In recent years, there has been an increasing concern about the implications of the changing soundscape of the oceans1 (Duarte et al., 2021). In the Arctic, where underwater noise has doubled within only six years2 (PAME, 2019), there is a clear need to assess and govern the risks related to underwater noise pollution3 (Ghosh & Rubly, 2015). As shipping activity in Arctic waters is on the rise4 (Müller et al., 2023) and expected to increase further, it is important to understand better the causes and consequences of shipping noise in these extreme and vulnerable environments.
Climate change-induced warming and sea ice reduction enable vessels to go deeper into the Arctic. The so-called “last chance” tourism has led to rapid growth in cruise expeditions in the Arctic with new risks for humans and the environment5,6,7 (Johannsdottir et al., 2021; Lemelin et al., 2010; Veijola & Strauss-Mazzullo, 2019). The luxury cruise expedition icebreaker Le Commandant Charcot of the French cruise operator Ponant was the first passenger vessel to reach 90° North in 2021 and for the first time with passengers in 20228 (Polar Journal, 2022).
Expedition cruises differ from transiting maritime activities related to transport and cargo as expedition vessels spend prolonged time cruising and manoeuvring in the same area9 (Halliday et al., 2018). They engage in further activities such as driving with speedboats and utilising underwater remotely operated vehicles or helicopters that potentially cause more local noise disturbance. This is a concern, as single and combined noise from such shipping activities in the Arctic Ocean disturbs marine life, adding to cumulative pressures from climate change and other anthropogenic impacts10 (Hauser et al., 2018). Existing studies have mainly addressed global shipping noise emissions from vessels travelling between destinations with implications for larger areas, targeted species impacts, ship traffic trends, or ambient noise levels (e.g. 11,12,13,14,15,16,17,18,19 Aulanier et al., 2018; Ahonen et al., 2017; Escajeda et al., 2023; Halliday et al., 2017; Halliday et al., 2022; Jalkanen et al., 2022; Kochanowicz et al., 2021; Sanjana et al., 2021; Veirs et al. 2016). According to our knowledge, this is the first study looking into context-specific shipping noise caused by cruise expedition vessels in the Arctic, which might reveal novel aspects for governance and future research.
The objective of this paper is to explore the sources and consequences of shipping noise from cruise expedition activities in the Arctic, and to provide recommendations for policymakers and the industry to mitigate noise pollution and thus enhance environmental safety. The paper builds on a structured literature review and eight problem-centred expert interviews. Conceptually, data analysis was inspired by the safety-barrier model, which has been developed in safety science and has been used in diverse industries to enhance safety and prevent incidents. As we will demonstrate, the model is of high relevance to better understand the diversity of ways to deal with noise as a potentially hazardous energy20 (Kjellén & Albrechtsen, 2017). First, we gathered contextual knowledge about the sources and consequences of shipping noise for endemic Arctic marine mammals. Second, we investigated possible mitigation measures and related governance options.
The next sections present background knowledge about cruise expeditions in the Arctic, known impacts of shipping noise on marine mammals, and the employed legal framework. The results and discussions will first consolidate and examine the main cause-effect relationships of shipping noise from Arctic cruise expedition vessels and potential impacts on endemic marine mammals. Consequently, we review safety barriers to mitigate noise impacts and propose a practical approach to precautionary governance of shipping noise from expedition cruises in the Arctic. The paper concludes with the key findings and implications for future action in research and regulation.
Cruise expeditions in the Arctic
Polar cruise expeditions are characterised by adventure, wilderness, education and personal experience21 (Dawson et al., 2014). Modern cruise expeditions in the Arctic are rapidly increasing in number and geographical coverage. Climate-change-induced sea ice retreat facilitates extended navigation and urges people to visit the Arctic as a last Frontier5,6,21,22 (Dawson et al., 2014; Johannsdottir et al., 2021; Lau et al., 2023; Lemelin et al., 2010). Expedition vessels are categorised as passenger vessels, defined as any vessel carrying 12 or more passengers23 (IMO, 1974). Expedition cruise vessels are smaller in size and passenger capacity than conventional cruise vessels (meaning coastal ferries and overseas destination cruises) and usually comprise 20 to 500 passengers24 (van Bets et al., 2017). However, expedition cruises do not travel on direct routes and do not spend the night at busy port sites like conventional cruise ships do. Instead, their purpose is to explore the landscape, encountering wildlife both on and off the vessel, accessing remote shorelines and sea ice, venturing into challenging waters, and seeking exclusive opportunities on a relatively flexible itinerary to experience the Arctic first-hand21,24 (Dawson et al., 2014; van Bets et al., 2017). Expedition cruises in the Arctic encompass a multitude of considerations concerning the vulnerable natural environment, the challenging safety hazards at sea and land, and the concern about lacking search and rescue infrastructure5,25,26 (Browne et al., 2022; Johannsdottir et al., 2021, Stocker et al., 2020). Arctic-bound expedition cruise vessels share similar requirements and characteristics with cargo and tanker vessels under international maritime regulatory frameworks, including the International Code for Ships Operating in Polar Waters (the Polar Code)27 (IMO, 2014a). In addition to global regulations, operators may address these challenges through a collective self-governance approach24 (van Bets et al., 2017), such as membership in the Association of Arctic Expedition Cruise Operators (AECO).Its operational guidelines for members and recommendations are "dedicated to managing responsible, environmentally friendly and safe Arctic tourism and striving to set the highest possible operating standards" (https://www.aeco.no/) and convey a close linkage of human and environmental safety for shipping in the Arctic. However, as of today, AECO's guidelines do not address underwater noise pollution.
Impacts of shipping noise on marine mammals
Noise is invisible to the human eye and may be more challenging to grasp than other anthropogenic impacts on the marine environment, such as plastic and oil pollution, bycatch, entanglement or ship strikes of marine animals. The known impacts of anthropogenic sounds on marine mammals comprise disruption of behaviour (e.g., feeding, breeding, resting, migration), masking of essential sounds, temporary or permanent hearing loss, physiological stress or physical injury, and changes to the ecosystems that result in a reduction of prey availability28 (Moore et al., 2012). These impacts may lead to a displacement of marine mammals3 (Ghosh & Rubly, 2015), with cascading effects on the local and global ecosystems and local communities29 (Lancaster et al., 2021).
From the perspective of a receiving marine organism, sound can be a signal that contains vital information about the environment and its inhabitants28 (Moore et al., 2012). It facilitates critical functions such as acoustic sensing, communication, navigation and feeding by marine fauna, including marine mammals, fish and invertebrates30 (Au and Hastings, 2008). Noise is any other form of sound that either does not provide any helpful information (background clutter), interferes with the biological relevant signals (masking), or causes stress, disturbance, temporal hearing loss, permanent injury, or death28,29,31,32 (Farcas et al., 2020; Lancaster et al., 2021; Moore et al., 2012; Southall, 2008). In addition to the growing number of studies investigating the acute consequences of shipping noise on marine mammals, Erbe et al. (2018)33 developed a population consequence of disturbance (PCoD) model to identify long-term impacts. An example would be how noise affects foraging, leading to reduced energy intake or additional energy expenditure by the behavioural or physiological response, impacting maternal fitness, reducing the birth rate and pup health and potentially leading to pup or adult death. Despite the continuously growing research on the adverse effects of shipping noise on the marine environment within the Arctic, legally binding agreements remain challenging34,35,36,37 (Chang & Xu Zhang, 2021; McWhinnie et al., 2018; Vakili et al., 2020; Wienrich et al., 2022).
A legal framework for shipping noise in the Arctic
Shipping noise is currently recognized as a pollutant in environmental discussions29,31,34,38,39 (e.g. Chang & Zhang, 2021; Chou et al., 2021; Farcas, 2020; Lancaster et al., 2021; Vakili, 2021). Looking at the general legal framework governing human activities at sea, the United Nations Convention on the Law of the Sea (UNCLOS) defines pollution as:
“Pollution of the marine environment means the introduction by man, directly or indirectly, of substances or energy into the marine environment, including estuaries, which results or is likely to result in such deleterious effects as harm to living resources and marine life, hazards to human health, hindrance to marine activities, including fishing and other legitimate uses of the sea, impairment of quality for use of sea water and reduction of amenities.” (UNCLOS, article 1(1).)
Hence, in defining pollution, UNCLOS makes the important distinction between substances and energies. International shipping, however, is mainly regulated through the International Maritime Organization (IMO), which since its establishment in 1948, has focused on safety, environmental concerns, and preventing pollution from ships. Two main conventions negotiated through and adopted by IMO govern safety and the protection of the marine environment: The Convention for the Safety of Life at Sea (SOLAS), which entered into force in 1965, and The International Convention for the Prevention of Pollution from Ships (MARPOL), which entered into force in 1983.
SOLAS specifies the minimum standards for construction, equipment, and operations of ships concerning their safety. Regulations in SOLAS target “safety of life at sea, safety and efficiency of navigation and protection of the marine environment” (e.g. Regulations: 6 – Ice Patrol Service, 10 – Ships’ routeing, 11 – Ship reporting systems, 12 – vessel traffic services, 34 – safe navigation and avoidance of dangerous situations).
In contrast to UNCLOS, MARPOL defines pollution as a substance only, and not as an energy.:
Any substance which, if introduced into the sea, is liable to create hazards to human health, to harm living resources and marine life, […]. (article 2(2))
The six MARPOL Annexes are dedicated to preventing pollution by oil, noxious liquid substances, harmful substances carried by sea in packaged form, sewage from ships, garbage from ships and air pollution from ships. While MARPOL focuses on harmful substances, and SOLAS focuses on safety at sea, UNCLOS introduced the term “energy” as a source of pollution. Considering noise as harmful energy, noise pollution is implicitly addressed by UNCLOS but not by MARPOL or SOLAS40 (Giannoumis, 2017).
In 2014, IMO introduced the Guidelines for the reduction of underwater noise from commercial shipping to address adverse impacts on marine life41 (IMO, 2014b). It comprises a set of non-mandatory guidelines that can be applied by any commercial ship to reduce shipping noise by focusing on primary sources associated with propeller hulls, machinery and operational aspects. However, the guidelines for reducing underwater noise lack practical advice on how certain elements, such as operational measures, should be implemented35 (McWhinnie et al., 2018).
The Arctic Ocean poses a special case for shipping activities and related human and environmental risks. Shipping in the Arctic is strongly characterised by what Albrechtsen and Indreiten (2021)42 define as the Arctic Operational Context and by what Chircop (2020)43 refers to as the Arctic Navigational Context, such as cold and harsh weather conditions, remoteness, lack of infrastructure, lack of knowledge and the strong and unpredictable influence of climate change. In 2014, the growing concerns about risks posed to human operations and the Arctic environment by increasing shipping led IMO to adopt the Polar Code, a mandatory and legally binding regime for navigation in polar waters that is divided into safety-related measures (part I-A) and pollution prevention (part II-A). Further recommendatory provisions are made for both (parts I-B and II-B). The Polar Code addresses risks in polar waters and covers design, construction, equipment, operational, training, search and rescue, and environmental protection matters27 (IMO, 2014a). Its scope is mandatory for individual ships under SOLAS and MARPOL44 (Karahalila et al., 2021). Ships intending to operate in polar waters must undergo a polar classification associated with the level of ice-infested waters their design will facilitate. The assessment involves identification of operational limitations and defining plans, procedures, and safety appliances necessary to mitigate incidents that might interfere with safety or lead to environmental consequences. In addition, vessels must carry a Polar Water Operational Manual (PWOM) regarding the operational capabilities and limitations to support decision-making. The Polar Code does currently not address underwater pollution, which has been identified as one of its implementation gaps45 (Prior, 2022).
Since maritime transport is transboundary and operates between areas within and beyond national jurisdiction, the introduced legal framework
(Fig. 1) is relevant in discussions about policy-making for shipping noise in the Arctic3,35,46 (Ghosh & Rubly, 2015; McWhinnie et al., 2018; Reeves et al., 2014).