Plastic pollution in the oceans has become an important societal problem, as plastics are the most common and persistent pollutants in oceans and beaches worldwide.

In the common imagination, plastic waste is often associated with bottles drifting in the ocean, fishing gear washing up on beaches or plastic bags that turtles mistake for jellyfish and eat.

But those larger particles are just the tip of the iceberg.

Smaller particles are also an important part of the problem. Plastic particles smaller than five millimetres are called microplastics. They may originate from deliberate design (such as cleaning agents or personal care products), breakdown of larger pieces of plastic or microfibers from textiles.

The impact of microplastics on the environment and human health is still being studied.

Microplastic collection on the Oregon Coast. Photo: Laura / Flickr

Arctic impact

If people assume the Arctic environment is unaffected by what humans discard into the oceans, they are wrong. The pristine waters of the Arctic Ocean are under silent threat by those particles as they drift along with the ocean currents over long distances.

Microplastic concentrations in the Arctic are expected to increase rapidly due to increasing freshwater input and the intensification of shipping traffic and resource development activities.

Plastics are showing up in Canada’s Arctic birds

Given the exceptional vulnerability of Arctic marine ecosystems, there is an urgent need to assess the distribution, pathways and fate of microplastics in the Arctic.

In a recent paper published in Marine Pollution Bulletin, we studied whether and how microplastics could be incorporated within the sea ice structure.

Microplastics within sea ice could impact the absorption of incident solar radiation. This affects sea ice albedo — how the ice reflects solar energy — one of the key properties of sea ice in terms of regulation of the heat exchange between the ocean and the atmosphere.

A sampling of microplastics from a freshwater stream in Florida. Photo: Florida Sea Grant / Flickr

Measuring albedo

Changes in sea ice albedo would have strong consequences on the annual cycle of sea ice growth and melt.

To test our hypothesis, we set up a microcosm study at the Sea-ice Environmental Research Facility at the University of Manitoba, an outdoor pool where we can grow sea ice.

Two sets of 12 microcosms, measuring one cubic metre, were made using galvanized aluminium pipes as frames and cotton bed sheets as walls.

The first set was used to measuring light levels, while the second set was used to collect sea ice samples. We manually added microplastic particles to monitor their incorporation into the sea ice as it grew. We used four different concentrations: control (no particles added), low, medium and high (about 120, 380 and 1,200 particles per litre, respectively).

We used a dye called Nile red to follow the microplastics as the ice froze. Under a fluorescent light, dye caused microplastics to glow, allowing us to see how sea ice concentrates microplastics within its structure and, once incorporated, how those particles remain in the ice matrix.

We found high concentrations of particles at the sea ice surface, due to the particles’ buoyancy and to the rapid formation of ice crystals, trapping the particles as ice coalesces into a firm ice layer.

Albedo is a measurement of how well a surface reflects sunlight. Sea ice that is darker, due to the accumulation of pollution particles or microplastics, absorbs more sunlight. Photo: Alec Cooks / Unsplash

Although microplastics did not affect the sea ice growth rates, we found distinct changes in sea ice albedo in response to medium and high concentrations of microplastics microcosms.

To determine the real-world impact of our observations, we also measured microplastic concentrations from various sea ice samples collected in the Gulf of Bothnia (Baltic Sea).

We observed microplastic concentrations similar to what is observed in the Arctic Ocean (8 to 41 particles per litre), but much lower than the concentration in our microcosms experiment. At those concentrations, we do not expect microplastic incorporation to have any impact on sea ice albedo.

For regions with higher microplastic concentrations, or should microplastic concentration increase, we expect sea-ice properties might change.

These changes would affect most notably albedo, but also photochemical and photo-biological processes occurring in sea ice, such as light availability for algae living at the bottom of the ice cover, with potential impacts on the base of the Arctic food web.

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By Aimée Slangen, Utrecht University and John Church, CSIRO

Global average sea level has risen by about 17 cm between 1900 and 2005. This is a much faster rate than in the previous 3,000 years.

The sea level changes for several reasons, including rising temperatures as fossil fuel burning increases the amount of greenhouse gases in the atmosphere. In a warming climate, the seas are expected to rise at faster rates, increasing the risk of flooding along our coasts. But until now we didn’t know what fraction of the rise was the result of human activities.

In research published in Nature Climate Change, we show for the first time that the burning of fossil fuels is responsible for the majority of sea level rise since the late 20th century.

As the amount of greenhouse gases we are putting into the atmosphere continues to increase, we need to understand how sea level responds. This knowledge can be used to help predict future sea level changes.

Measuring sea level

Nowadays, we can measure the sea surface height using satellites, so we have an accurate idea of how the sea level is changing, both regionally and in the global mean.

Prior to this (before 1993), sea level was measured by tide gauges, which are spread unevenly across the world. As a result, we have a poorer knowledge of how sea level has changed in the past, particularly before 1960 when there were fewer gauges.

Nevertheless, the tide gauge measurements indicate that global mean sea level has increased by about 17 cm between 1900 and 2005.

What drives sea level rise?

The two largest contributors to rising seas are the expansion of the oceans as temperatures rise, loss of mass from glaciers and ice sheets, and other sources of water on land. Although we now know what the most important contributions to sea-level rise are, we did not know what is driving these changes.

Changes in sea level are driven by natural factors such as natural climate variability (for example El Niño), ongoing response to past climate change (regional warming after the Little Ice Age), volcanic eruptions, and changes in the sun’s activity.

Volcanic eruptions and changes in the sun affect sea level across years to decades. Large volcanic eruptions can cause a temporary sea-level fall because the volcanic ash reduces the amount of solar radiation reaching the ocean, thus cooling the ocean.

Humans have also contributed to sea level rise by burning fossil fuels and increasing the concentration of greenhouse gases in the atmosphere.

Separating the causes

We used climate models to estimate ocean expansion and loss of mass from glaciers and ice sheets for each of the individual factors responsible for sea level change (human and natural). To this we added best estimates of all other known contributions to sea level change, such as groundwater extraction and additional ice sheet contributions.

We then compared these model results to the observed global mean 20th century sea-level change to figure out which factor was responsible for a particular amount of sea level change.

Over the 20th century as a whole, the impact of natural influences is small and explains very little of the observed sea-level trend.

The delayed response of the glaciers and ice sheets to the warmer temperatures after the Little Ice Age (1300-1870 AD) caused a sea-level rise in the early 20th century. This explains much of the observed sea-level change before 1950 (almost 70%), but very little after 1970 (less than 10%).

The human factor

The largest contributions to sea-level rise after 1970 are from ocean thermal expansion and the loss of mass from glaciers in response to the warming from increasing greenhouse gas concentrations. This rise is partly offset by the impact of aerosols, which on their own would cause a cooling of the ocean and less melting of glaciers.

The combined influence of these two factors (greenhouse gases and aerosols) is small in the beginning of the century, explaining only about 15% of the observed rise. However, after 1970, we find that the majority of the observed sea-level rise is a direct response to human influence (nearly 70%), with a slightly increasing percentage up to the present day.

When all factors are considered, the models explain about three quarters of the observed rise since 1900 and almost all of the rise over recent decades (almost 90% since 1970).

The reason for this difference can be found either in the models or in the observations. The models could underestimate the observed rise before 1970 due to, for instance, an underestimated ice sheet contribution. However, the quality and number of sea level observations before the satellite altimeter record is also less.

Tipping the scales

Our paper shows that the driving factors of sea-level change have shifted over the course of the 20th century.

Past natural variations in climate were the dominant factor at the start of the century, as a result of glaciers and ice sheets taking decades to centuries to adapt to climate change.

In contrast, by the end of the 20th century, human influence has become the dominant driving factor for sea-level rise. This will probably continue until greenhouse gas emissions are reduced and ocean temperatures, glaciers and ice sheets are in equilibrium with climate again.

Aimée Slangen, Postdoctoral research fellow, Institute for Marine and Atmospheric Research, Utrecht University and John Church, CSIRO Fellow, CSIRO

This article was originally published on The Conversation. Read the original article. Main image: A glacier at South Georgia Island. Credit: Flickr/DavidStanley

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In a CTV interview, Prime Minister Stephen Harper's environment minister Leona Aglukkaq seemed reluctant to admit that climate change was a scientifically proven reality.

Mike De Souza writes for Postmedia News, that "when asked whether the ice was melting in the Arctic, considered by climate scientists to be part of the evidence of global warming, Aglukkaq said there may or may not be changes underway."

During the interview, which was aired during CTV's daily political program Power Play, host Don Martin brought up the issue of disappearing arctic sea ice. Aglukkaq, who represents the riding of Nunavut in Parliament, responded that people like her in the north were "seeing those changes every day, or no changes, what have you."

She also said that "there was a report that came out yesterday, I have not received a copy of that but there's always a debate around science and what's changing."

When Martin asked her directly whether she was personally seeing evidence of climate change in the north, Aglukkaq once again refused to give an unambiguous answer, mentioning that the north had "had a particularly bad summer" with snow, and saying that it was "debatable."

Martin observed that what Aglukkaq was describing meant "changing climate, if not climate change," to which she laughed and said: "But it's also important to look at science and use science to make our decisions as best as we can and but to also continue to work with people in the north."

Minister Aglukkaq seemed reluctant to even say the words "climate change," stopping short of using the term when talking about a conference in Norway of the Climate and Clean Air Coalition to Reduce Short-lived Climate Pollutants.

"I was in Oslo, just recently at the climate ch- ah climate conference, ah environment ministers conference, sorry," she said.

De Souza notes that other members of Harper's cabinet have "openly questioned scientific evidence about climate change," including Natural Resources Minister Joe Oliver. In an April interview, Oliver suggested that that scientists had "recently told us that our fears (about climate change) were exaggerated." He was unable to name said scientists or cite any of their research at the time.

Minister Aglukkaq's office did not initially provide comment on her interview. But following the Postmedia News story on Aglukkaq's comments, spokeswoman Amanda Gordon emailed saying that "Minister Aglukkaq was not casting doubt on climate change."

"Is it possible to correct the story?" Gordon asked Postmedia News.

Gordon also said that the CTV interview was conducted last month, and that Aglukkaq's comments were related to research published by the National Snow and Ice Data Centre. As De Souza writes, "this research confirmed the downward trend in summer Arctic sea ice but did not suggest there was any debate about what was happening."

Figure 1. Arctic sea ice extent for September 13, 2013 was 5.10 million square kilometers (1.97 million square miles). The orange line shows the 1981 to 2010 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data

Credit: National Snow and Ice Data Center

Like Aglukkaq's own comments, her office's response did not provide any specific views on climate change. "Scientific debate regarding our understanding of climate change and its effects on Canada, particularly the North, is what Minister Aglukkaq was referencing," Gordon wrote.

De Souza writes that "Aglukkaq's office has failed to respond directly to questions from Postmedia News asking whether she believes scientific evidence justifies further action to stop the causes of climate change and adapt to its impacts" since her appointment in June.

De Souza notes that the Intergovernmental Panel on Climate Change, a coalition of governments and scientists approved by Harper, has said in its first published report that "human influence has been detected in the warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes."

The report said that human activity, including deforestation and GHG emissions released by fossil fuels, have "very likely contributed to Arctic sea ice loss since 1979."

Aglukkaq's own department, Environment Canada, has predicted average global increases in temperature of at least two degrees Celsius above pre-industrial levels by 2050.

De Souza draws attention to internal briefing notes from 2012 in which Environment Canada calls climate change "the most serious environmental issue facing the world today and carries with it significant impacts on human health and safety, the economy, natural resources, and ecosystems in Canada and throughout the world."

Some months ago, Aglukkaq, then health minister, took over as chairman of the eight-nation Arctic Council and signed a statement expressing an "urgent need" to reach a legally-binding deal to prevent human activity from further exacerbating global warming.

Image Credit: MaRS Discovery District / Flickr

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