Every summer, as the sea ice surrounding Antarctica retreats, tens of thousands of tourists and scientists flock to the landmass by boat and plane. The remote continent is becoming more and more accessible – in the 2019-2020 season the number of tourist visitors reached 74,000, with the vast majority traveling by boat. Scientific activities on the continent are also significant, with more than 70 research stations collectively housing thousands of researchers.
This activity, which is expected to increase in the future, leaves a physical footprint with lasting consequences. By seeking to study or marvel at one of the last (almost) untouched places on earth, humans are having a growing impact that can be measured and quantified.
Under the Antarctic Treaty, tourism and scientific operators are required to remove waste from the continent. Garbage and human waste are airlifted or shipped off the mainland for disposal at warmer latitudes. But some forms of waste are not so easily removed from the continent.
All activities in Antarctica – from power drills for scientific ice coring to transport vehicles – consume fuel. When we burn fuel to keep us warm or to get around, our activities release microscopic particles of “black carbon” (smoke and soot).
Elsewhere in the world, black carbon is released in huge amounts by forest fires and human activity. It travels great distances – soot from the Australian bushfires in 2019-20 circled the globe. However, in Antarctica, which is isolated from the rest of the world by a strong “barrier” of circumpolar winds, the sources of black carbon are generally more local.
New research in the journal Nature Communication has extensively quantified black carbon levels in snow near human settlements. Scientists first collected samples from 28 sites across a 2,000 km stretch of the busiest section of Antarctica, stretching from the Antarctic Peninsula to the interior of the Antarctic Ice Sheet. West Antarctica.
By analyzing the amount and type of light-absorbing particles in snow samples, researchers are documenting how soot emitted by humans affects the properties of Antarctic snow near high-traffic areas.
The samples were passed through filters and analyzed for their optical properties to identify the amount and type of particles. Many types of light-absorbing impurities exist in Antarctic snow, although in trace amounts – the background level of black carbon in Antarctic snow is about 1 nanogram (one billionth of a gram) per gram of snow .
To differentiate the dust from carbon black, the researchers used the “angstrom exponent”. Simply put, smaller particles will absorb a greater band of light than larger ones – so the type of particles in snow samples could be inferred from how the filtered particles interacted with light in the lab.
All samples from nearby human settlements showed black carbon levels well above typical Antarctic background levels, a clear sign of human emissions. High levels of black carbon will influence how snow absorbs light, a property called “albedo”.
Snow with a lower albedo will melt faster. Accordingly, the black carbon content in collected snow samples could be used to infer whether snowmelt rates might have increased due to human activity.
Scientists versus tourists
The results are sobering. In affected areas close to human settlements on the Antarctic Peninsula, human-produced black carbon can melt surface snow by up to 2.3 mm each summer. Looking specifically at tourism activities, the authors calculate that each visitor between 2016 and 2020 actually melted around 83 tonnes of snow, largely due to cruise ship emissions.
Scientific activities are not exempt – in fact, scientific research stations contribute an order of magnitude higher per capita snowmelt rate through the operation of fuel-intensive equipment and vehicles, sometimes all year.
This research confirms similar studies elsewhere on the role of black carbon emissions in accelerating the melting of ice and snow. For example, fires in the Amazon rainforest have increased the rate of glacier melt in the Andes.
In Antarctica, documentation of black carbon near colonies echoes other research on microscopic pollution, such as microplastics found in sea ice and penguins. These results show that human impacts can be more pervasive and insidious than they appear from a distance.
As human activity in Antarctica increases, so will the accompanying effects. Research into these actual and potential harms provides vital information on how best to mitigate them or avoid them altogether. To minimize damage to wildlife and the environment, we must ensure that research and tourism are carefully managed.
Matthew Harris is a PhD researcher in climate science at Keele University.
This article first appeared on The Conversation.