Abstract. This paper presents 5 km×5 km Arctic emissions inventories of important greenhouse gases, black carbon and other pollutants under existing and future (2050) scenarios that account for growth of shipping in the region, potential diversion traffic through emerging routes, and possible emissions control measures. These high-resolution, geospatial emissions inventories for shipping can be used to evaluate Arctic climate sensitivity to black carbon (a short-lived climate forcing pollutant especially effective in accelerating the melting of ice and snow), aerosols, and gaseous emissions including carbon dioxide. We quantify ship emissions scenarios which are expected to increase as declining sea ice coverage due to climate change allows for increased shipping activity in the Arctic. A first-order calculation of global warming potential due to 2030 emissions in the highgrowth scenario suggests that short-lived forcing of ∼4.5 gigagrams of black carbon from Arctic shipping may increase global warming potential due to Arctic ships' CO 2 emissions (∼42 000 gigagrams) by some 17% to 78%. The paper also presents maximum feasible reduction scenarios for black carbon in particular. These emissions reduction scenarios will enable scientists and policymakers to evaluate the efficacy and benefits of technological controls for black carbon, and other pollutants from ships.

The Arctic is a sensitive region in terms of climate change and a rich natural resource for global economic activity. Arctic shipping is an important contributor to the region's anthropogenic air emissions, including black carbon – a short-lived climate forcing pollutant especially effective in accelerating the melting of ice and snow. These emissions are projected to increase as declining sea ice coverage due to climate change allows for increased shipping activity in the Arctic. To understand the impacts of these increased emissions, scientists and modelers require high-resolution, geospatial emissions inventories that can be used for regional assessment modeling. This paper presents 5 km×5 km Arctic emissions inventories of important greenhouse gases, black carbon and other pollutants under existing and future (2050) scenarios that account for growth of shipping in the region, potential diversion traffic through emerging routes, and possible emissions control measures. Short-lived forcing of ~4.5 gigagrams of black carbon from Arctic shipping may increase climate forcing; a first-order calculation of global warming potential due to 2030 emissions in the high-growth scenario suggests that short-lived forcing of ~4.5 gigagrams of black carbon from Arctic shipping may increase climate forcing due to Arctic ships by at least 17% compared to warming from these vessels' CO₂ emissions (~42 000 gigagrams). The paper also presents maximum feasible reduction scenarios for black carbon in particular. These emissions reduction scenarios will enable scientists and policymakers to evaluate the efficacy and benefits of technological controls for black carbon, and other pollutants from ships

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Lower emission freight transport is an issue of concern for government due to the important contribution of goods movement to GHG emissions and, increasingly, a concern shared by industry due to an apparent synergy between CO 2 energy efficiencies and reduced transport fuel costs. A number of technology efforts within freight modes (truck, rail and ship) aim to improve future in-mode performance, including recent and ongoing studies of energy-saving or lowemission shipping technologies. Additionally, mode rebalancing is a key operational alternative to achieve large-scale CO 2 reductions in freight networks [1-6]. The IPCC Fourth Assessment report concerning transportation and infrastructure noted that " freight transport is considerably more conscious of energy efficiency considerations than passenger travel because of pressure on shippers to cut costs, however this can be offset by pressure to increase speeds and reliability and provide smaller ' justin-time' shipments" [7]. Modal shifts that may increase the use of waterborne transport were identified as a primary means of large-scale decarbonization of the freight sector [6]. Infrastructure changes such as improved intermodal access to regional shipping are important enablers for reconfiguring freight networks. Perhaps the largest single infrastructure change to occur this decade is the expansion of the Panama Canal, to be completed in 2014 [8,9,101,102]. This expansion will enable containerized vessels using the canal route to carry up to three-times more cargo, measured in 20-foot equivalent units (TEUs). Large vessels will be more CO 2and energy-efficient, per TEU, than vessels transiting under current canal limits. While larger ships using an expanded canal will likely reduce the CO 2 footprints of cargoes previously carried by smaller ships through the canal, we consider whether GHGs and other emissions may be reduced by some degree of mode shift (cargo diversion) from the so-called North American land bridge to a canal route serving east coast destinations.

Global shipping pattern is widely used to assess vessel-borne pollution risk and inform environmental policymaking. Due to ice retreat under climate change, new trans-Arctic navigation routes may become feasible and change the shipping and pollution pattern. Motivated by inconsistent conclusions on the economic feasibility of Arctic routes of the literature, this article performs modelling to examine the potential for general diversion pattern to the trans-Arctic routes of the global shipping traffic. While we find some trans-Arctic routes are economically feasible, the diversion potential of trans-Arctic routes may be overestimated. The sample in this work contains 522,691 shipping moves. Results show that a mere 83 moves would reduce distance and 45 would save sailing time through the Arctic; however, 20 moves would reduce shipping cost. Though few diversions may happen, we find that 20 economically feasible trans-Arctic diversions reduce GHG emissions. Their average fuel consumption reduction through the Arctic is 264 metric tons (MT) (reduced by 26%); the range is 125-328 MT. The average CO 2 e emission is 767 MT (reduced by 24%); the range is 359-954 MT. Most of these voyages are between North America and East Asia. Ship operators may consider making a diversion to achieve the GHG abatement goal.