Changes in sea ice and future accessibility along the Arctic Northeast Passage

https://doi.org/10.1016/j.gloplacha.2020.103319Get rights and content

Highlights

  • Significant warming was shown in the deep layers with a distinct band on the outer edge of the abyssal zone.

  • The NEP will navigable for OW ships in September in 2021-2025, which would extends to August-December for PC6 ships.

  • The straits near the coast have higher accessibility than that far away from the continents.

Abstract

Retreating Arctic sea ice under rapid warming is projected to continue. A new transarctic route, the Northeast Passage (NEP), may open in the near future, with considerable impacts on global shipping transportation. Comprehensive research on the past changes in sea ice in September and future accessibility along the NEP is essential. In this investigation, an unstructured-grid model was used for accurate fitting to the irregular coastal boundary, and accessibility was assessed under two different shared socioeconomic pathways (SSPs) and two vessel classes with the Arctic transportation accessibility model from 2021−2050. Significant warming was presented in the deep layer in the Arctic seas along the NEP in recent decades (1988−2016), with a distinct band on the outer edge of the abyssal zone. The positive anomaly of seawater temperature moved westward and increased notably in coastal areas, which made sea ice disappear, and the area was dominated by the negative anomaly in the last decade. The NEP is projected to be navigable for open water ships in September from 2021 to 2025, which would extend to August−October during 2025−2050 under both SSP2-4.5 and SSP5-8.5. In addition, Polar Class 6 ships would be capable of crossing the NEP from August to December during 2021−2025 and from July to December during 2026−2050. The Vilkitsky Strait and Dmitrii Laptev Strait, which are close to the coast, have higher accessibility than the Shokalskiy Strait and Sannikov Strait, especially in the next five years.

Introduction

The Arctic had undergone warming in 1910s-1940s and cooling in 1950s-1970s (Soon et al., 2015; Connolly et al., 2017), after which the surface air temperature of the Arctic has likely increased by more than double the global average increase, which is known as Arctic amplification in recent decades (Cohen et al., 2020). Arctic sea ice and glaciers have undergone remarkable mass loss under rapid warming in the Arctic (Chen et al., 2019a; Gui et al., 2019). The sea ice extent was reduced by 3 × 106 km2 from November 1978 to December 2013 (Simmonds, 2015). The 15 year satellite record (2003–2018) depicted losses in sea ice volume at 2870 km3 per decade and 5130 km3 per decade in winter (February–March) and fall (October–November) (Kwok, 2018). In addition, the annual mean ice thickness decreased by 0.58 (±0.07) m per decade over the Arctic Basin during 2000−2012 (Lindsay and Schweiger, 2014). The IPCC special report on the ocean and cryosphere in a changing climate (Pörtner et al., 2019) indicated that the decreasing trend of sea ice would continue, and ice-free regions might be periodically present in the Arctic.

The accessibility of Arctic sea passages has been facilitated by the shrinking and thinning of sea ice (Parkinson and Comiso, 2013), and affected by meteorological and hydrological conditions, especially Arctic cyclones (Simmonds et al., 2008; Simmonds and Rudeva, 2012, Simmonds and Rudeva, 2014), storms (Simmonds and Keay, 2009), and atmospheric frontal activities (Rudeva and Simmonds, 2015). The storms change the moisture of the Arctic basin by the surface evaporation and the atmospheric transports from the south (Luo et al., 2017). Meanwhile, the increasing of moisture has a feedback and promotes the downward longwave radiation down to the surface and provides additional latent heat energy which contributes to the genesis of cyclones (Lee et al., 2017). Many operational factors also affect the navigability of passages and choice of routes, such as meteorological and hydrological conditions, facilities, and draft restrictions (Smith and Stephenson, 2013). However, sea ice is widely regarded as one of the most critical physical hazards restricting the opening and commercial exploitation of Arctic shipping routes (Melia et al., 2016). Three Arctic passages, the Central Passage, Northwest Passage, and Northeast Passage (NEP) (Fig. 1), have been explored to connect the Atlantic and Pacific oceans, among which the NEP has the best navigation conditions (Farré et al., 2014; Melia et al., 2017; Stephenson et al., 2018; Christensen et al., 2019; Tseng and Cullinane, 2018; Silber and Adams, 2019; Wagner et al., 2020). Compared with the customary routes, the NEP can shorten the distance and time from Europe to northwestern Asia by 40% and one-third, respectively, which would help to reduce the expense of transport and environmental pollution (Chen et al., 2019b). In recent years, the sea ice conditions along the NEP have changed substantially and shown a significant reduction, which has improved the accessibility of the NEP (Gui et al., 2019). Future Arctic maritime potential has been assessed under a series of scenarios and factors (Stephenson et al., 2013), such as technically accessible areas (Stephenson et al., 2014; Aksenov et al., 2017), navigation season length (Khon et al., 2010; Ng et al., 2018), and economic viability (Chang et al., 2015; Meng et al., 2016). Arctic shipping potential in the mid-century was investigated for two vessel classes under representative concentration pathway (RCP) 4.5 and RCP 8.5 of seven climate model projections, which showed that open-water ships would be capable of passing through the NEP and would expand in September (Smith and Stephenson, 2013). In addition, Melia et al. (2016) pointed out that the navigable period would double for open-water ships, and European routes to Asia would typically become 10 days faster than the alternatives by mid-century and 13 days faster by late in the century.

With the proceeding of Coupled Model Intercomparison Project Phase 6 (CMIP6), a new set of climate change scenarios, the shared socioeconomic pathways (SSPs), was developed to support the decisions of climate policies (Simpkins, 2017; Zhou et al., 2019), but they have not been used to evaluate the accessibility of Arctic passages. The changes in sea ice along the NEP were influenced by the coast with scales of a few kilometers or less of boundary currents and eddies (Aksenov et al., 2017). Therefore, the mechanisms of realistic and detailed variation should be investigated by past changes in sea ice with high-resolution ocean models. In addition, as vital shipping hubs, some crucial straits are priority regions with ice conditions that should be given close attention due to their direct influences on the accessibility of Arctic passages.

For a better understanding of the NEP, a comprehensive study of the past variations in sea ice and future accessibility is essential. A high-resolution unstructured-grid finite-volume community ocean model (FVCOM) was used to investigate the variation in sea ice along the NEP in recent decades (1978−2016). The Arctic Transportation Accessibility Model (ATAM) from the Arctic Ice Regime Shipping System (AIRSS) was applied to the sea ice concentration and thickness from the high-resolution dataset of the Geophysical Fluid Dynamics Laboratory (GFDL) Climate Model 4 (CM4) of CMIP6, assuming the accessibility of two vessel types (open water and Polar Class 6) under two different climate-forcing scenarios (SSP2-4.5 and SSP5-8.5) in the next 30 years (2021−2050). In addition, the navigability of crucial straits, including the Vilkitsky Strait, Shokalskiy Strait, Dmitrii Laptev Strait, and Sannikov Strait (Fig. 1), was evaluated using the monthly average simulation outputs.

Section snippets

Study area and data

The NEP usually refers to the passage from Murmansk harbor to Vladivostok port. At the same time, the Russian Federation has formally defined it as being from the Kara Strait to the Bering Strait (Russian Federation, 2012), which traverses the Kara Sea, Laptev Sea, East Siberian Sea, and Chukchi Sea. The lane from the Kara Strait eastward to the East Siberian Sea (Fig. 1) was the focus of this study. The accessibility routes vary with bathymetry, vessel size, ice conditions, voyage purpose,

Sea ice changes during 1978-2016

Global and Arctic warming have been definite realities in recent decades, and changes in seawater temperature provide direct evidences. The temperature at the surface layer has been preferred for use in previous studies, but the characteristics of seawater temperature at deep layers indicate long-term accumulation of warming. The variations in seawater temperatures are shown in Fig. 2, which presents significant warming in the NEP throughout the surface layer and bottom layer. The area with

Conclusions

The NEP is one of the potential shipping lanes that could connect the Atlantic and the Pacific under rapid warming in the Arctic. In this investigation, a comprehensive analysis was performed to obtain a good understanding of the past changes in sea ice along the NEP and the future accessibility of the NEP and four crucial straits. The following are the main results.

(1) Significant warming was shown in both layers throughout the NEP in September during 1988−2016, and a distinct band of warm

Discussions

This study was reliant on the sea ice estimates derived from the climate models, but the researches showed that current climate models have some problems in hindcasting observed cryosphere trends. Therefore, it is an exploratory analyses, and the reliability of results explicitly depends on the reliability of the climate model output. The observed decrease in Arctic sea ice extent was significantly underestimated by the global climate models in CMIP3, CMIP5, and even CMIP6 during the satellite

Declaration of Competing Interest

The authors declare no conflict of interest.

Acknowledgements

This work was financially supported by the Frontier Science Key Project of CAS (QYZDY-SSW-DQC021 and QYZDJ-SSW-DQC039), the National Natural Science Foundation of China (41721091), the State Key Laboratory of Cryospheric Science (SKLCS-ZZ-2020), and Foundation for Excellent Youth Scholars of “Northwest Institute of Eco-Environment and Resources”, CAS (grant FEYS2019020). Thanks for the data from Prof. Chen and GFDL, and supervising and funding of Prof. Kang and Prof. You. Our cordial gratitude

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