Ship Stack Emissions in the Arctic - NOx, SOx, 

Black Carbon and Ozone

(from ASMA Report 2009)


Ships are powered by engines and fuels that, like other transportation modes, emit CO2 and water vapor, nitrogen oxides (NOx), sulfur dioxide (SO2), carbon monoxide (CO) and particulate matter (including black carbon BC). Most oceangoing ships burn low-quality residual fuels that tend to contain high amounts of particulates from soot (black carbon), sulfur aerosols, ash and heavy metals.

These are pollutants specifically quantified in the inventory of emissions from Arctic shipping in this assessment. These pollutants are linked with specific environmental effects, and complex interactions occur among these substances in the regional and global atmosphere. For example, NOx is a gaseous contributor to tropospheric ozone formation; SOx gases form particles that contribute to acid rain and cloud effects on regional climate; and other fine particles like black carbon impact air quality, visibility and climate change.

Shipping’s contribution to regional and global impacts from emissions such as CO2, NOx and SO2 have been evaluated by scientists and shown to be significant enough to motivate policy action. However, environmental and climate effects of NOx and ozone, sulfur aerosols and clouds, and black carbon particles in the Arctic are only beginning to be understood. Black carbon has been proven to have significant climate forcing effects, in addition to its effects on snow and ice albedo, accelerating the retreat of Arctic sea ice.

Background levels of NOx, the precursor to ozone, are very low in the Arctic and recent studies have found that seasonal increases in ozone are closely linked to seasonal increases in shipping activity. Surface ozone is known to have harmful effects on plant growth and human health and is the basis for photochemical smog. Ship stack emissions in and near the Arctic will increase along with growth in shipping activity, except where regulations like MARPOL Annex VI require steep reductions in sulfur emissions through fuel sulfur limits or pollution reductions in specially designated regions. The specific benefits of reducing impacts in the Arctic through control of ship emissions need to be further studied, and the AMSA inventory for 2004 provides a good baseline inventory to evaluate scenarios that may achieve these benefits.

Based on AMSA findings, the report recommends continued study of ship-based emissions and trends. Climate change policy is currently focused on CO2 from ships and the potential climate response to lower ship sulfur emissions is becoming recognized. NOx emission controls may mitigate some of the Arctic regional ozone impacts suggested by one international study and the AMSA inventory provides an opportunity to update previous research findings.

More recently, scientists are recognizing that black carbon particles have potentially significant impacts on the vulnerable Arctic environment and climate that need to be quantified. The AMSA contribution to further research may be very important, given that recent studies suggest that reduction of the positive climate forcing due to BC would decrease both global warming and retreat of the sea ice and glaciers and would therefore provide an opportunity for effective short term mitigation of global warming.

The release and deposition of black carbon in the Arctic region is of particular concern because of the effect it has on reducing the albedo (reflectivity) of sea ice and snow.


  •  1. Arctic Marine Shipping Assessment Report 2009

Arctic Council, 2009, Arctic Marine Shipping Assessment (AMSA), Arctic Council.©