Suspended sediment connectivity on the Mackenzie Delta: the first-order importance of channel–lake exchange 

Introduction 

The Mackenzie River Delta is a crucial link in the transport of sediments and nutrients between the huge Mackenzie River basin and the Beaufort Sea. The distributary network of channels and lakes that forms this delta has played a vital role for centuries as communication corridors, connecting local communities in the delta and providing them with access to goods and services from the south. However, current environmental changes, primarily driven by climate change, are accelerating the degradation of permafrost, the formation of deep scour holes, the increasing of water levels in channels and lakes during summer, and the rising levels of the Beaufort Sea. These factors are collectively reducing the water transport capacity of distributary channels within the delta. 

Climate change and permafrost degradation will significantly affect the function of Arctic deltas as "filters/sponges" and sites of sediment retention. For Arctic deltas, it can be hypothesized that accelerated permafrost thaw will dramatically alter the surface area of deltaic lakes, changing the conditions of sorption and desorption of solid particles and chemical compounds. This raises several fundamental questions: 

1. How will sediment delivery to the Beaufort Sea (Arctic Ocean) change in the future? 
2. How will sediments retained in the delta reshape the low-lying tundra landscape and impact the communication isolation of local communities? 
3. How can local communities adapt to changing environmental and hydrological conditions? 

Inspiration and Development of the Research Concept 

This project stems from the research team's extensive prior experience gained through years of studying large river deltas in Siberia, such as the Lena River (Chalov et al., 2023) and the Kolyma River (Chalov et al., 2021; Habel et al., 2023), as well as their significant expertise in modelling the transport of suspended particles in dam reservoirs (Hachaj et al., 2024). The findings of previous research projects, such as INTERACT I KolymaSed and Nordic Centres of Excellence in Arctic Research (Rexcas), provided a strong foundation for further analysis. In 2023, the project leader completed a research internship at the Aurora Research Institute (WARC) in Inuvik as part of the INTERACT III MackSed initiative, funded by the European Commission. Additionally, in 2024, the research team received funding from the Polish Ministry of Education and Science to conduct two projects planned for 2025–2028: 

1. Grant No. 2024/53/B/ST10/03483: Arctic deltas as sponges: How do river deltaic plains now filter and trap sediment and carbon? 
2. Grant No. 2023/50/O/ST10/00597: Evaluation of the settling velocity and trapping capacity of sediments in lakes in the Great Arctic River deltas. 

Objective 

This project aims to map channel–lake hydrological connectivity within the delta plain and evaluate the efficiency of fine-grained sediment trapping dynamics by the channel–lake network, using the Big Lake complex in Inuvik as a case study. We aim to simulate current and potential scenarios of fine-grained sediment transport using 2D and 3D hydraulic models in the central part of the delta, where sediment transport is not constantly monitored. Our objective is to provide a reliable description of how climate change influences the evolution of lakes and water-distributing channels. Furthermore, we plan to disseminate the findings to audiences with both scientific and applied interest in the subject. 

Achieving the project's goals will specifically allow for identifying areas at risk of communication isolation by developing scenarios of changes in the channel–lake network and sediment deposition (e.g., lake disappearance, loss of lake–channel connections, and siltation of main water-distributing channels) that may affect the accessibility of traditional waterways. 

The project will be ensured by the participation of experienced researchers with expertise in: 

1. Conducting fieldwork from the water, including water sampling, depth measurements using sonar, and measuring flow velocities in channel systems. 
2. Implementing Wetland InSAR technology to generate high-resolution images of hydrological connectivity in Arctic delta ecosystems. 
3. Developing 3D numerical sediment transport models for a channel–lake network, based on hydrodynamic modelling and particle tracking using a Lagrangian approach. 

Investigating the impact of fine sediment transport on the stability of distributary channels, including erosion processes (e.g., the development of deep scour holes) and the siltation of navigational routes. 

All tasks outlined in the project align with three key goals relevant to the Inuvialuit Settlement Region: 

1. Preservation of Inuvialuit cultural identity. 
2. Ensuring economic benefits for the Inuvialuit community. 
3. Protection of the region’s environment and wildlife.