Extreme Rain From Atmospheric Rivers and Ice-Heating Micro-Cracks Are Ominous New Threats to the Greenland Ice Sheet – Inside Climate News

Sustainable Development Goals (SDGs)

Goal 13: Climate Action

At the current level of human-caused global warming, extreme rainfall from atmospheric rivers, as well as an extensive network of previously undetected micro-cracks, could degrade large parts of the Greenland Ice Sheet faster than expected and accelerate melting toward worst-case projections for ice loss and sea level rise, recent research shows.

Introduction

One new study, published July 21 in Science, provides a precedent, describing a massive Greenland meltdown that happened relatively recently on the geological time scale, between about 424,000 and 374,000 years ago during a warm, interglacial period known as Marine Isotope Stage 11. That era is used as an analogue for today’s climate because temperatures in the Greenland region were about the same as now, and atmospheric carbon dioxide was about 280 parts per million, similar to the pre-fossil fuel era, but average global sea level was 20 to 40 feet higher than today.

Evidence of Thawed Region

The scientists showed that the area was ice-free at that time by measuring the luminescence signal of particles of rock and sand to determine when they were last exposed to sunlight. The deposits were at the bottom of a deep ice core drilled at Camp Century, in northwestern Greenland, more than 100 miles from the coast, just 800 miles from the North Pole and where the ice is almost a mile thick. Ice sheet modeling shows the location where the ice core was taken could have only been free of ice if other large parts of Greenland were also ice-free at the same time.

Vulnerability to Climate Change

The results are “bulletproof evidence” that the region was thawed during that warm interglacial phase, suggesting that the ice sheet is vulnerable to a moderate global temperature increase if the warming is sustained long enough, said co-author Paul Bierman, a geoscientist at the University of Vermont’s Rubenstein School of the Environment and Natural Resources and a fellow in the Gund Institute for Environment.

“What struck me in the last week, as I thought about the study and talked with people about it, is that we’re recreating at least the carbon dynamics of MIS 11 by keeping the atmosphere rich in carbon and warm for a long time,” he said. “Except we’re doing it not at 280 ppm of carbon dioxide. We’re doing it 420, soon to be 450 or 500 parts per million. So that’s a really strong forcing on the climate.”

Implications for Policy Decisions

He said that’s important when you go to the “top level idea” of the many recent ice sheet studies, summarized in a 2016 Nature Climate Change paper led by Peter Clark, which is “that policy decisions in the next 100 years will determine the next 10,000 years of climate on Earth.”

The new research “suggests a warm, wet, and largely ice-free future for planet Earth,” Bierman said. Pinpointing the timing of ice-free conditions more accurately bolsters the evidence “that Greenland is more sensitive to climate change than previously understood, and at grave risk of irreversibly melting off.”

Potential Mechanism for Ice Sheet Disintegration

Paleoclimate studies show that Earth’s ice age cycles are slow build-ups to peak glaciation over millennia, with much more sudden phases of disintegration and collapse, when the rate of sea level rise spiked to as high as 16.4 feet per century in the most extreme cases in the paleoclimate record. Current research suggests that the warming caused by greenhouse gas emissions from a handful of highly developed countries during the last century could once again trigger similar phases of extreme sea level rise in coming centuries.

The second recent study, published in June in Nature Geoscience, shows a possible new mechanism that could accelerate ice sheet disintegration. There are vast networks of previously undetected micro-cracks on the Greenland Ice Sheet that may run hundreds of meters deep, carrying warm surface water to the interior of the ice sheet and melting it from within, said David Chandler, a postdoctoral researcher at the Bjerknes Centre for Climate Research in Bergen, Norway, and a co-author.

Role of Micro-Cracks

The narrow fractures described in the paper are different from the large drainage structures often featured in dramatic climate videos from Greenland, when entire meltwater lakes pour down off the surface through holes called moulins into a deep system of tunnels that can lead all the way to the base of the ice sheet, where the water, under the weight of the ice builds up so much pressure that it hydraulically lifts the ice, enabling it to slide faster.

Chandler said he first started wondering about the significance of the smaller cracks more than 10 years ago, when he was doing field research on the ice sheet, studying how water flowed through the larger drainage structures.

“I spent a long time camping on the ice sheet and in the spring, when they open, you can hear them banging and popping and banging all the time,” he said. “It’s quite noisy, actually. I was working at four different sites where this happened in West Greenland at high elevation, where the ice is about 900 meters thick. Even there, there were cracks opening and capturing streams and developing moulins, he added.

His field work was focused on the subglacial hydrology: how and where the drainage systems develop, because that can affect the inside and the base of the ice sheet. But then he started to realize the extent of the smaller cracks, which don’t end up draining out in a big rush, and that made him wonder how the micro-cracks affect the ice from a temperature, rather than a hydrological, perspective.

Increase in Extreme Rainfall

Melting surface ice isn’t the only source of water on the Greenland Ice Sheet. Rainfall is playing an increasing role, and the amounts of rain now falling are “insane,” said Jason Box, a snow and ice climatologist at the Geological Survey of Denmark and Greenland and lead author of the third recent study, published in July by the Royal Meteorological Society documenting an increase of extreme rainstorms in Greenland.

Box said his study, the study by Chandler on the ice cracks and Bierman’s new research on Greenland’s meltdown in Marine Isotope Stage 11 “add insight to an all-too-long list of factors not yet encoded in ice sheet models used to project future sea level rise.” The increased meltwater delivery from rainfall is an important aspect of the hydrofracturing processes that are cracking up the ice sheet, he added.

SDGs, Targets, and Indicators

SDGs, Targets, and Indicators

1. SDG 13: Climate Action
• Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters
• Indicator 13.1.1: Number of deaths, missing persons, and directly affected persons attributed to disasters per 100,000 population
• Target 13.2: Integrate climate change measures into national policies, strategies, and planning
• Indicator 13.2.1: Number of countries that have communicated the strengthening of institutional, systemic, and individual capacity-building to implement adaptation, mitigation, and technology transfer
• Target 13.3: Improve education, awareness-raising, and human and institutional capacity on climate change mitigation, adaptation, impact reduction, and early warning
• Indicator 13.3.1: Number of countries that have integrated mitigation, adaptation, impact reduction, and early warning into primary, secondary, and tertiary curricula
2. SDG 14: Life Below Water
• Target 14.1: By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution
• Indicator 14.1.1: Index of coastal eutrophication and floating plastic debris density
• Target 14.3: Minimize and address the impacts of ocean acidification, including through enhanced scientific cooperation at all levels
• Indicator 14.3.1: Average marine acidity (pH) measured at agreed suite of representative sampling stations
3. SDG 15: Life on Land
• Target 15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains, and drylands, in line with obligations under international agreements
• Indicator 15.1.1: Forest area as a proportion of total land area
• Target 15.2: By 2020, promote the implementation of sustainable management of all types of forests, halt deforestation, restore degraded forests, and substantially increase afforestation and reforestation globally
• Indicator 15.2.1: Progress towards sustainable forest management

Analysis

1. Which SDGs are addressed or connected to the issues highlighted in the article?

The issues highlighted in the article are connected to the following SDGs:

• SDG 13: Climate Action
• SDG 14: Life Below Water
• SDG 15: Life on Land

2. What specific targets under those SDGs can be identified based on the article’s content?

Based on the article’s content, the following specific targets can be identified:

• Target 13.1: Strengthen resilience and adaptive capacity to climate-related hazards and natural disasters
• Target 13.2: Integrate climate change measures into national policies, strategies, and planning
• Target 13.3: Improve education, awareness-raising, and human and institutional capacity on climate change mitigation, adaptation, impact reduction, and early warning
• Target 14.1: By 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution
• Target 14.3: Minimize and address the impacts of ocean acidification, including through enhanced scientific cooperation at all levels
• Target 15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains, and drylands, in line with obligations under international agreements
• Target 15.2: By 2020, promote the implementation of sustainable management of all types of forests, halt deforestation, restore degraded forests, and substantially increase afforestation and reforestation globally

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

Yes, there are indicators mentioned or implied in the article that can be used to measure progress towards the identified targets:

• Indicator 13.1.1: Number of deaths, missing persons, and directly affected persons attributed to disasters per 100,000 population
• Indicator 13.2.1: Number of countries that have communicated the strengthening of institutional, systemic, and individual capacity-building to implement adaptation, mitigation, and technology transfer
• Indicator 13.3.1: Number of countries that have integrated mitigation, adaptation, impact reduction, and early warning into primary, secondary, and tertiary curricula
• Indicator 14.1.1: Index of coastal eutrophication and floating plastic debris density
• Indicator 14.3.1: Average marine acidity (pH) measured at agreed suite of representative sampling stations
• Indicator 15.1.1: Forest area as a proportion of total land area
• Indicator 15.2.1: Progress towards sustainable forest management

Table: SDGs, Targets, and Indicators