The U.S. exclusive economic zone (EEZ)¹—ocean waters generally between 3 and 200 nautical miles (nmi) seaward from the U.S. coastline—is, according to the National Oceanic and Atmospheric Administration (NOAA), the largest in the world.² The U.S. EEZ and the seabed beneath it encompass diverse marine ecosystems and contain natural resources of economic value and national security interest. Areas of the seabed beyond the 200-nmi outer limit may contain additional natural resources of interest. Several federal departments and agencies map and characterize areas of the ocean both within the U.S. EEZ and beyond the 200-nmi limit to better understand potential U.S. sovereign rights to the resources in these areas, among other purposes.³

The United States is not a signatory to the 1982 United Nations (U.N.) Convention on the Law of the Sea (UNCLOS), which describes internationally recognized maritime zones (Figure 1). However, some members of the executive branch have stated that some (but not all) portions of UNCLOS reflect customary international law. For example, the Department of State reports, "The Convention generally reflects customary international law binding on all countries, including the provisions in Article 76 pertaining to delineating the outer limits of the continental shelf."⁴ In general, the United States follows the UNCLOS framework for establishing maritime zones. For example, presidential proclamations have established the U.S. EEZ;⁵ the U.S. territorial sea, the area that extends 12 nmi seaward from the U.S. coastline;⁶ and the U.S. contiguous zone, an area adjacent to and beyond the territorial sea that extends seaward up to 24 nmi from the U.S. coastline (Figure 1).⁷

UNCLOS establishes ocean sovereign rights for coastal countries for the purposes of exploring, exploiting, conserving, and managing natural resources of the seabed and waters within 200 nmi of the country's normal baseline (i.e., low-water line along the coast).⁸ UNCLOS refers to the seabed that extends 200 nmi from a coastal country's baseline and lies beneath the EEZ as the continental shelf.⁹ Natural resources that may occur on or in the sediments of the continental shelf include petroleum resources (e.g., oil, natural gas, methane hydrates), mineral deposits (e.g., polymetallic nodules, ferromanganese crusts, polymetallic sulfides),¹⁰ and sedentary organisms (e.g., corals).¹¹ Some of these resources also may occur in areas beyond national jurisdiction—the seabed and subsoil beyond the 200-nmi continental shelf is referred to as the Area (Figure 1).¹² Under Article 76 of UNCLOS, a coastal country interested in expanding its national jurisdiction beyond the 200-nmi limit of the continental shelf may submit geological and geophysical evidence for an extended continental shelf (ECS) to a U.N. commission, particularly if the country sees opportunities to capitalize on potential resources of the seabed in this area (see "Commission on the Limits of the Continental Shelf," below).¹³ An ECS would allow countries to exercise sovereign rights over the natural resources of the seabed and subsoil beyond the 200-nmi limit.¹⁴

Figure 1. Maritime Zones (consistent with the United Nations Convention on the Law of the Sea)

Source: Figure modified by the Congressional Research Service. Department of State, "Maritime Zones," https://www.state.gov/about-ecs/maritime-zones/. Notes: Although not a party to the 1982 United Nations Convention on the Law of the Sea (UNCLOS), the United States generally delineates maritime zones consistent with those established by UNCLOS.

Debate exists regarding whether the United States, as a non-party to UNCLOS, can establish an ECS. According to the Department of State, the United States does not need to be a party to UNCLOS to establish the outer limits of its ECS and exercise its sovereign rights and jurisdiction over this area as provided by UNCLOS Article 76.¹⁵ According to the Department of State, the International Court of Justice concluded that UNCLOS Article 76 is part of customary international law, meaning both party and non-party coastal countries have rights and obligations relating to their continental shelves.¹⁶ Other stakeholders also contend that the United States might be able to establish an ECS without acceding to UNCLOS.¹⁷ However, several witnesses who appeared before the Senate Committee on Foreign Relations during prior hearings on consideration of UNCLOS have stated that U.S. accession to UNCLOS is necessary for the U.S. ECS to be internationally recognized.¹⁸ To date, the Senate has not given advice and consent to accession to UNCLOS.

For more than a century, Congress has shown interest in ocean mapping activities.¹⁹ Congress has directed and funded certain federal departments and agencies to collect relevant data and information about the seafloor beneath and adjacent to U.S. ocean waters because "mapping, exploration, and characterization of the ocean provides basic, essential information to protect and restore the marine environment, stimulate economic activity, and provide security for the United States."²⁰ This report focuses on the mapping activities of the U.S. Extended Continental Shelf Project, a federal initiative that analyzes data to determine the extent of the U.S. ECS. According to the Department of State, the project's work constitutes the largest civilian offshore mapping effort ever conducted by the United States.²¹ The U.S. ECS would be approximately 288,000 nmi² (987,700 square kilometers [km²]),²² or roughly 8% of the total seafloor area beneath the U.S. EEZ. Based on the size of the U.S. ECS, the U.S. Geological Survey (USGS) estimates the energy, mineral, and living resources anticipated to be recovered there may be worth billions to trillions of dollars.²³

The U.S. Extended Continental Shelf Project has analyzed data from areas of the Arctic, Atlantic, Bering Sea, Eastern and Western Gulf of Mexico, Northern Mariana Islands, and Pacific. This report focuses on U.S. ECS areas in the Arctic Ocean, in the Bering Sea, and in the Pacific Ocean offshore the Commonwealth of the Northern Mariana Islands, for several reasons.²⁴ First, projections of shrinking Arctic sea ice cover would presumably increase access to natural resources located on or in the sediments of the seabed.²⁵ Second, both Arctic and non-Arctic countries show increased interest in exploring and developing potential Arctic resources, including in establishing ECS areas or investing in Arctic infrastructure.²⁶ Third, certain areas of the Pacific and Arctic oceans may include natural resources (e.g., critical minerals) that would serve U.S. national security interests.

Determining the Extent of the Continental Shelf

Determining a coastal country's ECS requires knowledge of the geophysical characteristics of the seabed and subsoil.²⁷ The topographic (shape) profile of the seafloor is known as bathymetry. Formulas set forth in UNCLOS to calculate the extent of the continental shelf beyond the 200-nmi limit require precise knowledge of the position of the foot of the continental slope—the point of maximum change in the bathymetric gradient, generally found at the base of the continental slope.²⁸ The position of the foot of the continental slope is coupled with either (1) the thickness of sediments on the seafloor or (2) a fixed distance of 60 nmi from the foot of the continental slope to determine the outer limits of the ECS.²⁹ Different types of data are needed to determine the position of the foot of the continental slope and these two conditions

• Seismic data provide information about the thickness of sediments beneath the seafloor and other characteristics of seafloor sediments.³⁰
• Bathymetric data provide information about the depth of water and profile information about the seafloor to determine the position of the foot of the continental slope.³¹

A coastal country can use one of two formulas described in Article 76 of UNCLOS (or a combination thereof) to maximize the outer limits of its ECS (Figure 2). The first formula is based on the thickness of sediment on the seafloor. To determine the outer limits of the ECS based on this formula, the thickness of the sediment at an outermost fixed point (delineated by a straight line) is at least 1% of the shortest distance from such point to the foot of the continental slope.³² For example, if this formula is applied to a point 100 nmi from the foot of the continental slope, the extent of the ECS could coincide with the point at which the sediment thickness is 1 nmi thick.³³ The second formula is based on distance. It states that the lines delineating the outer limits of the ECS are not to exceed 60 nmi from the foot of the continental slope.³⁴ In the example depicted in Figure 2, the formula based on sediment thickness would maximize the ECS compared with the formula based on the 60 nmi distance. There may be cases where the formula based on distance would maximize the ECS compared to the formula using sediment thickness.

Figure 2. Formulas to Determine the Extended Continental Shelf (according to Article 76 of the United Nations Convention on the Law of the Sea)

Source: Figure modified by the Congressional Research Service. Department of State, "U.S. Extended Continental Shelf Project: About ECS," https://www.state.gov/about-ecs/. Notes: The schematic provides a visual for how the extended continental shelf (ECS) is calculated. The foot of the continental slope is the starting line to determine the ECS. The ECS can be calculated using one of two formulas. Formula 1 (shown in red) extends the continental shelf up to 60 nautical miles seaward of the foot of the continental slope. Formula 2 (shown in green) extends the continental shelf up to a seaward distance where the thickness of the seafloor sediment is at least 1% of the distance to the foot of the continental slope. A coastal country may use either formula (or a combination thereof) to maximize the outer limits of its ECS.

UNCLOS Article 76 provides two constraints for ECS determinations (Figure 3). The first constraint is based on distance. It states that the ECS shall not exceed 350 nmi from the baseline.³⁵ The second constraint is based on water depth. It states that the ECS shall not exceed 100 nmi seaward from the 2,500-meter isobath on the continental shelf.³⁶ If the outer edge of the continental shelf extends past both constraints, a coastal country can use either line to maximize its ECS.

Figure 3. Constraints on the Extent of the Extended Continental Shelf (according to Article 76 of the United Nations Convention on the Law of the Sea)

Source: Figure modified by the Congressional Research Service. Department of State, "U.S. Extended Continental Shelf Project: About ECS," https://www.state.gov/about-ecs/. Notes: m = meters, in reference to water depth. The schematic provides a visual for the two constraints on the extended continental shelf (ECS). A coastal country can use either of the constraint lines to maximize its ECS. Constraint 1 (shown in red) limits the ECS to 350 nautical miles (nmi) from the baseline (i.e., low-water line along the coast). Constraint 2 (shown in green) states that the ECS shall not exceed 100 nmi from the 2,500-m water depth line on the continental shelf (i.e., the isobath).

According to UNCLOS Article 78, a coastal country's rights over its ECS "do not affect the legal status of the superjacent waters,"³⁷ meaning that claiming an ECS does not afford a country control over the waters above it.³⁸

Commission on the Limits of the Continental Shelf

Some coastal countries, including the United States, have pursued efforts to map their ECSs. Under Article 76 of UNCLOS, countries can make a submission to the Commission on the Limits of the Continental Shelf (CLCS) concerning the extent of their continental shelves.³⁹ The CLCS is an independent entity created under UNCLOS that consists of 21 members who are experts in geology, geophysics, or hydrography.⁴⁰ The CLCS does not approve or grant an ECS to coastal countries but makes recommendations to countries on the location of their ECS limits. The limits of the ECS established by a coastal country on the basis of the CLCS recommendations are "final and binding."⁴¹ As of February 2024, more than 60 countries have made submissions to the CLCS.⁴²

Mapping projects are underway by individual countries and through cooperative government studies to support submissions to the CLCS.⁴³ These submissions involve complex scientific investigations, and the CLCS bases its recommendations in part on the provided scientific data and technical analysis. For example, in 2002, the CLCS recommended that Russia provide additional scientific data and information to accompany its 2001 submission with respect to the Arctic Ocean.⁴⁴ In 2015, Russia presented a revised submission to the CLCS.⁴⁵ In June 2023, the CLCS "concluded that it was in a position to efficiently conduct the consideration of [Russia's] submission."⁴⁶

U.S. Extended Continental Shelf Project

Since 2003, the United States has gathered and analyzed geological and geophysical data to determine the extent of its continental shelf through a federal initiative called the U.S. Extended Continental Shelf Project. The project's mission is to "establish the full extent of the U.S. continental shelf, consistent with international law."⁴⁷

The work to determine the outer limits of the U.S. ECS is coordinated by the ECS Task Force, an interagency body of the U.S. government.⁴⁸ The ECS Task Force is chaired by the Department of State, with co-vice chairs from the Department of the Interior (DOI) and NOAA. The Department of State, NOAA, and USGS conduct the majority of work on the project.⁴⁹ According to USGS, these three agencies are "mapping the features of the seafloor and determining sediment thickness to delineate the outer limits of the U.S. ECS using rules set forth in Article 76 of [UNCLOS]."⁵⁰ NOAA leads the U.S. effort to collect bathymetric data and has mapped more than 874,700 nmi² (3 million km²) of the seafloor in support of the U.S. Extended Continental Shelf Project.⁵¹ USGS leads the collection of seismic data for the project.⁵² NOAA's National Centers for Environmental Information (NCEI) stores and makes publicly available all data relevant to the U.S. Extended Continental Shelf Project, including bathymetric, seismic, and geologic sample data.⁵³ Other coastal countries also may access data relevant to the delineation of their ECSs through NCEI's public repository for global bathymetric and seismic data.⁵⁴

On December 19, 2023, the Department of State announced the outer limits of the U.S. ECS as determined by the U.S. Extended Continental Shelf Project.⁵⁵ This announcement accompanied the geographic coordinates defining the outer limits of the U.S. ECS in areas of the Arctic, Atlantic, Bering Sea, Eastern and Western Gulf of Mexico, Northern Mariana Islands, and Pacific (Figure 4),⁵⁶ which went into effect on December 21, 2023.⁵⁷ Both current and former members of the CLCS provided assistance to the United States relating to the analysis and documentation of the U.S. ECS.⁵⁸ According to the Department of State, the United States plans to submit this package to the CLCS upon U.S. accession to UNCLOS but also may consider filing its submission with the CLCS as a non-party to UNCLOS.⁵⁹ If the United States were to file its submission with the CLCS, a review of the U.S. ECS would take place at some future date given the length of the submission queue, which the CLCS reviews in order of receipt.⁶⁰

The following sections of the report examine data collected in support of the U.S. Extended Continental Shelf Project in areas offshore U.S.-affiliated Pacific islands (Guam and the Commonwealth of the Northern Mariana Islands), as well as in areas offshore Alaska in the Arctic and Bering Sea.

Figure 4. Seven Regions of the U.S. Extended Continental Shelf (as determined by the U.S. Extended Continental Shelf Project)

Source: Map modified by the Congressional Research Service. Department of State, "The U.S. ECS," December 19, 2023, https://www.state.gov/the-us-ecs/. Notes: Areas of the U.S. extended continental shelf (ECS) identified by the U.S. Extended Continental Shelf Project, a federal initiative that aims to establish the full extent of the U.S. ECS according to international law (i.e., in alignment with Article 76 of the United Nations Convention on the Law of the Sea). Red lines represent the outer limits of the U.S. ECS, and red shaded areas delineate the U.S. ECS beyond the 200 nautical mile (nmi) limit of the continental shelf (thin dark lines), representing 288,000 square nmi (987,700 square kilometers). Portions of the U.S. ECS are bounded by previously established maritime boundaries with neighboring countries (i.e., Cuba, Mexico, and Russia). Other portions may overlap with ECS areas of other neighboring countries (i.e., the Bahamas, Canada, and Japan).

U.S. Extended Continental Shelf Project Activities Offshore U.S.-Affiliated Pacific Islands

The U.S. Extended Continental Shelf Project identified 379 nmi² (1,300 km²) of the U.S. ECS located northeast of the Northern Mariana Islands that it claims to be a prolongation of the U.S. land masses of the island system (Figure 4).⁶¹ This area was delineated using the 60 nmi distance formula and the distance constraint (see "Determining the Extent of the Continental Shelf," above).⁶² In addition, a portion of the U.S. ECS is bounded by Japan to the north.⁶³ According to the Department of State, "the United States and Japan have not concluded a boundary treaty delimiting the continental shelf in this region."⁶⁴

U.S. Extended Continental Shelf Project Activities in the Arctic

A strategic objective of the 2022 National Strategy for the Arctic Region is for the United States to "delineate the outer limits of the U.S. continental shelf in accordance with international law."⁶⁵ The U.S. Extended Continental Shelf Project identified 151,700 nmi² (520,400 km²) of the U.S. ECS in the Arctic that it claims to be a prolongation of the land mass of Alaska (Figure 4).⁶⁶ The U.S. ECS in the Arctic represents 53% of the total U.S. ECS. The U.S. Extended Continental Shelf Project used a combination of the sediment thickness and 60 nmi formulas and both the distance and depth constraints to delineate the outer limits of the U.S. ECS in this region (see "Determining the Extent of the Continental Shelf," above).⁶⁷ In addition, portions of the U.S. ECS are bounded by Canada to the east and Russia to the west.⁶⁸ The United States and Canada do not have a maritime boundary agreement in the Arctic. However, according to the Department of State, "Canada has advised the United States that it would not object to the consideration of a U.S. submission by the [CLCS], without prejudice both to the delineation of the outer limits of its own continental shelf and to the matters relating to the delimitation of boundaries in this region between the United States and Canada."⁶⁹ In 1990, Russia (then the Soviet Union) and the United States agreed to a maritime boundary to address overlapping ECS areas in the Arctic.⁷⁰ To date, Russia has not asserted ECS claims in any areas that might be considered part of the U.S. ECS.⁷¹

The U.S. Extended Continental Shelf Project also identified 51,400 nmi² (176,300 km²) of the U.S. ECS located in the Bering Sea that it claims to be a prolongation of the land mass of Alaska and the Aleutian Islands (Figure 4).⁷² The U.S. Extended Continental Shelf Project used a combination of the sediment thickness and 60 nmi formulas and the distance constraint to delineate the outer limits of the U.S. ECS in this region.⁷³ In addition, the northwest portion of the U.S. ECS in this area is bounded by the 1990 U.S.-Russia maritime boundary.⁷⁴ The U.S. Extended Continental Shelf Project further reports that the U.S. ECS, based on the sediment thickness and 60 nmi distance formulas, extends beyond the previously agreed-upon maritime boundary between the United States and Russia.⁷⁵

Issues for Congress

Knowledge of the limits of a coastal country's continental shelf allows the country to declare to other countries the exact extent of its ECS and the sovereign rights it is entitled to exercise within that area.⁷⁶ Some stakeholders contend that the U.S. ability to exercise sovereign rights over its ECS is key to ensuring U.S. economic prosperity and national security.⁷⁷

Efforts by the United States to map its potential ECS may serve at least two purposes. First, ECS data may help identify likely "resource-rich realms,"⁷⁸ thereby providing federal agencies with the opportunity to manage, conserve, explore, and exploit the resources of the seabed and subsoil contained within these areas.⁷⁹ Second, ECS data may elucidate maritime boundaries between the United States and a neighboring country. Established maritime boundaries with neighboring countries may be necessary to exercise sovereign rights over the U.S. ECS.

In the 112^th Congress, the Senate Committee on Foreign Relations (Committee) held three hearings on UNCLOS and took no further action.⁸⁰ UNCLOS has since remained with the committee. The U.S. Extended Continental Shelf Project's work to document the seven regions with U.S. ECS provides new information for the committee and other Members of Congress to consider in their deliberation of UNCLOS.

U.S. Accession to UNCLOS

One common argument for U.S. accession to UNCLOS is that, as a party to the convention, the United States could access the CLCS's procedures for according international recognition and legal weight to the U.S. ECS.⁸¹ A recommendation from the CLCS on the U.S. ECS would be final and binding.⁸² In the 118^th Congress, S.Res. 466 identifies that "lack of full-party membership to UNCLOS limits the access and influence of the United States to critical territorial dispute management, including matters involving pursuit and competition of extended outer continental shelf submissions" and relying on customary international norms is "not sufficient."

According to the Department of State, the United States is "open to filing its submission with the Commission as a non-party" to UNCLOS.⁸³ It remains unclear if the CLCS would consider a U.S. submission in these circumstances.⁸⁴ Further, it remains unclear how the international community would respond to such a U.S. submission. One source reports objections from Russia, with a member of the Russian Federation Council quoted as saying, "the Americans act without any international legal basis at all, which means the international community has every right not to recognize new borders."⁸⁵ A second source quoted the Chair of Russia's Ministry for the Development of the Russian Far East and Arctic as saying, "the unilateral expansion of boarders in the Arctic is unacceptable and can only lead to increased tensions," in reference to the U.S. ECS announcement.⁸⁶

In some instances, the United States has exercised sovereign rights over natural resources in areas of its ECS without being a party to UNCLOS. For example, DOI has offered the westernmost ECS area of the Gulf of Mexico, commonly known as the Western Gap, for oil and gas development (see Figure 4).⁸⁷ Some stakeholders reference DOI's leases in the Western Gap as examples to refute the claim that U.S. accession to UNCLOS is necessary for the United States to exercise sovereign rights over the natural resources of the seabed and subsoil.⁸⁸ The United States has exercised sovereign rights over the natural resources in the Western Gap without objection from the international community; however, the United States has not exercised sovereign rights over the natural resources located in areas of the U.S. ECS without agreed-upon maritime boundary with a neighboring country (see "Delimitation of and Disputes over Maritime Boundaries," below). Similarly, the United States has not exercised sovereign rights in an area of the U.S. ECS adjacent to the Area (i.e., areas beyond national jurisdiction).⁸⁹

U.S. Extended Continental Shelf Areas with Potential Resources

The extent of scientific evidence has been a factor underpinning ECS claims. Countries have contested ECS claims, citing insufficient scientific data as the reason for their objection.⁹⁰ Congress may consider providing resources to U.S. agencies (e.g., the Department of State, NOAA, USGS) for additional research and data collection to counter other countries' objections on these grounds.⁹¹ The U.S. Extended Continental Shelf Project reports that 37 separate cruises collected bathymetric data for the project, totaling nearly 2.5 years of sea time.⁹² According to NOAA, while research cruises were collecting bathymetric data for the U.S. Extended Continental Shelf Project, the agency spent approximately $52 million (in non-inflation adjusted funding) on these cruises and their staffing support and to fund the project office.⁹³ Since 2018, NOAA has spent approximately $800,000 per year on management and analysis of these bathymetric data.⁹⁴

The ECS delineated by the U.S. Extended Continental Shelf Project may protect future U.S. economic opportunities.⁹⁵ Because an ECS falls under national jurisdiction, activities such as seabed mining of hardrock minerals on the ECS would be subject to domestic regulations. The International Seabed Authority (ISA), an autonomous organization established by UNCLOS, regulates all seabed mining activities taking place under the high seas, including the approval of exploration and exploitation contracts to public and private mining enterprises, provided they are sponsored by a country party to UNCLOS.⁹⁶ An established ECS would prohibit foreign countries from pursuing exploration or exploitation contracts through the ISA for areas located within another country's ECS. In addition, an extension of the outer limits of the U.S. ECS to include mineral-rich areas would be a potential strategy to access mineral resources under sole U.S. authority, rather than under the authority of the ISA. Available technology, among other factors, currently limits the exploitation of seabed resources; however, some countries show increasing interest in the exploration of seabed minerals.⁹⁷

A secure domestic supply of seabed minerals of national strategic importance (i.e., critical minerals) located in areas of the U.S. ECS could reduce U.S. dependence on foreign countries, in particular China, for these resources.⁹⁸ For example, certain areas of the central and northwest Pacific Ocean have mineral deposits (polymetallic nodules) or crusts that are rich in cobalt, manganese, and other critical minerals.⁹⁹ The U.S. ECS located northeast of the Northern Mariana Islands represents 0.01% of the total U.S. EEZ.¹⁰⁰ Congress may be interested in whether any of the data collected by the U.S. Extended Continental Shelf Project in areas offshore Hawaii and U.S. island territories in the Pacific may support additional U.S. ECS areas, particularly areas that may contain abundant mineral resources (Figure 5).

Figure 5. Selected Cruise Surveys That Collected Extended Continental Shelf Data Offshore Hawaii and U.S.-Affiliated Pacific Islands

Source: Congressional Research Service (CRS), using cruise survey data provided to CRS by the National Oceanic and Atmospheric Administration's (NOAA's) National Centers for Environmental Information (NCEI) on August 3, 2023, and U.S. extended continental shelf (ECS) boundaries published by the Department of State (see "U.S. Extended Continental Shelf," https://www.state.gov/the-us-ecs/). The exclusive economic zone (EEZ) boundaries were derived from the Sovereign Limits database (sovereignlimits.com). Notes: The map shows four of the five cruise surveys that collected data used for the U.S. Extended Continental Shelf Project (orange) and seven of the nine cruise surveys that NOAA considers possibly relevant to the U.S. ECS (green; NOAA, NCEI, "U.S. Extended Continental Shelf Data," https://www.ncei.noaa.gov/products/us-extended-continental-shelf-data). Thin blue lines denote the 200-nautical mile EEZ of coastal countries. CRS was unable to obtain data for three cruises; CRS requested these files from NCEI on December 6, 2023.

The establishment of the U.S. ECS in the Arctic and the ECS of other Arctic coastal countries could signal to non-Arctic countries (e.g., China¹⁰¹) that existing and potential Arctic resources are under the legal jurisdiction of the five Arctic coastal nations.¹⁰² In the Arctic Ocean, USGS scientists have estimated undiscovered conventional oil and gas resources,¹⁰³ and have identified high concentrations of critical minerals in seafloor deposits sampled more than 300 nmi north of Alaska.¹⁰⁴ USGS scientists also are studying ECS data to better understand the distribution of gas hydrates, a potentially valuable energy resource, in the Bering Sea.¹⁰⁵ The U.S. ECS in the Arctic and Bering Sea combined represents 6% of the U.S. EEZ.¹⁰⁶ Canada, Denmark (for Greenland), Norway, and Russia have each made at least one submission to the CLCS.¹⁰⁷ The majority of the Arctic seabed is under the national jurisdictions of the five Arctic coastal countries.¹⁰⁸ In August 2023, the CLCS provided Russia with recommendations relating to its 2001 (and 2015 revised) ECS submission related to the Arctic Ocean.¹⁰⁹ These recommendations may help secure Russia's legal rights to resources across a portion of the Arctic's seafloor.¹¹⁰

Resources identified in portions of the U.S. ECS could add to current resources of U.S. supplies of critical minerals and other commodities. Should the United States wish to exercise sovereign rights over the natural resources located on the U.S. ECS, Congress may consider several potential issues. An ECS in the seven regions identified by the U.S. Extended Continental Shelf Project would increase the area of continental shelf under U.S. jurisdiction by approximately 288,000 nmi² (987,700 km²), roughly 8% of the total seafloor area beneath the U.S. EEZ.¹¹¹ This increase in submerged land may necessitate additional resources for the DOI, which has jurisdiction over the submerged lands of the U.S. outer continental shelf (OCS) for energy development,¹¹² and for NOAA's National Marine Fisheries Service, which has authority over the management of bottom-dwelling marine organisms living on or in the sediments of the U.S. OCS.¹¹³ In addition, the exploitation of resources from U.S. ECS areas could increase federal revenues. For example, the exploitation of oil, gas, hydrogen, or seabed minerals on the U.S. ECS could generate revenues flowing to the federal government from lease sales, royalties on production, and rental fees.¹¹⁴ Congress may consider this possibility when evaluating federal revenue and royalty policies, which could also affect federal policies for sharing these potentially new sources of federal revenues with coastal states.¹¹⁵

Delimitation of and Disputes over Maritime Boundaries

Only a country with rights and standing can challenge an ECS backed by geological and geophysical data, as required by Article 76 of UNCLOS. Disputes over maritime boundaries must be resolved between the countries involved in the disagreement. Although the CLCS can work to delineate ECS areas, it has no mechanism for resolving international disputes.¹¹⁶

The United States has agreed to maritime boundaries that include areas of the U.S. ECS in bilateral agreements with Cuba, Mexico, and Russia,¹¹⁷ (the 1990 U.S.-Russia maritime boundary is discussed in "U.S. Extended Continental Shelf Project Activities in the Arctic," above). In 2000, the United States and Mexico signed a treaty (commonly known as the Western Gap Treaty) delimiting the areas of their ECS in the Gulf of Mexico.¹¹⁸ Following the Senate's consent to ratification of this treaty, the United States has exercised sovereign rights over the natural resources in its ECS in the Western Gap.¹¹⁹

On December 18, 2023, President Biden transmitted two bilateral maritime treaties—one for Mexico and one for Cuba—to the Senate for advice and consent.¹²⁰ Both of these bilateral treaties delineate maritime boundaries of an area of the ECS in the Eastern Gulf of Mexico, commonly known as the Eastern Gap.¹²¹ The two U.S. ECS areas in the Gulf of Mexico established by the U.S. Extended Continental Shelf Project are bounded by maritime boundaries described in the bilateral treaties.¹²²

Some areas of the U.S. ECS have unresolved maritime boundaries with neighboring countries. To resolve them, the United States and a neighboring country must first agree to a maritime boundary, after which the President would transmit that agreement to the Senate for its advice and consent. For example, in the Arctic, the U.S. ECS overlaps with ECS areas of Canada.¹²³ Both countries worked cooperatively to collect data needed to delineate the ECS in a two-ship operation involving the U.S. Coast Guard Cutter Healy and the Canadian Coast Guard ship Louis S. Saint Laurent.¹²⁴ According to the Department of State, this type of scientific and diplomatic cooperation has "saved millions of dollars for both countries, provided data both countries need, ensured that data are collected only once in the same area, and increased scientific and diplomatic cooperation."¹²⁵

The United States and Canada also have unresolved ECS boundaries in the Atlantic.¹²⁶ The United States and the Bahamas have unresolved ECS boundaries in the Atlantic, as well.¹²⁷

In the Pacific, the United States has unresolved maritime boundaries with Japan. The U.S. ECS (by way of the Northern Mariana Islands) overlaps with ECS areas of Japan in its Ogasawara Plateau Region,¹²⁸ an area Japan reportedly may be exploring for potential resources.¹²⁹ According to the Department of State, the United States and Japan have consulted on overlapping areas of the ECS in this region of the Pacific.¹³⁰

Implications for UNCLOS

The U.S. Extended Continental Shelf Project provides Congress with a new information to weigh in its potential deliberation of U.S. accession to UNCLOS. A month prior to the Department of State's December 19, 2023, announcement of the U.S. ECS, Senators introduced S.Res. 466, which "urge[d] the United States Senate to give its advice and consent to the ratification of the UNCLOS." Other Members of Congress considering seabed mining options wrote a letter to Secretary of Defense Lloyd Austin on December 7, 2023, calling on the Department to "explore every avenue to strengthen our rare earth and critical minerals supply chains."¹³¹ The letter invokes the participation of the United States as an observer state in the ISA, but does not explicitly mention the option of U.S. accession to UNCLOS.¹³²