Melting on Greenland is a major contributor to sea level rise and it has accelerated in recent years (CNN, image from Delphotos/Alamy)

An ice sheet’s mass is determined by the balance of accumulation, mainly from snowfall and ablation, and is driven by melting and calving (the collapse of ice on the edge of the ice sheet). These processes are climate-dependent, and there is a temporal lag between changes in climatic conditions and the emergence of a new glacial mass equilibrium. The graph below shows how Greenland’s mass balance has declined at an accelerating pace over the past few decades. Glacial melting, especially from Greenland and Antarctica, is a major cause of sea level rise, which impacts coastal communities around the world.

This graph shows that the mass balance of the Greenland ice sheet is negative and continuing to decline. A negative balance means that factors reducing mass, like the breaking off and melting of ice, are greater than those adding mass, like snowfall.

A 2022 study published in Nature details this process by examining the imbalance of the Greenland ice sheet’s mass with present climatic conditions. The authors (Box et al. 2022) concluded that a minimum sea level rise of 274 ± 68 mm is locked in to reach equilibrium with the current climate. This figure does not consider sea level rise contributions from other sources, nor varied future warming scenarios. However, all scenarios predict increased warming through the end of the century, meaning further ice loss and greater sea level rise. 

Sea level rise presents a variety of issues to low-lying communities, including flooding and saltwater intrusion. Bangladesh, which lies mostly within the Ganges River Delta, is particularly vulnerable to such impacts. Sea level rise impedes drainage from the Delta into the Indian Ocean, thereby increasing flood risk in times of high precipitation and/or river discharge. A higher average sea level also increases the likelihood of extremes in sea level and coastal flooding. Recent floods in June 2022 affected 7.2 million people in Bangladesh, demonstrating the urgency of the current situation and providing a bleak warning for the future. 

This satellite image of the low-lying Ganges Delta, composed of many weaving waterways, illustrates how it can be vulnerable to flooding and salinity intrusion via sea level rise (Credit: European Space Agency)

At the same time, sea level rise is responsible for salinity intrusion along the coast of Bangladesh. Just as glacial mass is the product of accumulation and ablation, salinity results from the balance of freshwater flowing out through the Ganges Delta and seawater pushing up into the coast. As the sea level rises, saltwater is driven progressively further into Bangladeshi lands and waterways. This taints sources of drinking and irrigation water and renders affected lands unsuitable for agriculture. According to the Bangladesh Soil Resources Development Institute, the land area affected by salinity has risen from 83.3 million hectares in 1973 to 105.6 million hectares in 2009. 

The Sundarbans, a huge mangrove forest along the brackish waters of Southern Bangladesh, plays an important role in regulating storm surges. The dense forest provides protection against flooding and salinity intrusion. Still, as the frequency and intensity of surges increase, the Sundarbans is at risk. The forest suffers structural damage from severe flooding, and many mangroves are adapted to survive at lower levels of salinity than those currently present. Damage to the Sundarbans ecosystem reduces its capacity to buffer the negative impacts of sea level rise in Bangladesh, illustrating why urgent action is needed to prevent a disastrous feedback loop. 

The Sundarbans of Bangladesh is the world’s largest mangrove forest, acting as a buffer against sea level rise and salinity intrusion (Generated using AI with Kapwing)

The situation in Bangladesh is just one example of how people around the world are affected by sea level rise. With 40% of the world’s population residing in coastal areas, billions of people are exposed to similar risks. Heavy emitting countries must prioritise the mitigation of greenhouse gas emissions to limit damages as much as possible. Still, with Greenland ice loss and further SLR locked in for the future, climate vulnerable countries like Bangladesh need to act now to strengthen adaptive capacity and respond to climate impacts that are already wreaking havoc. 

Want to learn more about how the Arctic drives global risks? Explore our Global Risks page.