Ship emissions measurement in the Arctic by plume intercepts of the Canadian Coast Guard icebreaker Amundsen from the Polar 6 aircraft platform

Abstract. Decreasing sea ice and increasing marine navigability in northern latitudes have changed Arctic ship traffic patterns in recent years and are predicted to increase annual ship traffic in the Arctic in the future. Development of effective regulations to manage environmental impacts of shipping requires an understanding of ship emissions and atmospheric processing in the Arctic environment. As part of the summer 2014 NETCARE (Network on Climate and Aerosols) campaign, the plume dispersion and gas and particle emission factors of effluents originating from the Canadian Coast Guard icebreaker Amundsen operating near Resolute Bay, NU, Canada, were investigated. The Amundsen burned distillate fuel with 1.5 wt % sulfur. Emissions were studied via plume intercepts using the Polar 6 aircraft measurements, an analytical plume dispersion model, and using the FLEXPART-WRF Lagrangian particle dispersion model. The first plume intercept by the research aircraft was carried out on 19 July 2014 during the operation of the Amundsen in the open water. The second and third plume intercepts were carried out on 20 and 21 July 2014 when the Amundsen had reached the ice edge and operated under ice-breaking conditions. Typical of Arctic marine navigation, the engine load was low compared to cruising conditions for all of the plume intercepts. The measured species included mixing ratios of CO₂, NO_x, CO, SO₂, particle number concentration (CN), refractory black carbon (rBC), and cloud condensation nuclei (CCN). The results were compared to similar experimental studies in mid-latitudes.

Plume expansion rates (γ) were calculated using the analytical model and found to be γ  =  0.75 ± 0.81, 0.93 ± 0.37, and 1.19 ± 0.39 for plumes 1, 2, and 3, respectively. These rates were smaller than prior studies conducted at mid-latitudes, likely due to polar boundary layer dynamics, including reduced turbulent mixing compared to mid-latitudes. All emission factors were in agreement with prior observations at low engine loads in mid-latitudes. Ice-breaking increased the NO_x emission factor from EF_NOx  =  43.1 ± 15.2 to 71.6 ± 9.68 and 71.4 ± 4.14 g kg-diesel⁻¹ for plumes 1, 2, and 3, likely due to changes in combustion temperatures. The CO emission factor was EF_CO  =  137 ± 120, 12.5 ± 3.70 and 8.13 ± 1.34 g kg-diesel⁻¹ for plumes 1, 2, and 3. The rBC emission factor was EF_rBC  =  0.202 ± 0.052 and 0.202 ± 0.125 g kg-diesel⁻¹ for plumes 1 and 2. The CN emission factor was reduced while ice-breaking from EF_CN  =  2.41 ± 0.47 to 0.45 ± 0.082 and 0.507 ± 0.037  ×  10¹⁶ kg-diesel⁻¹ for plumes 1, 2, and 3. At 0.6 % supersaturation, the CCN emission factor was comparable to observations in mid-latitudes at low engine loads with EF_CCN  =  3.03 ± 0.933, 1.39 ± 0.319, and 0.650 ± 0.136  ×  10¹⁴ kg-diesel⁻¹ for plumes 1, 2, and 3.