Ross Sea

The Ross Sea is a deep bay of the Southern Ocean in Antarctica, lying roughly between Victoria Land to the west and Marie Byrd Land to the east, and bounded to the south by the Ross Ice Shelf — the world's largest ice shelf. Covering approximately 637,000 km², the Ross Sea occupies the Pacific sector of the Southern Ocean at latitudes between approximately 60°S and 85°S, reaching further south than any other ocean on Earth and providing the most accessible sea route to the geographic South Pole. At its centre lies the coordinate 76°S 175°W, placing it on the exact opposite side of the planet from the heavily populated northern latitudes most mariners call home.

Unlike virtually every other sea on Earth, the Ross Sea has no commercial ports, no regular shipping routes, and no permanent civilian population. Its shores and the ice shelves that dominate its southern boundary are part of Antarctica — a continent governed collectively under the Antarctic Treaty System (the 1959 Antarctic Treaty and its associated agreements) rather than by any sovereign state. The nearest inhabited year-round communities are at McMurdo Station, operated by the United States Antarctic Program (USAP), and Scott Base, operated by Antarctica New Zealand — both research stations on Ross Island at the southwestern corner of the sea.

What makes the Ross Sea globally significant — despite its remoteness and inaccessibility — is the extraordinary quality of its marine ecosystem and its outsized role in regulating the Earth's climate. Scientists consistently describe it as the world's most intact large marine ecosystem: the only ocean region of comparable scale where the food web from phytoplankton to top predators has not been fundamentally altered by industrial fishing, pollution, or habitat destruction. It is the primary production site of Antarctic Bottom Water (AABW) — the densest water mass on Earth, which sinks to the ocean floor and drives the deep limb of global thermohaline circulation. And it is protected since 2017 by the world's largest Marine Protected Area, covering 1.55 million km² of the Southern Ocean.

For deck officers and maritime professionals who may be called upon to operate in Antarctic waters — aboard scientific resupply vessels, fisheries patrol ships, or expedition tourism vessels — the Ross Sea presents a navigation environment of extreme challenge and genuine danger. The IMO Polar Code (mandatory since January 2017) establishes minimum requirements for vessels operating in polar waters, and NAVAREA XIV (coordinated by New Zealand) provides the framework for navigational warnings and communications. This guide covers the geography, oceanography, ecology, history, and navigation safety considerations of one of the most remote and consequential bodies of water on Earth.

1. Geography & Physical Characteristics

The Ross Sea is bounded to the west by the Victoria Land coastline — a rugged, mountainous Antarctic coast forming part of the Transantarctic Mountains — and to the east by the less well-defined coast of Marie Byrd Land, which is the largest unclaimed territory on Earth (no nation has asserted sovereignty over it, even under the Antarctic Treaty framework). To the south, the sea terminates at the sheer blue-white cliffs of the Ross Ice Shelf, which James Clark Ross called the “Great Ice Barrier” when he first encountered it in 1841 and which stretches for some 600 km along the sea's southern boundary.

The Ross Ice Shelf is the world's largest ice shelf — a permanent, floating platform of glacial ice covering approximately 487,000 km², roughly the size of France. Fed by ice streams flowing from both the West Antarctic Ice Sheet and the East Antarctic Ice Sheet, the shelf ranges from approximately 100 metres thick at its seaward margin to more than 1,000 metres at its grounding line where it rests on the underlying bedrock. The ice cliffs at the shelf front tower 15 to 50 metres above sea level and represent an absolute navigational barrier — no vessel can proceed further south. Periodic calving of enormous tabular icebergs from the Ross Ice Shelf produces some of the largest free-floating objects ever observed. Iceberg B-15, which calved in March 2000, measured 295 by 37 km — larger than the island of Jamaica — and temporarily disrupted resupply to McMurdo Station by blocking McMurdo Sound.

Ross Island, located at the southwestern corner of the sea where McMurdo Sound meets the ice shelf, is one of the most geologically remarkable islands on Earth. It is dominated by Mount Erebus (3,794 m), the world's southernmost active volcano, which maintains a persistent lava lake in its summit crater and releases volcanic gases and ice crystals continuously. Mount Terror (3,230 m) is an adjacent extinct volcano. Ross Island is connected to the Ross Ice Shelf by sea ice in winter and is the site of McMurdo Station (USA) and Scott Base (NZ), as well as the historic huts of Robert Falcon Scott's expeditions at Cape Evans and Hut Point, and of Ernest Shackleton's Nimrod expedition at Cape Royds. Cape Crozier, at the eastern tip of Ross Island, is home to the world's largest Emperor penguin colony.

Roosevelt Island is a large, ice-covered island embedded within the eastern Ross Ice Shelf, approximately 200 km east of the shelf front. It is surrounded by and partly covered by the ice shelf and is of significant glaciological interest as an independent ice dome that may help stabilise the surrounding ice shelf. The Bay of Whales — a natural embayment in the Ross Ice Shelf east of Roosevelt Island — was a critical location in the history of Antarctic exploration. It provided a more southerly starting point for sledge journeys than any other navigable point in the Ross Sea, and Roald Amundsen used it as the base camp (Framheim) for his successful 1911 South Pole expedition. The Bay of Whales no longer exists in a fixed sense; the calving of successive tabular icebergs has altered the geometry of the ice shelf front periodically over the decades.

The bathymetry of the Ross Sea is characterised by a broad continental shelf — one of the widest in the world at approximately 500–800 km — overlying which average depths are relatively modest (less than 500 m in many areas). The deeper central and northern Ross Sea reaches average depths of 2,431 m, with the maximum depth of 4,200 m recorded in the northern portions of the sea where the continental shelf descends to the deep Southern Ocean floor. The enormous volume of glacial meltwater and brine from sea ice formation gives the Ross Sea its characteristic oceanographic properties.

2. Oceanography & Polar Climate

The Ross Sea plays a role in global ocean circulation that is entirely disproportionate to its geographical size. It is one of the primary formation sites on Earth for Antarctic Bottom Water (AABW) — the densest water mass in the global ocean and the driver of the deep limb of the thermohaline circulation (the “global ocean conveyor belt”). During the Antarctic winter, temperatures on the Ross Ice Shelf can fall below -40°C. These extreme temperatures cool the surface waters of the Ross Sea to the point where sea ice forms. As ice crystalises, brine is rejected into the surrounding water, increasing its salinity and therefore its density. The combination of extreme cold and elevated salinity produces High Salinity Shelf Water (HSSW) dense enough to sink to the ocean floor, flowing off the continental shelf and down the slope to become Antarctic Bottom Water, which then spreads northward along the bottom of all three ocean basins — the Pacific, Atlantic, and Indian Oceans — over a timescale of centuries.

A critical feature enabling this AABW production is the Ross Sea Polynya — the largest coastal polynya in Antarctica. A polynya is a persistent area of open water surrounded by sea ice, maintained by the action of strong katabatic winds blowing off the continental ice sheet. In the Ross Sea, these cold, dry, dense winds blow persistently from the south and southwest, driving newly formed sea ice northward and away from the coast, preventing ice accumulation in the polynya area and exposing the ocean surface to continued cooling. The Ross Sea Polynya covers up to 300,000 km² in summer — an area comparable to Italy — and is the engine of both AABW production and the extraordinary biological productivity that characterises the Ross Sea ecosystem. Phytoplankton blooms in the polynya are among the most intense on Earth.

Sea ice extent in the Ross Sea shows extreme seasonality. In winter (June–August), virtually the entire sea is covered by pack ice extending well north of 60°S. In summer (December–February), the southern advance of the ice edge retreats to approximately 75°S in the western Ross Sea and to the ice shelf front further east, opening a navigable — though heavily ice-laden — corridor to McMurdo Sound. The sea ice in the Ross Sea consists of a mixture of first-year ice (formed in the current winter) and multi-year ice (surviving from previous seasons), with pressure ridges, hummocks, and embedded bergy bits presenting serious hazards to all but purpose-built icebreakers.

The climate of the Ross Sea is one of the harshest on Earth. Katabatic winds — gravity-driven flows of cold, dense air descending from the Antarctic plateau — can reach hurricane force (above 64 knots) with little warning, particularly in McMurdo Sound and along the Victoria Land coast. Mean winter temperatures at Ross Island are approximately -25°C, falling to below -50°C during the most severe outbreaks. Summer temperatures rarely exceed -5°C near the ice shelf and may reach 0 to +3°C in the open northern Ross Sea during calm periods. Blizzards with near-zero visibility can develop within hours, trapping personnel outside in life-threatening conditions. The combination of cold temperatures, wind chill, and sea spray makes exposure on deck during polar operations an extreme cold injury risk.

3. Marine Ecology & Biodiversity

The Ross Sea is described by marine scientists as the world's most intact large marine ecosystem — the last ocean region of its scale where the complete food web, from phytoplankton at the base to apex predators at the top, functions essentially without significant human disruption. This status is a direct consequence of its remoteness and the relative brevity of commercial fishing in its waters before protective measures were introduced. The comparison with other ocean ecosystems — even those formally protected — is stark: in almost every other large marine ecosystem on Earth, industrial fishing has fundamentally restructured food web dynamics and depleted target species. In the Ross Sea, that restructuring has not yet occurred at comparable scale.

At the apex of the Ross Sea food web are several charismatic and ecologically significant species. Emperor penguins (Aptenodytes forsteri) — the world's largest penguin species, standing approximately 1.1 metres tall and weighing up to 45 kg — breed on the fast sea ice around Ross Island. The colony at Cape Washington on the Victoria Land coast is one of the largest Emperor penguin colonies in the world, with approximately 25,000 breeding pairs. The colony at Cape Crozier on the eastern tip of Ross Island was the subject of the famous winter journey undertaken by Edward Wilson, Henry Bowers, and Apsley Cherry-Garrard in the darkness of the 1911 Antarctic winter to collect Emperor penguin eggs for embryological research — chronicled in Cherry-Garrard's The Worst Journey in the World (1922). Emperor penguins breed in winter on the sea ice, enduring temperatures of -60°C and winds of 200 km/h to incubate their eggs.

Weddell seals (Leptonychotes weddellii) are the world's most southerly breeding mammal, maintaining breathing holes through the fast ice with their teeth and capable of diving to 600 metres depth for up to 80 minutes. Large colonies haul out on the sea ice around Ross Island and are a familiar sight near McMurdo Station, where they have been the subject of long-term physiological research programmes. Orca (killer whales) of the Type C ecotype — found only in the Ross Sea — are the smallest ecotype of killer whale, specialising in hunting Antarctic toothfish under the sea ice in a behaviour unique among the world's orca populations.

Antarctic toothfish (Dissostichus mawsoni), known commercially as Patagonian sea bass or Chilean sea bass in international markets, is the apex fish predator of the Ross Sea ecosystem. A slow-growing, long-lived species (up to 50 years, reaching 2 metres length and 150 kg), it inhabits depths of 1,500–2,200 m and is a primary prey item of Weddell seals and Type C orcas. Before the establishment of the Ross Sea MPA, it was the target of a controversial longline fishery. Antarctic silverfish (Pleuragramma antarctica) is the keystone species of the Ross Sea — the principal prey item linking the primary productivity of the phytoplankton bloom to penguins, seals, and orcas. Crystal krill(Euphausia crystallorophias), also called ice krill, is the dominant krill species in the Ross Sea polynya and a critical prey item for silverfish, penguins, and baleen whales.

4. Maritime Routes & Scientific Resupply

The Ross Sea has no commercial shipping routes. There are no ports, no scheduled freight services, no tanker routes, and no container operations. All maritime activity in the Ross Sea is either scientific resupply, government-operated fisheries patrol, or expedition tourism — the last subject to strict regulation under Antarctic Treaty instruments and the IMO Polar Code. For deck officers, the Ross Sea represents a navigation environment fundamentally unlike any other: one governed by scientific mission requirements, extreme environmental constraints, and an almost complete absence of the maritime infrastructure (aids to navigation, port services, search and rescue resources, towage, bunkering) that is taken for granted in every other part of the world.

The primary maritime activity in the Ross Sea is annual scientific resupply to the research stations. The United States Antarctic Program (USAP) conducts Operation Deep Freeze — the annual logistics mission to McMurdo Station and South Pole Station — using vessels assigned by Military Sealift Command (MSC). A typical Operation Deep Freeze season involves a US Coast Guard icebreaker (USCGC Polar Star, WAGB-10, or its successor) breaking a channel through the fast ice in McMurdo Sound from December onward, followed by a fuel tanker (to replenish McMurdo's winter fuel supply) and a cargo vessel delivering bulk supplies, vehicles, equipment, and food for the following year. The logistics hub for USAP is Christchurch, New Zealand(Port of Lyttelton), from which both sea and air resupply operations depart. A secondary staging point is Hobart, Tasmania, Australia, also used by the Australian Antarctic Division.

New Zealand's Scott Base is resupplied by the RV Tangaroa or chartered vessels from Port Lyttelton, Christchurch. Italy's Mario Zucchelli Station (formerly Terra Nova Bay Station) is served by the research vessel OGS Explora or chartered polar vessels operating from Lyttelton. South Korea's Jang Bogo Station (opened 2014, Terra Nova Bay) is supported by the icebreaker RV ARAON, South Korea's sole polar research vessel, which departs from Incheon, South Korea.

Antarctic tourism to the Ross Sea is a small but growing activity. Expedition cruise vessels — typically of between 100 and 200 passengers, operating as purpose-built Polar Class ice-strengthened ships — make voyages to the Ross Sea from Bluff (Invercargill), New Zealand, in the December–February summer season. These itineraries visit Cape Royds and Cape Evans (Scott's historic huts), Cape Crozier (Emperor penguin colony), the Bay of Whales area, and, if ice permits, McMurdo Sound. All expedition vessels operating south of 60°S are subject to the IMO Polar Code and to the Antarctic Treaty's Environmental Protocol requirements, including a ban on heavy fuel oil (HFO) in Antarctic Treaty Area waters (which entered into force progressively from 2024). The Ross Sea MPA, established in 2017, covers 1.55 million km² — the world's largest Marine Protected Area — and prohibits commercial fishing across most of the Ross Sea, with limited scientific fishing permitted in a designated Special Research Zone.

5. Polar Research Stations

The Ross Sea region hosts the highest concentration of Antarctic research stations of any part of the continent. Their location in the most accessible part of Antarctica relative to New Zealand and Australia, and the area's scientific importance, have made the Ross Sea the hub of Antarctic scientific operations since the International Geophysical Year (1957–58).

McMurdo Station (USAMS) — United States

McMurdo Station, operated by the United States Antarctic Program (USAP) under the management of the National Science Foundation, is the largest Antarctic station and the logistical hub of all US Antarctic operations. Located on the southern tip of Ross Island at Hut Point Peninsula, McMurdo is a small town by Antarctic standards: at peak summer population (December–February) it accommodates approximately 1,000 people — scientists, support staff, engineers, and logistics personnel. Winter population drops to approximately 150. McMurdo has more than 100 buildings, a harbour (Winter Quarters Bay), a helicopter pad, and road connections to nearby Williams Field (skiway) and Phoenix Airfield (on the sea ice or shelf ice). It has a seawater desalination plant, a power plant, a medical clinic, a firehouse, a dormitory, shops, a bar, and the full logistical infrastructure of a small Antarctic town. Vessels approaching McMurdo must transit the icebreaker channel cut through McMurdo Sound fast ice — typically 2–3 metres thick — and anchor in Winter Quarters Bay. VHF communications with McMurdo are maintained on standard maritime and USAP-specific channels.

Scott Base (NZSCB) — New Zealand

Scott Base, operated by Antarctica New Zealand, is located approximately 3 km from McMurdo Station on the opposite side of Hut Point Peninsula, on the edge of the Ross Ice Shelf. It is a much smaller facility — a cluster of approximately ten interconnected buildings painted in New Zealand's characteristic “Scott Base green” — accommodating up to approximately 85 people in summer. Scott Base is the operational and logistical base for all New Zealand scientific activities in Antarctica and maintains close cooperation with McMurdo. It is serviced by the same icebreaker channel and McMurdo Sound approach. New Zealand has committed to a full rebuild of Scott Base, with construction of a new, environmentally sustainable station underway in the early 2020s.

Mario Zucchelli Station — Italy

The Mario Zucchelli Station (MZS, formerly Terra Nova Bay Station), operated by the Italian National Antarctic Research Programme (PNRA), is a summer-only station located at Terra Nova Bay on the Victoria Land coast, approximately 350 km north of McMurdo. It accommodates up to approximately 80 scientists and support staff in summer and is serviced by sea from the research vessel OGS Explora. Terra Nova Bay benefits from a persistent coastal polynya — the Terra Nova Bay Polynya — which keeps the immediate vicinity ice-free for longer periods than surrounding areas, facilitating vessel access. The station includes meteorological, geophysical, and biological research laboratories.

Jang Bogo Station — South Korea

Jang Bogo Station, opened in February 2014 and operated by the Korea Polar Research Institute (KOPRI), is located at Terra Nova Bay, approximately 3 km from the Italian Mario Zucchelli Station. It is South Korea's second Antarctic research station (the first being King Sejong Station on the Antarctic Peninsula). Jang Bogo can accommodate up to 60 people in summer and maintains a small year-round winter presence. It is serviced by the Korean icebreaker RV ARAON, which also conducts oceanographic research voyages throughout the Southern Ocean.

6. Historical & Exploration Significance

The recorded history of the Ross Sea begins with the British Antarctic Expeditionof 1839–1843 under Captain James Clark Ross RN. Ross, already celebrated for locating the North Magnetic Pole in 1831, led HMS Erebus and HMS Terror south from Hobart, Tasmania in January 1841. Breaking through the pack ice, Ross discovered the sea that now bears his name — a vast, open embayment in the Antarctic continent that gave him access much further south than any previous navigator. He discovered and named Victoria Land, Ross Island, Mount Erebus and Mount Terror (naming them after his ships), and encountered the southern boundary of the sea — the immense ice cliff he called the “Great Ice Barrier” (now the Ross Ice Shelf). Ross reached 78°10'S, a furthest-south record that stood for nearly sixty years. His two vessels were wooden, unstrengthened sailing ships — their ability to navigate Antarctic pack ice in 1841 remains one of the remarkable seamanship achievements in maritime history.

The Ross Sea became the principal gateway to the South Pole during the Heroic Age of Antarctic Exploration (1897–1922). Ernest Shackleton's Nimrod Expedition (1907–09) operated from a base at Cape Royds on Ross Island, from which Shackleton's party reached 88°23'S — within 180 km of the South Pole — before being forced to turn back. Robert Falcon Scott's Terra Nova Expedition (1910–13) established base camp at Cape Evans, Ross Island. Scott's polar party of five reached the South Pole on 17 January 1912, only to discover that Roald Amundsen had beaten them by 33 days. Scott and his four companions — Wilson, Bowers, Oates, and Evans — all perished on the return journey. Their bodies were found in November 1912 by a search party from Cape Evans, only 18 km from the One Ton Depot they had been unable to reach.

Roald Amundsen's Fram Expedition used the Bay of Whaleson the eastern Ross Ice Shelf as the base camp for his rival South Pole bid. By starting from the Bay of Whales rather than Ross Island, Amundsen gained approximately 100 km advantage over Scott. Amundsen's party of five reached the South Pole on 14 December 1911, using dog sledges and a systematic depot-laying strategy that proved decisive. His use of the Ross Ice Shelf and the Bay of Whales as his Antarctic highway demonstrates the critical role the sea played in the race to the pole.

The modern era of Ross Sea maritime operations began with Operation Highjump(1946–47) — a massive US Navy expedition involving 4,700 personnel, 13 ships, and 33 aircraft under Rear Admiral Richard E. Byrd. This was followed by Operation Deep Freeze, begun in 1955 in preparation for the International Geophysical Year (1957–58) and continuing as an annual US Antarctic resupply mission to the present day. The Antarctic Treaty, signed on 1 December 1959 and entering into force on 23 June 1961, established Antarctica as a continent devoted to peaceful scientific cooperation, prohibiting military activities, nuclear testing, and mineral resource exploitation. The Treaty has 54 signatories and 29 consultative parties. The Protocol on Environmental Protection (the Madrid Protocol, 1991) further designated Antarctica as a “natural reserve devoted to peace and science” and imposed a comprehensive ban on mineral resource activities.

7. Navigation Safety & Polar Hazards

The Ross Sea falls within NAVAREA XIV (Antarctic — New Zealand Sector), one of the 21 global navigational warning areas under the IMO/IHO World-Wide Navigational Warning Service (WWNWS). NAVAREA XIV is coordinated by the Royal New Zealand Navy and covers the Antarctic waters of the Pacific and Indian Ocean sectors south of 60°S. Given the near-total absence of NAVTEX transmitter infrastructure in Antarctic waters, navigational warnings for NAVAREA XIV are broadcast primarily via SafetyNET on Inmarsat-C, supplemented by information from the US National Ice Center (USNIC), the Australian Antarctic Division, and the New Zealand Meteorological Service. All vessels transiting to the Ross Sea should maintain a continuous Inmarsat-C watch and subscribe to NAVAREA XIV Enhanced Group Call (EGC) broadcasts. HF (high frequency) radio communications are usable but highly variable at Ross Sea latitudes due to ionospheric conditions, and satellite communications are significantly reduced in effectiveness at high southern latitudes.

The IMO Polar Code (International Code for Ships Operating in Polar Waters), which entered into force for new vessels on 1 January 2017 and for existing vessels progressively thereafter, establishes the mandatory framework for ships operating south of 60°S. Under the Polar Code, vessels must hold a Polar Ship Certificate and operate with a Polar Water Operational Manual (PWOM). The Code requires that masters and chief mates hold Basic and Advanced Training for Ships Operating in Polar Waterscertificates (STCW A-V/4-1 and A-V/4-2), covering ice navigation, cold weather operations, emergency procedures specific to polar environments, and search and rescue in remote areas. Ships are classified into Polar Classes PC1 (highest) through PC7 (lowest) under the Polar Code; for Ross Sea operations, a minimum of Polar Class 6 (designed for summer/autumn operations in medium first-year ice) is effectively required, and icebreaker support (PC1–PC3 vessels) is necessary to transit McMurdo Sound during initial channel-breaking.

Sea ice is the dominant navigation hazard. The southern limit of sea ice in the Ross Sea varies significantly with season and year-to-year atmospheric variability. The operational approach season is generally December through February, when the sea ice retreats sufficiently for assisted navigation to McMurdo Sound. The earliest icebreaker operations to begin channel-cutting typically commence in November. By March, sea ice begins reforming rapidly and all vessels must clear the area. Pack ice consists of floes ranging from small fragments to multi-year pressure ridges, requiring constant radar watch, slow speeds, and, for unescorted vessels, regular assessment of ice concentration using satellite imagery (available from the USNIC, NSIDC, and the European Space Agency's Copernicus programme). GPS navigation is reliable at Ross Sea latitudes, but magnetic compass deviation is significant and highly variable at high southern latitudes — true and gyrocompass references are essential. Magnetic variation at McMurdo is approximately 140° East, making magnetic compass navigation effectively unreliable without careful correction.

Iceberg hazard is a year-round concern, even in summer. Tabular icebergs calved from the Ross Ice Shelf may measure tens to hundreds of kilometres in length and persist for years. They are detected by radar but may not appear on charts as their positions change continuously. USNIC issues regular iceberg position updates (particularly for large bergs greater than 10 nautical miles in length, which are tracked individually). Growlers — small pieces of ice barely visible above the surface — are an extreme hazard in open water near the ice edge and are not reliably detected by conventional marine radar. Continuous visual watch and reduced speed in ice-adjacent waters are mandatory.

Search and rescue (SAR) in the Ross Sea is a serious practical concern given the remoteness of the area. There is no dedicated SAR infrastructure — no Coastguard, no SAR vessels on standby, no helicopter rescue services beyond those that can be diverted from research stations. SAR coordination for the Ross Sea is the responsibility of the Rescue Coordination Centre New Zealand (RCCNZ) at Lower Hutt, Wellington, which coordinates with USAP resources at McMurdo, other Antarctic stations, and any vessels in the vicinity. EPIRB (Emergency Position Indicating Radio Beacon) activation via COSPAS-SARSAT is the primary distress alerting mechanism, but response times will be measured in days rather than hours. Vessels operating in the Ross Sea should conduct thorough emergency preparedness, including immersion suit drills, survival equipment checks, and life raft inspection to the highest standard.

8. Environmental Issues & Conservation

The establishment of the Ross Sea Marine Protected Area in October 2016 (entering into force in December 2017) represented a landmark achievement in international ocean conservation. Covering 1.55 million km² — an area larger than the combined land area of France and Germany — the Ross Sea MPA is the world's largest Marine Protected Area. It was agreed by consensus among all 25 member states of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), after more than five years of diplomatic effort by the United States and New Zealand. The MPA designates a General Protection Zone (no commercial fishing permitted) and a smaller Special Research Zone (limited scientific fishing under CCAMLR authorisation). The MPA is subject to review every 35 years — a provision that reflects the compromises necessary to achieve consensus, as some CCAMLR members (notably Russia and China) had previously blocked agreement on grounds of sovereign fishing rights.

Before the MPA's establishment, the Ross Sea was the target of a growing Antarctic toothfish longline fishery, with vessels from New Zealand, Russia, South Korea, and other nations fishing under CCAMLR quotas. Antarctic toothfish (Dissostichus mawsoni), marketed as “Chilean sea bass” or “Patagonian sea bass” in high-end restaurant markets, commands very high prices ($30–60 per kg wholesale). Given the species' slow growth rate and ecological centrality as the apex fish predator of the Ross Sea ecosystem, and its importance as prey for Weddell seals and Type C orcas, scientific concern about the impact of commercial fishing on the ecosystem was substantial. The MPA effectively ended commercial toothfish fishing in the majority of Ross Sea waters, though limited scientific catch is still authorised in the Special Research Zone.

Climate change is imposing increasingly visible changes on the Ross Sea environment. After a period of counter-intuitive sea ice expansion in the Ross Sea (driven by changing wind patterns linked to the Southern Annular Mode and ozone hole recovery), a dramatic and sustained decline in Ross Sea sea ice extent began around 2016 and has continued. The 2023 Antarctic sea ice season recorded the lowest sea ice extent since satellite observations began, with the Ross Sea sector showing particularly significant losses. Changes in sea ice timing and extent affect the Ross Sea Polynya's seasonal productivity, the breeding success of Emperor penguins (which depend on stable sea ice for their winter breeding colonies), and the dynamics of Antarctic Bottom Water formation. Reduced sea ice extent also increases surface ocean exposure to the atmosphere, potentially accelerating CO₂ uptake and altering the carbonate chemistry of Southern Ocean waters.

Mount Erebus volcanic degassing is a natural but significant source of atmospheric gases in the Ross Sea region. The volcano's persistent lava lake releases substantial quantities of sulphur dioxide (SO₂), hydrogen chloride (HCl), and fluorine compounds into the lower atmosphere. While this degassing is natural and has continued for at least 13,000 years, it contributes locally to atmospheric chemistry and represents a hazard for aircraft and helicopter operations near the summit. The Antarctic ozone hole — the seasonal depletion of stratospheric ozone over Antarctica caused by anthropogenic chlorofluorocarbon emissions — results in elevated UV-B radiation reaching the Ross Sea surface in spring (September–November). This elevated UV has been shown to inhibit phytoplankton photosynthesis in the surface waters and may affect the DNA of marine organisms. The Montreal Protocol and its amendments have progressively reduced ozone-depleting substance emissions globally, and the ozone hole is expected to recover to pre-1980 conditions by approximately 2065, though climate change interactions complicate the timeline.

Under the IMO Polar Code amendments and the Antarctic Treaty Environmental Protocol, vessels operating in the Ross Sea and Antarctic Treaty Area waters south of 60°S are prohibited from discharging oil, oily water, sewage, garbage, or food waste into the sea. The ban on heavy fuel oil (HFO) in Antarctic Treaty Area waters — phased in from 2024 — requires expedition vessels and resupply ships to use cleaner distillate fuels, significantly reducing the risk of catastrophic oil spills in the event of a grounding or sinking. Given the complete absence of any oil spill response capability in the Ross Sea, a major spill would be effectively uncontrollable, making prevention through fuel type restriction and strict navigation safety standards the only realistic approach.