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Sovereignty and UNCLOS

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United Nations Convention on the Law of the Sea (UNCLOS)

Introduction to United Nations Convention on the Law of the Sea (UNCLOS)

Defining Canada’s extended continental shelf

Canada is working to define the outer limits of its extended continental shelf under the United Nations Convention on the Law of the Sea (UNCLOS).

The Canadian Hydrographic Service (CHS) at Fisheries and Oceans Canada, the Geological Survey of Canada (GSC) at Natural Resources Canada, and Global Affairs Canada, with vessel support from the Canadian Coast Guard and international partners, have collaborated for more than two decades to complete this work.

CHS also contributes bathymetric data collected through the program to the International Bathymetric Chart of the Arctic Ocean (IBCAO) and the Nippon Foundation, Seabed 2030 initiative, supporting global scientific understanding of seafloor mapping.

About UNCLOS

UNCLOS is an international treaty that establishes the legal framework governing ocean activities. Article 76 of the Convention defines the continental shelf and sets out the criteria for establishing its outer limits.

UNCLOS recognizes that coastal states have sovereign rights over the natural resources of the seabed and subsoil of their continental shelf, as well as jurisdiction over certain activities such as marine scientific research.

CHS and GSC are responsible for delivering the scientific components of Canada’s Extended Continental Shelf Program. Their work involves bathymetric and seismic surveys of Canada’s offshore seabed in the Atlantic and Arctic Oceans. These surveys provide information about the depth, shape, distance, and composition of the seabed, as well as the thickness of sediment in the subsoil.

On ship-based expeditions in the Atlantic and Arctic Oceans, teams of hydrographers, supported by technologists, engineers and other scientific personnel operate advanced multibeam echosounder systems to map the seabed in deep waters. In ice-covered areas that are inaccessible to ships, teams deploy by air to conduct surveys from ice camps, adapting methods and equipment to extreme conditions while maintaining strict data quality and safety standards.

About the extended continental shelf

A continental shelf extends from a country’s coastline to the outer edge of its continental margin. Where the continental margin extends beyond 200 nautical miles, a coastal state may establish an extended continental shelf if it can demonstrate that the seabed is a natural prolongation of its land territory. The portion of the continental shelf beyond 200 nautical miles is known as the Extended Continental Shelf (ECS). More than 80 countries, including Canada, are believed to have an ECS.

Canada’s extended continental shelf program

Canada ratified UNCLOS in 2003 and launched its Extended Continental Shelf Program that year. Major scientific survey expeditions to define the outer limits of Canada's continental shelf in the Atlantic and Arctic Oceans began in 2006.

Since then, Canada has:

Canada’s Submission at a Glance

Once Canada's submissions have been reviewed, the CLCS, will issue recommendations. Canada will then establish the outer limits of its extended continental shelf in accordance with the United Nations Convention on Law of the Sea. Limits established on the basis of those recommendations are final and binding. Where the continental shelf entitlements of neighbouring States overlap, Canada will negotiate maritime boundaries through peaceful diplomatic processes.

Atlantic submission

The Atlantic submission on Canada's extended continental shelf

Canada submitted information on the outer limits of its continental shelf in the Atlantic Ocean with the Commission on the Limits of the Continental Shelf on December 6, 2013.

This submission fulfilled Canada’s obligation under UNCLOS to provide information on the limits of its extended continental shelf within ten years of ratifying the Convention. Indigenous organizations, territorial governments and other federal partners contributed expertise, traditional knowledge and logistical support for early surveys.

The area examined in this submission extends beyond 200 nautical miles from Canada’s Atlantic baselines and covers approximately 1.2 million square kilometres of seafloor from Nova Scotia in the south, along the Grand Banks to the northern tip of Labrador.

For analytical purposes, the submission was divided into three regions, each reflecting distinct geological characteristics:

Surveys – Atlantic

Article 76 of UNCLOS establishes the scientific criteria used to determine the outer limits of the extended continental shelf. Applying these criteria requires extensive geological and bathymetric data and detailed analysis.

Atlantic Data Collected Include:

UNCLOS-Specific expeditions in the Atlantic

Canada has undertaken a series of hydrographic surveys to support its continental shelf program. Surveys were conducted:

Most recently, in 2024, a hydrographic survey was completed for the Scotian Shelf to the Newfoundland Ridge.

These targeted surveys filled critical data gaps and complemented existing offshore datasets.

Legacy data (Atlantic)

The Atlantic portion of the UNCLOS submission benefited from Canada’s existing survey data holdings dating back to 1974, plus data collected by other organizations for earlier projects.

Arctic submission

The Arctic Ocean

The Arctic Ocean is the world’s smallest ocean, which covers an area of approximately 14 million square kilometres. Almost half of this ocean region consists of continental shelf areas, many of which are less than 200 metres deep.

Much of the Arctic is covered in ice most of the year and is accessible only during a short summer season. The areas surveyed as part of Canada’s extended continental shelf program lie well north of the Northwest Passage and require long voyages in harsh environmental conditions, far from established support infrastructure.

Several environmental and operational factors make scientific work in the Arctic Ocean particularly challenging.

Extremely cold and unpredictable weather, extensive sea-ice coverage, deep water, and the remoteness of many regions can limit opportunities to collect scientific data. Moving sea ice can also create serious navigation and safety hazards.

Arctic expeditions are costly and may require the support of two icebreakers. Travel through sea ice is often slow, and routes may need to change in response to ice conditions and weather. Successful expeditions also require careful coordination among government agencies, research organizations, and commercial partners.

What Canada submitted

Canada’s Arctic submission, including the 2022 addendum, covers approximately 2 million km2 of seabed and subsoil beyond 200 nautical miles from Canada’s Arctic baselines, consistent with Article 76 of the UNCLOS treaty.

The submission covers offshore geological features extending Canada’s Arctic coastlines, including:

Scientific interpretation

Scientific evidence collected since 2006 supports the interpretation that the Central Arctic Plateau – comprising the Lomonosov Ridge, Alpha Ridge and the Mendeleev Rise is a natural prolongation of Canada’s continental margin, consistent with the criteria set out in Article 76 of UNCLOS.

Extensive bathymetric, seismic, gravity, magnetic and geological datasets indicate that these underwater features are not isolated oceanic structures but are underlain by continental crust extending from the North American landmass beneath the Arctic Ocean. This interpretation forms the scientific basis of Canada’s Arctic continental shelf submission.

Surveys – An ongoing effort

Canada’s Arctic survey program is one of the most ambitious hydrographic mapping efforts undertaken.

The scientific data collected to support Canada's continental shelf program includes:

These datasets were collected during more than 15 major research expeditions, many conducted in partnership with the United States, Denmark, Germany and Sweden. Scientific surveys continue as opportunities and conditions allow, supporting the ongoing technical analysis process.

What happens next

  1. Ongoing surveys – Canada continues to gather scientific data to support the 2022 Addendum to the 2019 Arctic Ocean Submission.
  2. Revised Arctic Ocean Submission in 2030 – Canada intends to file a revised submission incorporating new data gathered in the Arctic Ocean.
  3. CLCS review – When Canada’s Arctic Ocean submission reaches the top of the queue, the Commission on the Limits of the Continental Shelf will evaluate Canada’s scientific evidence against Article 76 requirements.
  4. CLCS recommendations – The Commission issues technical recommendations on scientifically supportable outer limits.
  5. Boundary delimitation – Where applicable, Canada will negotiate final maritime boundaries with neighbouring states through peaceful diplomatic processes.

Data collection: Technology & methods

Acquiring scientific data

Collecting the scientific evidence needed to support Canada’s extended continental shelf submissions has required variety of data acquisition techniques, with international collaboration and years of demanding fieldwork in some of the worlds harshest marine environments.

This section summarizes the primary technologies and methods used to acquire the data for Canada’s Atlantic and Arctic submissions.

Data acquisition methods

To meet UNCLOS requirements, Canadian survey teams worked with the latest technological innovations and combined national and international expertise to pool knowledge, equipment, and resources.

Conventional single beam sonar technology measures water depth along a narrow path beneath the vessel. Modern multibeam echosounder systems (MBES) transmit and resolve hundreds of beams of sound across a wide swath of the seafloor. When processed and gridded, these measurements produce high-resolution, three-dimensional images of the seabed topography (depth and shape). Modern MBES provides complete seafloor coverage along a wide swath, reveals seafloor morphology (shape) used to define the continental margin, and has performed reliably in deep water and challenging Arctic conditions.

Canada - U.S. joint surveys (2007-2011)

Between 2007 and 2011, Canada partnered with the United States to conduct four joint Arctic survey expeditions. The Canadian Coast Guard icebreaker CCGS Louis S. St-Laurent operated alongside the United States Coast Guard icebreaker USCGC Healy, which was equipped with a deep-water multibeam system capable of full-ocean-depth mapping.

During these expeditions, the Louis S. St-Laurent provided icebreaking support while the Healy collected bathymetric data. The vessels then exchanged roles to enable seismic surveys from Louis S. St-Laurent.

Canada’s own deep-water capabilities (2014)

In 2014, Canada acquired its own deep-water MBES, a Kongsberg EM122, installed aboard the CCGS Louis S. St-Laurent. This technological upgrade significantly enhanced Canada’s national capability for independent Arctic surveying.

Processing and quality control

Data collected by a deep-water MBES starts out in raw, unprocessed form. To convert it into accurate depth information, hydrographers apply a series of corrections that account for how sound travels through the ocean and how the vessel itself moves.

These corrections consider factors such as:

Hydrographic teams deploy specialized probes into the ocean to generate sound velocity profiles which are essential for accurate depth measurements.

The Arctic challenge: In the High Arctic, icebreakers navigate through thick ice that can scrape and strike the hull, generating acoustic noise that can be recorded by sonar systems. Additional filtering and cleaning are often required to distinguish seafloor returns from ice-related noise.

Once cleaned and validated, the depth measurements are gridded to render a three-dimensional model of the seafloor.

Autonomous Underwater Vehicle

During survey trips to the Arctic, Canada also used autonomous underwater vehicles (AUVs) to collect data in areas difficult to survey from surface vessels. Assessments of AUV technology and other methodologies for high-resolution bathymetric mapping were conducted as part of a joint CHS-GSC project called Cornerstone (2008-2011).

Ice camps

Ice camp surveys proved invaluable for the areas in the Arctic that are inaccessible to ships, even ice breakers.

Ice camp expeditions

How ice camp surveys work

Ice camp surveys must be conducted in the early spring before the ice breaks up and foggy conditions prohibit aircraft support.

  1. Setup: Ice camp and aircraft runway constructed before survey work begins
  2. Transport: Airplanes carry team members and supplies; helicopters transport hydrographers with specialize ‘through-ice’ echosounding equipment along survey routes
  3. Takedown: Ice camp totally dismantled after survey complete

Through-ice sounding

Hydrographers used ‘through-ice’ echosounders and gravimetres to measure a depth and local gravitational acceleration at a point over the ocean floor. A ‘through-ice’ echosounder can send a sound wave through the sea ice and into the water column. The sound wave then echoed off the bottom of the ocean and to return through the ice to the transducer. To minimize sound loss at the air-ice interface, the transducer is bonded to the ice with a thin layer of bio-degradable oil. At each location a gravity reading was also taken which aided in the mapping of geological structures below the seafloor.

Arctic survey expeditions: Complete list

Eastern arctic

Western Arctic

Understanding Article 76: The science behind the submission

Article 76 of the UNCLOS treaty enables coastal states to define the outer limits of their continental shelf beyond 200 nautical miles where the appropriate scientific criteria are met. Canada’s Arctic submissions are supported by scientific evidence, including the interpretation of offshore features such as the Lomonosov Ridge, Alpha Ridge, and Mendeleev Rise as a part of the natural prolongation of Canada’s continental margin.

Continental margin: Key concepts

The continental margin is the natural underwater prolongation of a country’s landmass offshore before it reaches the deep ocean floor.

Geological components:

  1. Continental shelf – the shallow, gently sloping area adjacent to the coast
  2. Continental slope – where the shelf descends steeply toward deeper ocean basins
  3. Continental rise – the gradual transition zone between the slope and the deep ocean floor

Legal and geological definitions

Under UNCLOS, a coastal state with a narrow continental margin is entitled to a continental shelf out to 200 nautical miles from its baselines. Where the continental margin extends farther, a coastal state may submit information to establish an extended continental shelf to the outer limits of the continental margin.

The extended continental shelf is a juridical definition determined through the application of Article 76 formulas and constraints and must be supported by scientific evidence.

The two formulas

UNCLOS Article 76 outlines two formulas that may be used to establish outer limit lines. States may use whichever formula produces the most advantageous result, subject to the constraint limits.

Formula 1: Foot of slope + 60 nautical miles

Formula 2: Sediment thickness (Gardiner line)

The two constraints

Article 76 also sets maximum constraint limits on how far the outer limit may extend:

States may apply whichever constraint is more advantageous, subject to the rules in Article 76.

The foot of the continental slope

The foot of slope is a critical reference used in applying Article 76 formulas.

Defining the outer limits: Fixed points

Canada’s submissions define outer limits using fixed geographic coordinates (latitude and longitude) that connect to form boundary lines.

How fixed points are determined (high level):

  1. Apply the two formulas (FOS + 60 nm, or sediment thickness)
  2. Apply the two constraints (350 nm, or 2,500 m isobath + 100 nm)
  3. Select the most seaward limit at each location, where permitted
  4. Connect fixed points with geodesic lines not exceeding 60 nautical miles

These fixed points are submitted to the CLCS for review and may be refined through an ongoing technical review process.

Scientific work delivered by CHS

CHS scientific and geomatics contributions to the program include:

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