Why have Greenland's crystal blue lakes turned brown?

Why in the NEWS?

• A new study has revealed that extreme weather events are changing Greenland's lakes from their traditional nature. 

Key Points:

• More than 7,500 lakes in western Greenland which previously acted as carbon sinks (absorbing carbon dioxide), are now turning into a major source of carbon dioxide.
• Due to extreme weather events in 2022, these lakes have not only turned brown but are now emitting atmospheric carbon dioxide.

What will you read next in this topic?

1. Extreme weather events cause sudden changes in Greenland lakes.
2. What happened?
3. Effects of extreme weather.
4. Why it matters?
5. The role of atmospheric rivers.
6. A call to action.

Extreme weather events cause sudden changes in Greenland lakes

• A recent study has revealed that more than 7,500 lakes in western Greenland have undergone dramatic changes.
• Once crystal blue, these lakes have turned brown, emitted carbon dioxide and water quality has deteriorated significantly.
• This change, shows the immediate impact of climate change on delicate ecosystems.
• The study, published in the journal Proceedings of the National Academy of Sciences, shows how these events have accelerated ecological changes in Greenland lakes at an unprecedented pace.

What happened?

• Usually, Greenland receives snowfall in the autumn season from late August to late September.
• However, in 2022, above-average temperatures caused the snowfall to turn to rain.
• The warming also caused permafrost to melt—frozen ground that contains significant amounts of organic carbon. 
• As the permafrost melted, it released carbon, iron, magnesium and other elements. 
• These materials were then carried into the lakes by record-breaking rainfall, resulting in dramatic changes in them. 
• The study found that these rapid changes occurred only a few months after extreme weather events, whereas such ecological shifts usually take centuries.
• This sudden change was driven primarily by atmospheric rivers.
• Narrow bands in the atmosphere that transport large amounts of water vapour from tropical regions to other parts of the world.
• While atmospheric rivers contribute to essential precipitation and freshwater supplies, strong systems can bring extreme rainfall, flooding and heat.
• According to 2018 research from NASA, global warming is expected to make these atmospheric rivers longer, wider and more intense by the end of the 21st century. 
• Models suggest that atmospheric river activity could increase by 50-290% in regions such as Greenland, western North America, eastern Asia, Western Europe and Antarctica.

Effects of extreme weather

• As organic carbon and other elements flowed into the lakes, the physical, chemical, and biological properties of the water changed drastically.
• By July 2023, the effects of the 2022 extreme weather events were still evident:

Degradation of water quality:

• The color, odour, and taste of the lakes changed significantly, making the water less suitable for drinking.
• Increased dissolved organic matter from thawed permafrost and precipitation and combined with chlorination processes may produce trihalomethanes, a by-product that is considered carcinogenic.

Disruption of photosynthesis:

• The browning of the lakes reduced the penetration of sunlight, which is essential for phytoplankton.
• These microbes play a key role in absorbing atmospheric carbon dioxide through photosynthesis.
• With less sunlight, the ability of phytoplankton to sequester carbon decreased, leading to a decline in carbon dioxide absorption.

Increased carbon emissions:

• Organic matter in lakes began to break down, releasing carbon dioxide into the atmosphere. 
• This change transformed lakes from carbon sinks to significant carbon sources. 
• The study recorded a 350% increase in carbon dioxide emissions from lakes, further worsening the climate crisis.

Ecological imbalance:

• The change in the composition of lakes benefited organisms that depend on organic carbon pathways more than those dependent on sunlight.
• This change disrupted the ecological balance of these water bodies.

Why it matters?

• The findings of this study come after another report published three months ago, which showed that terrestrial ecosystems had temporarily reduced their carbon absorption capacity.
• Forests, plants and soils – which collectively absorb about half of human carbon emissions – are becoming less effective at reducing emissions.
• In 2023, these natural carbon sinks removed only 0.23 to 0.65 gigatons of carbon, the lowest level since 2003 and three times less than the average of the previous decade.
• This decline in the efficiency of natural carbon sinks, as well as the transformation of lakes into carbon sources, raises concerns about accelerating global warming.
• The Earth’s oceans, forests, soils and other natural carbon sinks play a vital role in maintaining climate stability.
• However, as these systems falter, atmospheric carbon levels are expected to increase significantly.
• The planet is already grappling with record levels of greenhouse gas emissions.
• According to the Global Carbon Budget report, global carbon dioxide emissions are projected to reach 40.6 billion metric tons in 2023 and could rise to 41.6 billion metric tons in 2024.
• With natural carbon sinks weakened and ecosystems like Greenland’s lakes sequestering more carbon, the global climate crisis is set to get even worse.

The role of atmospheric rivers

• Atmospheric rivers are a key factor in the transformation of Greenland's lakes.
• These events are responsible for transporting moisture around the world and are essential for maintaining freshwater supplies.
• However, as global temperatures rise, atmospheric rivers are becoming more intense and frequent.
• According to studies, by the end of the century, atmospheric river activity could occur about three times more frequently than today in regions such as Greenland.
• These intense systems are expected to bring longer periods of heavy rainfall, which could lead to flooding, permafrost thaw, and increased emissions of organic carbon.
• Such scenarios pose significant risks not only to Greenland's lakes but also to other ecosystems that depend on stable water cycles.

A call to action

• The abrupt transformation of Greenland's lakes is a stark reminder of the far-reaching consequences of climate change.
• As the planet warms, extreme weather events are becoming more frequent and severe, leading to rapid and sometimes irreversible ecological changes.
• Urgent action is needed to mitigate these impacts.
• Reducing greenhouse gas emissions, investing in renewable energy, and adopting sustainable practices are essential steps in tackling climate change.
• Additionally, monitoring and protecting vulnerable ecosystems like Greenland's lakes can help maintain their role as natural carbon sinks and safeguard the livelihoods of communities that depend on them.
• The findings of this study underscore the importance of addressing climate change as a global priority.
• Failure to act now could lead to even more dramatic changes to Earth's ecosystems, exacerbating the climate crisis and threatening the future of the planet.