gap and assess the legacy of the Paris Agreement on sea level rise beyond the 21st century, author Alexander Nauels told GlacierHub. Another important motivation for the study was to investigate the effect of delayed climate mitigation action on future sea-level rise, he added.
Sea-level rise due to climate change is driven by several elements, including the thermal expansion of the oceans as they warm, the retreat of mountain glaciers, and the mass loss of ice sheets in Antarctica and Greenland. These elements react on different timescales to increasing temperatures ranging from hundreds (shallow water thermal expansion and glaciers) to thousands (major ice sheets) of years. Thus, emissions today will lock in future sea-level rise well into the future.
To explore the relationship between the provisions of the Paris Agreement and sea-level rise, the study utilized a carbon cycle and climate model composite, together with a sea-level model. These models were driven by fossil fuel and industry emission scenarios that meet the Paris Agreement’s goal of limiting temperature rise to 2° C. These scenarios resemble the IPCC’s Representative Concentration Pathways (RCP) 2.6 scenario where emissions peak by 2020 and then decline thereafter. The emissions in these scenarios were limited to fossil fuels and industry because as Nauels states they are, “…by far the most important emission share when it comes to global decarbonistion.”
The scenarios chosen met either the net-zero GHG emissions goal of the Paris Agreement, seeing a gradual temperature decline over time due to GHG removal by carbon sinks, or a net-zero CO2 goal that would only limit temperature rise to 2° C. Why the two different scenario groups? Joeri Rogelj, another author of the study, told GlacierHub that they wanted to be able to distinguish between scenarios that only stabilize warming, partially meeting the Paris Agreement’s targets (net-zero CO2) and ones that fully comply with the Paris Agreement’s targets (net-zero GHG). This distinction enabled the authors to analyze the effect that delayed or insufficient mitigation action would have on sea-level rise.
There was a stark difference between the more stringent requirements of the Paris Agreement, slowly decreasing temperature through carbon sinks and action that would only stop temperature rise at 2° C. Under net-zero GHG scenarios, median sea-level rise was 73-123 cm, while under net-zero CO2 scenarios the median rise was a much higher level at 116-164 cm. Sea-level rise also continues through 2300 in all scenarios, emphasizing the need for immediate mitigation action, although, the rate begins to slow soon after emissions peak at 0.06-0.7 cm and 0.33-0.49 cm per year for the net-zero GHG and net-zero CO2 scenarios, respectively. Ominously, under net-zero CO2 scenarios, results showed that the possibility of sea-level rise of up to 5 m by 2300 was within the 90% confidence interval.
What happens if humanity only stabilizes temperatures instead of meeting the goals of the Paris Agreement? When the authors compared the net-zero GHG and net-zero CO2 scenario groups, they found that median sea-level rise was 40 cm higher for the net-zero CO2 scenario. Another relevant factor for 2300 sea-level rise is the timing of the emissions peak. If the peak in global emissions is delayed by five years, an additional 20 cm of rise was found to occur in 2300 and when based on the 95th percentile the rise is an additional 1 m.
There is a good chance that global temperatures will increase by more than 1.5° C at least temporarily, with a 2017 study putting the chances of staying below a higher threshold of 2° C at 5%. The authors assessed this possible ‘temperature overshoot’ and found for every 10-year period where temperature rise is greater than 1.5° C a 4 cm increase in median sea-levels is expected. Overall, if global temperatures top 1.5° C no scenario showed median sea-level rise less than 1.2 m by 2300.
Lastly, the authors examined the connections between sea-level rise and the Paris Agreement’s Nationally Determined Contributions (NDC), the emission reduction goals of individual countries. If implemented in full, the NDCs would lead to a median sea-level rise between 1.45 and 1.64 meters under the net-zero CO2 scenarios and a median sea-level between 1.05 and 1.23 meters under the net-zero GHG scenarios. 95th percentile estimates for the NDCs were even more dramatic, with net-zero CO2 and net-zero GHG sea-level rises between 4.1 to 4.8 m and 2.3 to 3 m respectively.
Further research is needed to develop more precise estimates of sea-level rise into the future, according to Rogelj. He proposes several concrete steps inculding better continuous observations and improved model development for Antarctic ice sheet instabilities and Greenland ice discharge, both of which contributed the most to this study’s uncertainty ranges.
The findings of this study point to continued sea-level rise up until 2300, even if global GHG emissions reach net-zero levels. However, the authors note that high-end scenarios “can be halved through early and stringent emission reductions,” highlighting the urgent need for fast action on climate change from individuals all the way up to the world’s biggest countries.
Researchers have generally thought that the East Antarctic Ice sheet has remained relatively stable despite global warming. But this is not the case, according to a recent study published in Science Advances. Chad Greene and a team of researchers discovered that the Totten, the largest glacier in East Antarctica, is melting. Shockingly, if the Totten Glacier were to melt entirely, it could raise sea levels by 11 feet.
“For the past decade, my research group at the University of Texas Institute for Geophysics has flown airborne campaigns over Totten to characterize its sensitivities, because Totten drains a massive portion of the East Antarctic Ice Sheet, about 550,000 km2, or ~3.5 m sea level rise in a complete collapse scenario,” Greene told Glacierhub. “That’s about as much ice as all the rapidly-changing glaciers of West Antarctica combined.”
The team’s project to study the Totten was a collaboration between the University of Texas at Austin, the University of Tasmania, and the Antarctic Climate and Ecosystems Cooperative Research Centre. Fernando Paolo, another member of the team, has shown that for long-term observations, Totten clearly thickens and thins on an interannual basis. So, the outstanding question was, what causes these interannual changes? What force is powerful enough to affect this massive system?
Using satellite data from 2001 to 2006, the researchers noted the increased movement of the Totten Ice Shelf toward the ocean. The ice shelf represents the floating portion of the glacier. In a pervious interview, Greene describes this phenomenon as “pancake batter that’s piled up and spreads toward the edges under its own weight.” Melting, whether from the surface or the bottom in contact with the ocean, tends to thin the ice sheet and increase the rate of flow outward.
This increased melt is also confirmed by the International Collaboration for Exploration of the Cryosphere through Aerogeophysical Profiling (ICECAP) Project, a collaboration between U.S., British and Australian Antarctic researchers that has been mapping the East Antarctic ice sheet. They have identified an area near Totten Glacier that is thinning with lowering surface heights at a rate of approximately 2m per year.
“Many forces act on Totten. We used satellite images to track Totten’s movements and found that on the interannual timescale, variability in glacier speed is influenced primarily by winds over the ocean nearby,” Greene told Glacierhub. When winds over the Southern Ocean intensify, warm water is pulled up from the deep ocean onto the continental shelf, creating the hot spot. “It’s like when you blow across a hot bowl of soup and little bits of noodles from the bottom begin to swirl around and rise to the top,” he added. This comparison suggests the dynamic nature of the thermocline, which refers to the region under water where temperature changes more rapidly with depth. The wind-driven upwelling raises the thermocline on the continental shelf and dunks the underside of Totten Ice Shelf in a warm water bath.
The wind drives the thermocline, bringing warm water toward the coast of the Totten Glacier, and circulates below through submarine canyons, causing it to melt from below. “The temperature difference experienced by a parcel of ice that’s suddenly exposed to this warm water is only a couple of degrees Celsius, but remember that bit of ice may be more accustomed to water that’s just 0.2 degrees above freezing–so a 2 degrees shock is about a 10 fold increase in melting power,” Greene said. This kickstarts a positive feedback mechanism that is self-reinforcing. More inland ice is exposed to the warm waters when the coastal layers of ice melt, and when these landlocked ice drain into the ocean, sea-level rise is certain.
Greene thinks of the Totten Glacier as “the sleeping giant because it’s huge and has been seen as insensitive to changes in its environment.” However, his team’s findings have shed light on what has caused the Totten’s rates of melting to vary over the years. With climate change expected to intensify the winds over the Southern Ocean in the next 100 years, the Totten Glacier will likely be impacted. This is groundbreaking news, since people often relate melting glaciers to increases in air or ocean temperatures, when, in fact, winds are actually sufficient.
“Some basal melt is a healthy part of a steady-state mass balance for Totten, so observations of melt are not shocking or cause for alarm,” Greene told GlacierHub. However, he added that his team showed an interesting sensitivity that changes in wind over the ocean get transmitted to the ice sheet. Greenhouse gases such as carbon dioxide have amplifying effects on Antarctic winds, deciding the fate of glaciers just by deciding the movement of warm water. “Of course, that has a gloom-and-doom component, but it’s also an interesting scientific curiosity–now we see how CO2 can lead to sea level rise without warming up the air and melting ice from above, and without even warming up the ocean, but just by moving heat around within the ocean,” he said.
What is the melting of just another glacier? If it is the Totten Glacier, it could mean another 11 feet of sea level increase.
From Huffpost Green: “A new study published in the journal Nature is drawing attention to the effect of warming water on the world’s largest ice mass, Totten Glacier in East Antarctica. Melting of the glacier, which has an ice catchment area bigger than California, could lift oceans at least two meters (6.56 feet). According to researchers who mapped the shape of the ice sheet as well as the thickness of rocks and sediments beneath it to examine the historical characteristic of erosion of Totten’s advances and retreats, unabated climate change could cause the glacier to enter an irreversible and rapid retreat within the next century.”
From Zee Media Bureau: “New Delhi: NASA’s IceBridge, an airborne survey of polar ice, recently captured this stunning view of fjord of Violin Glacier, with Nord Glacier at the upper left corner. IceBridge took this image on May 16, 2016 as the aircraft crossed Greenland to fly central glacier flowlines in the east-central region of the country. This year marks IceBridge’s eighth spring campaign of science flights over Arctic sea and land.”