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106-616: The harbour was formed by a drowned glacial valley which succumbed to sea level rise after glaciation . The Sackville River now empties into the upper end of the harbour in Bedford Basin . The harbour also includes the Northwest Arm and The Narrows, a constricted passage to Bedford Basin Halifax Harbour has been polluted as a result of two centuries of direct raw sewage discharge into its waters. Health concerns in

212-709: A collision between the French munitions ship Mont-Blanc and the Norwegian ship Imo destroyed part of Halifax and Dartmouth . The Royal Canadian Navy maintains a large base housing Maritime Forces Atlantic along the western side of The Narrows, as well as an ammunition depot on the northeastern shore of Bedford Basin, CFAD Bedford. There are strict security regulations relating to vessels navigating near Navy facilities and anchorages. There are two large suspension bridges crossing The Narrows: After Confederation in 1867, boosters of Halifax expected federal help to make

318-451: A consistent time period, assessments can attribute contributions to sea level rise and provide early indications of change in trajectory. This helps to inform adaptation plans. The different techniques used to measure changes in sea level do not measure exactly the same level. Tide gauges can only measure relative sea level. Satellites can also measure absolute sea level changes. To get precise measurements for sea level, researchers studying

424-445: A fishing vessel has the red light at top and the white light below. To remember this, some people use the mnemonic "white cap, red nose" to reflect the idea that pilots consumed a lot of alcohol while waiting for ships, thus the white captain's cap with a red nose below it. Pilot boats often also use bright colours, like flashy yellow, to make them clearly visible and distinctive in even the worst conditions. This last mainly applies to

530-415: A highly visible colour such as orange, red or yellow. In terms of design, monohull hullforms are most commonly used, though examples of catamarans , SWATHs and Wave Piercing Hulls also exist. Although some pilot boats are still constructed from steel, the need to travel quickly means lighter weight materials such as aluminium, fibreglass and composites are now commonly used. In some instances, such as

636-487: A larger role over such timescales. Ice loss from Antarctica is likely to dominate very long-term SLR, especially if the warming exceeds 2 °C (3.6 °F). Continued carbon dioxide emissions from fossil fuel sources could cause additional tens of metres of sea level rise, over the next millennia. Burning of all fossil fuels on Earth is sufficient to melt the entire Antarctic ice sheet, causing about 58 m (190 ft) of sea level rise. Year 2021 IPCC estimates for

742-701: A much longer period. Coverage of tide gauges started mainly in the Northern Hemisphere . Data for the Southern Hemisphere remained scarce up to the 1970s. The longest running sea-level measurements, NAP or Amsterdam Ordnance Datum were established in 1675, in Amsterdam . Record collection is also extensive in Australia . They include measurements by Thomas Lempriere , an amateur meteorologist, beginning in 1837. Lempriere established

848-508: A period of thousands of years. The size of the rise in sea level implies a large contribution from the Antarctic and Greenland ice sheets. Levels of atmospheric carbon dioxide of around 400 parts per million (similar to 2000s) had increased temperature by over 2–3 °C (3.6–5.4 °F) around three million years ago. This temperature increase eventually melted one third of Antarctica's ice sheet, causing sea levels to rise 20 meters above

954-576: A range of 28–61 cm (11–24 in). The "moderate" scenario, where CO 2 emissions take a decade or two to peak and its atmospheric concentration does not plateau until the 2070s is called RCP 4.5. Its likely range of sea level rise is 36–71 cm (14–28 in). The highest scenario in RCP8.5 pathway sea level would rise between 52 and 98 cm ( 20 + 1 ⁄ 2 and 38 + 1 ⁄ 2  in). AR6 had equivalents for both scenarios, but it estimated larger sea level rise under both. In AR6,

1060-481: A range with a lower and upper limit to reflect the unknowns. The scenarios in the 2013–2014 Fifth Assessment Report (AR5) were called Representative Concentration Pathways , or RCPs and the scenarios in the IPCC Sixth Assessment Report (AR6) are known as Shared Socioeconomic Pathways , or SSPs. A large difference between the two was the addition of SSP1-1.9 to AR6, which represents meeting

1166-665: A sea-level benchmark on a small cliff on the Isle of the Dead near the Port Arthur convict settlement in 1841. Together with satellite data for the period after 1992, this network established that global mean sea level rose 19.5 cm (7.7 in) between 1870 and 2004 at an average rate of about 1.44 mm/yr. (For the 20th century the average is 1.7 mm/yr.) By 2018, data collected by Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) had shown that

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1272-470: A sharp reduction in greenhouse gas emissions, this may increase to hundreds of millions in the latter decades of the century. Local factors like tidal range or land subsidence will greatly affect the severity of impacts. For instance, sea level rise in the United States is likely to be two to three times greater than the global average by the end of the century. Yet, of the 20 countries with

1378-593: A version of SSP5-8.5 where these processes take place, and in that case, sea level rise of up to 1.6 m ( 5 + 1 ⁄ 3  ft) by 2100 could not be ruled out. The greatest uncertainty with sea level rise projections is associated with the so-called marine ice sheet instability (MISI), and, even more so, Marine Ice Cliff Instability (MICI). These processes are mainly associated with West Antarctic Ice Sheet, but may also apply to some of Greenland's glaciers. The former suggests that when glaciers are mostly underwater on retrograde (backwards-sloping) bedrock,

1484-620: Is a type of boat used to transport maritime pilots between land and the inbound or outbound ships that they are piloting. Pilot boats were once sailing boats that had to be fast because the first pilot to reach the incoming ship got the business. Today, pilot boats are scheduled by telephoning the ship agents/representatives prior to arrival. Pilots and the work functions of the maritime pilot go back to Ancient Greece and Roman times, when incoming ships' captains employed locally experienced harbour captains, mainly local fishermen , to bring their vessels safely into port. Eventually, in light of

1590-402: Is by lowering the global temperature to 1 °C (1.8 °F) below the preindustrial level. This would be 2 °C (3.6 °F) below the temperature of 2020. Other researchers suggested that a climate engineering intervention to stabilize the ice sheet's glaciers may delay its loss by centuries and give more time to adapt. However this is an uncertain proposal, and would end up as one of

1696-518: Is connected to the mainland by road. Melville Island forms the eastern boundary of Melville Cove and is also the location of the Armdale Yacht Club . An adjacent residential community named itself after the cove. Although outside the defined harbour limits, Lawlor Island and Devils Island are also frequently included in descriptions of Halifax Harbour and the surrounding area. Halifax's official harbour limit for navigational purposes

1802-464: Is delineated by a line running from Herring Cove on the west side of the main channel, to the northern end of McNabs Island, then from McNabs Island across the Eastern Passage to the actual community of Eastern Passage on the east side of the island. The harbour is marked by an extensive network of buoys and lighthouses , starting with Sambro Island Lighthouse at the harbour approaches,

1908-454: Is due to the high level of inertia in the carbon cycle and the climate system, owing to factors such as the slow diffusion of heat into the deep ocean , leading to a longer climate response time. A 2018 paper estimated that sea level rise in 2300 would increase by a median of 20 cm (8 in) for every five years CO 2 emissions increase before peaking. It shows a 5% likelihood of a 1 m ( 3 + 1 ⁄ 2  ft) increase due to

2014-450: Is noted for many shipwrecks both in the inner and outer harbour. A few ships were sunk at the edge of the harbour approaches during World War II by German U-boats but the vast majority were claimed by harbour accidents. Mapping of the harbour revealed about 45 shipwrecks in the harbour. Near the mouth of the harbour, over 50 magnetic anomalies have been discovered, most of which also represent shipwrecks with many others buried underneath

2120-465: Is now unstoppable. However the temperature changes in future, the warming of 2000–2019 had already damaged the ice sheet enough for it to eventually lose ~3.3% of its volume. This is leading to 27 cm ( 10 + 1 ⁄ 2  in) of future sea level rise. At a certain level of global warming, the Greenland ice sheet will almost completely melt. Ice cores show this happened at least once over

2226-520: Is the East Antarctic Ice Sheet (EAIS). It is 2.2 km thick on average and holds enough ice to raise global sea levels by 53.3 m (174 ft 10 in) Its great thickness and high elevation make it more stable than the other ice sheets. As of the early 2020s, most studies show that it is still gaining mass. Some analyses have suggested it began to lose mass in the 2000s. However they over-extrapolated some observed losses on to

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2332-409: Is the fastest it had been over at least the past 3,000 years. While sea level rise is uniform around the globe, some land masses are moving up or down as a consequence of subsidence (land sinking or settling) or post-glacial rebound (land rising as melting ice reduces weight). Therefore, local relative sea level rise may be higher or lower than the global average. Changing ice masses also affect

2438-462: Is the largest and most influential scientific organization on climate change, and since 1990, it provides several plausible scenarios of 21st century sea level rise in each of its major reports. The differences between scenarios are mainly due to uncertainty about future greenhouse gas emissions. These depend on future economic developments, and also future political action which is hard to predict. Each scenario provides an estimate for sea level rise as

2544-633: Is to be believed, the first official Bristol Channel pilot was barge master George James Ray, appointed by the Corporation of Bristol in May 1497 to pilot John Cabot 's Matthew from Bristol harbour to the open sea beyond the Bristol channel . In 1837 Pilot George Ray guided Brunel 's SS Great Western , and in 1844 William Ray piloted the larger SS Great Britain on her maiden voyage. In 1840, there were only eight New York pilot boats. They were

2650-784: The Phantom, No. 1; Washington, No. 2; New York, No. 3; Jacob Bell, No. 4; Blossom, No. 5; T. H. Smith, No. 6; John E. Davidson, No. 7; and the Virginia, No. 8. In 1860 there were twenty-one New York pilot boats and four under the New Jersey dispensation. In the spring of 1896, the New York and New Jersey pilots discarded pilot-boats and moved them to the Erie Basin in Brooklyn. They were for sale because of

2756-529: The Amundsen Sea Embayment played a disproportionate role. The median estimated increase in sea level rise from Antarctica by 2100 is ~11 cm (5 in). There is no difference between scenarios, because the increased warming would intensify the water cycle and increase snowfall accumulation over the EAIS at about the same rate as it would increase ice loss from WAIS. However, most of

2862-502: The Earth 's temperature by many decades, and sea level rise will therefore continue to accelerate between now and 2050 in response to warming that has already happened. What happens after that depends on human greenhouse gas emissions . If there are very deep cuts in emissions, sea level rise would slow between 2050 and 2100. It could then reach by 2100 slightly over 30 cm (1 ft) from now and approximately 60 cm (2 ft) from

2968-685: The Hooghly River between Calcutta and the sea. The Zodiac and Adventuress are both listed with the National Register of Historic Places and are now cruising in Washington state after restorations. Modern pilot boats can be from 7 metres to over 25 metres (23–82 ft) in length, built to withstand heavy seas and bumping against 100,000 ton tanker and cruise ships. They are high-powered and hence both very quick and durable purpose-built boats. They are normally painted

3074-599: The Pacific Decadal Oscillation (PDO) and the El Niño–Southern Oscillation (ENSO) change from one state to the other. The PDO is a basin-wide climate pattern consisting of two phases, each commonly lasting 10 to 30 years. The ENSO has a shorter period of 2 to 7 years. The global network of tide gauges is the other important source of sea-level observations. Compared to the satellite record, this record has major spatial gaps but covers

3180-605: The SROCC assessed several studies attempting to estimate 2300 sea level rise caused by ice loss in Antarctica alone, arriving at projected estimates of 0.07–0.37 metres (0.23–1.21 ft) for the low emission RCP2.6 scenario, and 0.60–2.89 metres (2.0–9.5 ft) in the high emission RCP8.5 scenario. This wide range of estimates is mainly due to the uncertainties regarding marine ice sheet and marine ice cliff instabilities. The world's largest potential source of sea level rise

3286-637: The bedrock underlying the WAIS lies well below sea level, and it has to be buttressed by the Thwaites and Pine Island glaciers. If these glaciers were to collapse, the entire ice sheet would as well. Their disappearance would take at least several centuries, but is considered almost inevitable, as their bedrock topography deepens inland and becomes more vulnerable to meltwater, in what is known as marine ice sheet instability. The contribution of these glaciers to global sea levels has already accelerated since

Halifax Harbour - Misplaced Pages Continue

3392-430: The ice shelves propping them up are gone. The collapse then exposes the ice masses following them to the same instability, potentially resulting in a self-sustaining cycle of cliff collapse and rapid ice sheet retreat. This theory had been highly influential - in a 2020 survey of 106 experts, the 2016 paper which suggested 1 m ( 3 + 1 ⁄ 2  ft) or more of sea level rise by 2100 from Antarctica alone,

3498-505: The 1990s caused the shut-down of all harbour beaches. The Harbour Solutions project, initiated in the year 2000, was a CA$ 400 million project which attempted to remediate the area, with limited success. The Mi'kmaq First Nation, long the occupants of this territory, called the harbour Kjipuktuk in their language. It was transliterated in English as "Chebucto". It runs in a northwest–southeast direction. Based on average vessel speeds,

3604-973: The 19th century. With high emissions it would instead accelerate further, and could rise by 1.0 m ( 3 + 1 ⁄ 3  ft) or even 1.6 m ( 5 + 1 ⁄ 3  ft) by 2100. In the long run, sea level rise would amount to 2–3 m (7–10 ft) over the next 2000 years if warming stays to its current 1.5 °C (2.7 °F) over the pre-industrial past. It would be 19–22 metres (62–72 ft) if warming peaks at 5 °C (9.0 °F). Rising seas affect every coastal and island population on Earth. This can be through flooding, higher storm surges , king tides , and tsunamis . There are many knock-on effects. They lead to loss of coastal ecosystems like mangroves . Crop yields may reduce because of increasing salt levels in irrigation water. Damage to ports disrupts sea trade. The sea level rise projected by 2050 will expose places currently inhabited by tens of millions of people to annual flooding. Without

3710-584: The Antarctic continent stores around 60% of the world's fresh water. Excluding groundwater this is 90%. Antarctica is experiencing ice loss from coastal glaciers in the West Antarctica and some glaciers of East Antarctica . However it is gaining mass from the increased snow build-up inland, particularly in the East. This leads to contradicting trends. There are different satellite methods for measuring ice mass and change. Combining them helps to reconcile

3816-527: The Berkeley Class vessels produced in Australia, a combination of materials is used. Pilots identified pilot boats with a large number on the mainsail and by flying a large pilot flag, bisected vertically into two colours, usually white and blue, which added to the boat's visibility. In distress, they would fire rockets and blue-lights at night. A brass signal gun was carried to be used when there

3922-503: The Earth was 2 °C (3.6 °F) warmer than pre-industrial temperatures was 120,000 years ago. This was when warming due to Milankovitch cycles (changes in the amount of sunlight due to slow changes in the Earth's orbit) caused the Eemian interglacial . Sea levels during that warmer interglacial were at least 5 m (16 ft) higher than now. The Eemian warming was sustained over

4028-445: The Eastern Passage, which runs on the east side of McNabs Island; however, continuous silting makes charted depths unreliable. Large vessels have compulsory pilotage, with harbour pilots boarding at the pilot station off Chebucto Head. Vessels wishing to transit The Narrows between the outer harbour and Bedford Basin must travel one at a time; this rule was established after the disastrous Halifax Explosion of December 6, 1917 when

4134-438: The Greenland ice sheet between 1992 and 2018 amounted to 3,902 gigatons (Gt) of ice. This is equivalent to a SLR contribution of 10.8 mm. The contribution for the 2012–2016 period was equivalent to 37% of sea level rise from land ice sources (excluding thermal expansion). This observed rate of ice sheet melting is at the higher end of predictions from past IPCC assessment reports. In 2021, AR6 estimated that by 2100,

4240-598: The Halifax Intermodal Terminal (HIT) adjacent to the Richmond Terminals. In addition to HPA facilities, the following users have port facilities: Halifax Harbour has long been polluted as a result of two centuries of direct raw sewage discharge into its waters. The harbour's deep water, tidal dispersal of surface wastes and a relatively small population of the city of Halifax resulted in the harbour's presenting few health concerns until

4346-612: The ICR's own attempts to promote traffic to Halifax, most Canadian exporters sent their wares by train though Boston or Portland. Harbour promoters fought an uphill battle to finance the large-scale port facilities Halifax lacked, succeeding just before the First World War with the start of construction of the large docking facilities at Ocean Terminals in Halifax's South End . The war at last boosted Halifax's harbour into prominence on

Halifax Harbour - Misplaced Pages Continue

4452-604: The Last Interglacial SLR is unlikely to have been higher than 2.7 m (9 ft), as higher values in other research, such as 5.7 m ( 18 + 1 ⁄ 2  ft), appear inconsistent with the new paleoclimate data from The Bahamas and the known history of the Greenland Ice Sheet. Even if the temperature stabilizes, significant sea-level rise (SLR) will continue for centuries, consistent with paleo records of sea level rise. This

4558-620: The North Atlantic. The Halifax Port Authority is a federally appointed agency which administers and operates various port properties on the harbour. Previously run by the National Harbours Board, the HPA is now a locally run organization. HPA facilities include: All HPA facilities are serviced by CN. It provides on-dock daily train service to Montreal , Toronto , Detroit and Chicago . The railway also operates

4664-605: The SSP1-1.9 scenario would result in sea level rise in the 17–83% range of 37–86 cm ( 14 + 1 ⁄ 2 –34 in). In the SSP1-2.6 pathway the range would be 46–99 cm (18–39 in), for SSP2-4.5 a 66–133 cm (26– 52 + 1 ⁄ 2  in) range by 2100 and for SSP5-8.5 a rise of 98–188 cm ( 38 + 1 ⁄ 2 –74 in). It stated that the "low-confidence, high impact" projected 0.63–1.60 m (2–5 ft) mean sea level rise by 2100, and that by 2150,

4770-522: The SSP1-2.6 pathway results in a range of 32–62 cm ( 12 + 1 ⁄ 2 – 24 + 1 ⁄ 2  in) by 2100. The "moderate" SSP2-4.5 results in a 44–76 cm ( 17 + 1 ⁄ 2 –30 in) range by 2100 and SSP5-8.5 led to 65–101 cm ( 25 + 1 ⁄ 2 –40 in). This general increase of projections in AR6 came after the improvements in ice-sheet modeling and the incorporation of structured expert judgements. These decisions came as

4876-561: The WAIS to contribute up to 41 cm (16 in) by 2100 under the low-emission scenario and up to 57 cm (22 in) under the highest-emission one. Ice cliff instability would cause a contribution of 1 m ( 3 + 1 ⁄ 2  ft) or more if it were applicable. The melting of all the ice in West Antarctica would increase the total sea level rise to 4.3 m (14 ft 1 in). However, mountain ice caps not in contact with water are less vulnerable than

4982-444: The amount of sea level rise over the next 2,000 years project that: Sea levels would continue to rise for several thousand years after the ceasing of emissions, due to the slow nature of climate response to heat. The same estimates on a timescale of 10,000 years project that: Variations in the amount of water in the oceans, changes in its volume, or varying land elevation compared to the sea surface can drive sea level changes. Over

5088-574: The average sea level rose by 15–25 cm (6–10 in), with an increase of 2.3 mm (0.091 in) per year since the 1970s. This was faster than the sea level had ever risen over at least the past 3,000 years. The rate accelerated to 4.62 mm (0.182 in)/yr for the decade 2013–2022. Climate change due to human activities is the main cause. Between 1993 and 2018, melting ice sheets and glaciers accounted for 44% of sea level rise , with another 42% resulting from thermal expansion of water . Sea level rise lags behind changes in

5194-422: The average world ocean temperature by 0.01 °C (0.018 °F) would increase atmospheric temperature by approximately 10 °C (18 °F). So a small change in the mean temperature of the ocean represents a very large change in the total heat content of the climate system. Winds and currents move heat into deeper parts of the ocean. Some of it reaches depths of more than 2,000 m (6,600 ft). When

5300-459: The best Paris climate agreement goal of 1.5 °C (2.7 °F). In that case, the likely range of sea level rise by 2100 is 28–55 cm (11– 21 + 1 ⁄ 2  in). The lowest scenario in AR5, RCP2.6, would see greenhouse gas emissions low enough to meet the goal of limiting warming by 2100 to 2 °C (3.6 °F). It shows sea level rise in 2100 of about 44 cm (17 in) with

5406-485: The best-case scenario, ice sheet under SSP1-2.6 gains enough mass by 2100 through surface mass balance feedbacks to reduce the sea levels by 2 cm (1 in). In the worst case, it adds 15 cm (6 in). For SSP5-8.5, the best-case scenario is adding 5 cm (2 in) to sea levels, and the worst-case is adding 23 cm (9 in). Greenland's peripheral glaciers and ice caps crossed an irreversible tipping point around 1997. Sea level rise from their loss

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5512-671: The change from wood and sail to steel and steam pilot boats. In Great Britain, pilot boats were rigged as schooners in Fleetwood , Swansea and Liverpool . In Liverpool, the Pioneer, No. 6 was built in 1852 and was 53-tons. The clipper George Holt, No. 10 was built in 1892. The Bengal Pilot Service was established by the British East India Company to control piloting . The pilot boats were responsible for guiding East Indiaman , and other vessels, up and down

5618-535: The city's natural harbour Canada's official winter port and a gateway for trade with Europe. Halifax's advantages included its location just off the Great Circle route made it the closest to Europe of any mainland North American port. But the new Intercolonial Railway (ICR) took an indirect, southerly route for military and political reasons, and the national government made little effort to promote Halifax as Canada's winter port. Ignoring appeals to nationalism and

5724-459: The contribution from these is thought to be small. Glacier retreat and ocean expansion have dominated sea level rise since the start of the 20th century. Some of the losses from glaciers are offset when precipitation falls as snow, accumulates and over time forms glacial ice. If precipitation, surface processes and ice loss at the edge balance each other, sea level remains the same. Because of this precipitation began as water vapor evaporated from

5830-517: The differences. However, there can still be variations between the studies. In 2018, a systematic review estimated average annual ice loss of 43 billion tons (Gt) across the entire continent between 1992 and 2002. This tripled to an annual average of 220 Gt from 2012 to 2017. However, a 2021 analysis of data from four different research satellite systems ( Envisat , European Remote-Sensing Satellite , GRACE and GRACE-FO and ICESat ) indicated annual mass loss of only about 12 Gt from 2012 to 2016. This

5936-456: The distribution of sea water around the globe through gravity. Several approaches are used for sea level rise (SLR) projections. One is process-based modeling, where ice melting is computed through an ice-sheet model and rising sea temperature and expansion through a general circulation model , and then these contributions are added up. The so-called semi-empirical approach instead applies statistical techniques and basic physical modeling to

6042-428: The empirical 2.5 °C (4.5 °F) upper limit from ice cores. If temperatures reach or exceed that level, reducing the global temperature to 1.5 °C (2.7 °F) above pre-industrial levels or lower would prevent the loss of the entire ice sheet. One way to do this in theory would be large-scale carbon dioxide removal , but there would still be cause of greater ice losses and sea level rise from Greenland than if

6148-403: The extremely low probability of large climate change-induced increases in precipitation greatly elevating ice sheet surface mass balance .) In 2020, 106 experts who contributed to 6 or more papers on sea level estimated median 118 cm ( 46 + 1 ⁄ 2  in) SLR in the year 2300 for the low-warming RCP2.6 scenario and the median of 329 cm ( 129 + 1 ⁄ 2  in) for

6254-559: The global mean sea level was rising by 3.2 mm ( 1 ⁄ 8  in) per year. This was double the average 20th century rate. The 2023 World Meteorological Organization report found further acceleration to 4.62 mm/yr over the 2013–2022 period. These observations help to check and verify predictions from climate change simulations. Regional differences are also visible in the tide gauge data. Some are caused by local sea level differences. Others are due to vertical land movements. In Europe , only some land areas are rising while

6360-1034: The greatest exposure to sea level rise, twelve are in Asia , including Indonesia , Bangladesh and the Philippines. The resilience and adaptive capacity of ecosystems and countries also varies, which will result in more or less pronounced impacts. The greatest impact on human populations in the near term will occur in the low-lying Caribbean and Pacific islands . Sea level rise will make many of them uninhabitable later this century. Societies can adapt to sea level rise in multiple ways. Managed retreat , accommodating coastal change , or protecting against sea level rise through hard-construction practices like seawalls are hard approaches. There are also soft approaches such as dune rehabilitation and beach nourishment . Sometimes these adaptation strategies go hand in hand. At other times choices must be made among different strategies. Poorer nations may also struggle to implement

6466-574: The harbour is strategically located approximately one hour's sailing time north of the Great Circle Route between the Eastern Seaboard and Europe . As such, it is the first inbound and last outbound port of call in eastern North America with transcontinental rail connections. The harbour is largely formed by a drowned glacial valley which succumbed to sea level rise since glaciation . The Sackville River now empties into

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6572-490: The harbour limits is Georges Island , a glacial drumlin similar to its dryland counterpart at Citadel Hill . Several small islands are located in the Bedford Basin near Bedford and Burnside . In the Northwest Arm is a small peninsula known as Deadman's Island , named for being the burial location of War of 1812 prisoners of war. Just 200 m west of Deadman's Island is the equally small Melville Island , which

6678-536: The high-warming RCP8.5. The former scenario had the 5%–95% confidence range of 24–311 cm ( 9 + 1 ⁄ 2 – 122 + 1 ⁄ 2  in), and the latter of 88–783 cm ( 34 + 1 ⁄ 2 – 308 + 1 ⁄ 2  in). After 500 years, sea level rise from thermal expansion alone may have reached only half of its eventual level - likely within ranges of 0.5–2 m ( 1 + 1 ⁄ 2 – 6 + 1 ⁄ 2  ft). Additionally, tipping points of Greenland and Antarctica ice sheets are likely to play

6784-417: The hypothesis after 2016 often suggested that the ice shelves in the real world may collapse too slowly to make this scenario relevant, or that ice mélange - debris produced as the glacier breaks down - would quickly build up in front of the glacier and significantly slow or even outright stop the instability soon after it began. Due to these uncertainties, some scientists - including the originators of

6890-543: The hypothesis, Robert DeConto and David Pollard - have suggested that the best way to resolve the question would be to precisely determine sea level rise during the Last Interglacial . MICI can be effectively ruled out if SLR at the time was lower than 4 m (13 ft), while it is very likely if the SLR was greater than 6 m ( 19 + 1 ⁄ 2  ft). As of 2023, the most recent analysis indicates that

6996-415: The ice and oceans factor in ongoing deformations of the solid Earth . They look in particular at landmasses still rising from past ice masses retreating , and the Earth's gravity and rotation . Since the launch of TOPEX/Poseidon in 1992, an overlapping series of altimetric satellites has been continuously recording the sea level and its changes. These satellites can measure the hills and valleys in

7102-408: The ice on Earth would result in about 70 m (229 ft 8 in) of sea level rise, although this would require at least 10,000 years and up to 10 °C (18 °F) of global warming. The oceans store more than 90% of the extra heat added to the climate system by Earth's energy imbalance and act as a buffer against its effects. This means that the same amount of heat that would increase

7208-463: The incoming vessels. But fishing boats were heavy working boats, and filled with fishing equipment, and so a new type of boat was required. Early boats were developed from single masted cutters and twin masted yawls , and latterly into the specialist pilot cutter . These were effectively light-weight and over-powered single-masted boats with large, steeply angled keels, making them deep draft under power and shallow draft in lighter sail. If legend

7314-735: The largest potential source of sea level rise. However the West Antarctic ice sheet (WAIS) is substantially more vulnerable. Temperatures on West Antarctica have increased significantly, unlike East Antarctica and the Antarctic Peninsula . The trend is between 0.08 °C (0.14 °F) and 0.96 °C (1.73 °F) per decade between 1976 and 2012. Satellite observations recorded a substantial increase in WAIS melting from 1992 to 2017. This resulted in 7.6 ± 3.9 mm ( 19 ⁄ 64  ±  5 ⁄ 32  in) of Antarctica sea level rise. Outflow glaciers in

7420-414: The last million years, during which the temperatures have at most been 2.5 °C (4.5 °F) warmer than the preindustrial average. 2012 modelling suggested that the tipping point of the ice sheet was between 0.8 °C (1.4 °F) and 3.2 °C (5.8 °F). 2023 modelling has narrowed the tipping threshold to a 1.7 °C (3.1 °F)-2.3 °C (4.1 °F) range, which is consistent with

7526-427: The late 20th century when sewage build-up caused the shut-down of all harbour beaches. The Harbour Solutions project, initiated in the year 2000, was the culmination of three decades of discussion and planning regarding how the urban area would solve the expensive problem of sewage treatment and disposal. The CA$ 400 million project was expected to be completed in late 2008 when the final of three new treatment plants

7632-426: The majority of the ice sheet, which is located below the sea level. Its collapse would cause ~3.3 m (10 ft 10 in) of sea level rise. This disappearance would take an estimated 2000 years. The absolute minimum for the loss of West Antarctica ice is 500 years, and the potential maximum is 13,000 years. Once ice loss from the West Antarctica is triggered, the only way to restore it to near-present values

7738-507: The melting of Greenland ice sheet would most likely add around 6 cm ( 2 + 1 ⁄ 2  in) to sea levels under the low-emission scenario, and 13 cm (5 in) under the high-emission scenario. The first scenario, SSP1-2.6 , largely fulfils the Paris Agreement goals, while the other, SSP5-8.5, has the emissions accelerate throughout the century. The uncertainty about ice sheet dynamics can affect both pathways. In

7844-568: The most expensive projects ever attempted. Most ice on Greenland is in the Greenland ice sheet which is 3 km (10,000 ft) at its thickest. The rest of Greenland ice forms isolated glaciers and ice caps. The average annual ice loss in Greenland more than doubled in the early 21st century compared to the 20th century. Its contribution to sea level rise correspondingly increased from 0.07 mm per year between 1992 and 1997 to 0.68 mm per year between 2012 and 2017. Total ice loss from

7950-490: The muddy sediments. All historic shipwrecks in Halifax Harbour are protected by Nova Scotia's Special Places Act which makes it illegal to remove artifacts without a permit. Noteworthy wrecks are listed chronologically (with sinking dates): 44°37′N 63°33′W  /  44.617°N 63.550°W  / 44.617; -63.550  ( Halifax Harbour ) Sea level rise Between 1901 and 2018,

8056-432: The need to regulate the act of pilotage and ensure pilots had adequate insurance, the harbours themselves licensed pilots for each harbour. Although licensed by the harbour to operate within their jurisdiction, pilots were generally self-employed, meaning that they had to have quick transport to get them from the port to the incoming ships. As pilots were often still dual-employed, they used their own fishing boats to reach

8162-628: The observed ice-sheet erosion in Greenland and Antarctica had matched the upper-end range of the AR5 projections by 2020, and the finding that AR5 projections were likely too slow next to an extrapolation of observed sea level rise trends, while the subsequent reports had improved in this regard. Further, AR5 was criticized by multiple researchers for excluding detailed estimates the impact of "low-confidence" processes like marine ice sheet and marine ice cliff instability, which can substantially accelerate ice loss to potentially add "tens of centimeters" to sea level rise within this century. AR6 includes

8268-506: The observed sea level rise and its reconstructions from the historical geological data (known as paleoclimate modeling). It was developed because process-based model projections in the past IPCC reports (such as the Fourth Assessment Report from 2007) were found to underestimate the already observed sea level rise. By 2013, improvements in modeling had addressed this issue, and model and semi-empirical projections for

8374-473: The ocean gains heat, the water expands and sea level rises. Warmer water and water under great pressure (due to depth) expand more than cooler water and water under less pressure. Consequently, cold Arctic Ocean water will expand less than warm tropical water. Different climate models present slightly different patterns of ocean heating. So their projections do not agree fully on how much ocean heating contributes to sea level rise. The large volume of ice on

8480-543: The ocean surface, effects of climate change on the water cycle can even increase ice build-up. However, this effect is not enough to fully offset ice losses, and sea level rise continues to accelerate. The contributions of the two large ice sheets, in Greenland and Antarctica , are likely to increase in the 21st century. They store most of the land ice (~99.5%) and have a sea-level equivalent (SLE) of 7.4 m (24 ft 3 in) for Greenland and 58.3 m (191 ft 3 in) for Antarctica. Thus, melting of all

8586-475: The oldest operating lighthouse in North America . Deep draught vessels must use the main channel into the harbour, which runs on the west side of McNabs Island. The west entrance point marking the beginning of the inner approach using this channel is located near Chebucto Head, approximately 12 kilometres (7 mi) south of the limit. Shallow draught vessels (less than 2.5 metres, 8.2 ft) may use

8692-401: The other hand, the whole EAIS would not definitely collapse until global warming reaches 7.5 °C (13.5 °F), with a range between 5 °C (9.0 °F) and 10 °C (18 °F). It would take at least 10,000 years to disappear. Some scientists have estimated that warming would have to reach at least 6 °C (11 °F) to melt two thirds of its volume. East Antarctica contains

8798-454: The others are sinking. Since 1970, most tidal stations have measured higher seas. However sea levels along the northern Baltic Sea have dropped due to post-glacial rebound . An understanding of past sea level is an important guide to where current changes in sea level will end up. In the recent geological past, thermal expansion from increased temperatures and changes in land ice are the dominant reasons of sea level rise. The last time that

8904-651: The poorly observed areas. A more complete observational record shows continued mass gain. In spite of the net mass gain, some East Antarctica glaciers have lost ice in recent decades due to ocean warming and declining structural support from the local sea ice , such as Denman Glacier , and Totten Glacier . Totten Glacier is particularly important because it stabilizes the Aurora Subglacial Basin . Subglacial basins like Aurora and Wilkes Basin are major ice reservoirs together holding as much ice as all of West Antarctica. They are more vulnerable than

9010-556: The preindustrial levels. Since the Last Glacial Maximum , about 20,000 years ago, sea level has risen by more than 125 metres (410 ft). Rates vary from less than 1 mm/year during the pre-industrial era to 40+ mm/year when major ice sheets over Canada and Eurasia melted. Meltwater pulses are periods of fast sea level rise caused by the rapid disintegration of these ice sheets. The rate of sea level rise started to slow down about 8,200 years before today. Sea level

9116-507: The projected range for total sea level rise was 9.5–16.2 metres (31–53 ft) by the year 2300. Projections for subsequent years are more difficult. In 2019, when 22 experts on ice sheets were asked to estimate 2200 and 2300 SLR under the 5   °C warming scenario, there were 90% confidence intervals of −10 cm (4 in) to 740 cm ( 24 + 1 ⁄ 2  ft) and − 9 cm ( 3 + 1 ⁄ 2  in) to 970 cm (32 ft), respectively. (Negative values represent

9222-563: The rest of East Antarctica. Their collective tipping point probably lies at around 3 °C (5.4 °F) of global warming. It may be as high as 6 °C (11 °F) or as low as 2 °C (3.6 °F). Once this tipping point is crossed, the collapse of these subglacial basins could take place over as little as 500 or as much as 10,000 years. The median timeline is 2000 years. Depending on how many subglacial basins are vulnerable, this causes sea level rise of between 1.4 m (4 ft 7 in) and 6.4 m (21 ft 0 in). On

9328-458: The same approaches to adapt to sea level rise as richer states. Between 1901 and 2018, the global mean sea level rose by about 20 cm (7.9 in). More precise data gathered from satellite radar measurements found an increase of 7.5 cm (3.0 in) from 1993 to 2017 (average of 2.9 mm (0.11 in)/yr). This accelerated to 4.62 mm (0.182 in)/yr for 2013–2022. Paleoclimate data shows that this rate of sea level rise

9434-426: The same. The same estimate found that if the temperature stabilized below 2 °C (3.6 °F), 2300 sea level rise would still exceed 1.5 m (5 ft). Early net zero and slowly falling temperatures could limit it to 70–120 cm ( 27 + 1 ⁄ 2 –47 in). By 2021, the IPCC Sixth Assessment Report was able to provide estimates for sea level rise in 2150. Keeping warming to 1.5   °C under

9540-404: The sea caused by currents and detect trends in their height. To measure the distance to the sea surface, the satellites send a microwave pulse towards Earth and record the time it takes to return after reflecting off the ocean's surface. Microwave radiometers correct the additional delay caused by water vapor in the atmosphere . Combining these data with the location of the spacecraft determines

9646-476: The sea-surface height to within a few centimetres. These satellite measurements have estimated rates of sea level rise for 1993–2017 at 3.0 ± 0.4 millimetres ( 1 ⁄ 8  ±  1 ⁄ 64  in) per year. Satellites are useful for measuring regional variations in sea level. An example is the substantial rise between 1993 and 2012 in the western tropical Pacific. This sharp rise has been linked to increasing trade winds . These occur when

9752-420: The so-called pilot tenders: the vessels that go to the ships to bring the pilot on board of arriving ships or pick them up from departing ships. Depending on the local situation the tenders might be launched directly from a nearby harbour or they are coming from the central (large) pilot station : a pilot boat located at a pre-defined location at sea near a pilotage area. In earlier days nearly all pilots came from

9858-673: The specific regions. A structured expert judgement may be used in combination with modeling to determine which outcomes are more or less likely, which is known as "shifted SEJ". Semi-empirical techniques can be combined with the so-called "intermediate-complexity" models. After 2016, some ice sheet modeling exhibited the so-called ice cliff instability in Antarctica, which results in substantially faster disintegration and retreat than otherwise simulated. The differences are limited with low warming, but at higher warming levels, ice cliff instability predicts far greater sea level rise than any other approach. The Intergovernmental Panel on Climate Change

9964-434: The threshold was not breached in the first place. If the tipping point instead is durably but mildly crossed, the ice sheet would take between 10,000 and 15,000 years to disintegrate entirel, with a most likely estimate of 10,000 years. If climate change continues along its worst trajectory and temperatures continue to rise quickly over multiple centuries, it would only take 1,000 years. Pilot boat A pilot boat

10070-453: The total sea level rise in his scenario would be in the range of 0.98–4.82 m (3–16 ft) by 2150. AR6 also provided lower-confidence estimates for year 2300 sea level rise under SSP1-2.6 and SSP5-8.5 with various impact assumptions. In the best case scenario, under SSP1-2.6 with no ice sheet acceleration after 2100, the estimate was only 0.8–2.0 metres (2.6–6.6 ft). In the worst estimated scenario, SSP-8.5 with ice cliff instability,

10176-497: The upper end of the harbour in Bedford Basin ; however, its original river bed has been charted by the Canadian Hydrographic Service throughout the length of the harbour and beyond. The harbour includes the following geographic areas: The harbour is home to several small islands. The harbour limit is formed by the northern end of its largest island - McNabs Island . The largest island entirely within

10282-445: The water melts more and more of their height as their retreat continues, thus accelerating their breakdown on its own. This is widely accepted, but is difficult to model. The latter posits that coastal ice cliffs which exceed ~ 90 m ( 295 + 1 ⁄ 2  ft) in above-ground height and are ~ 800 m ( 2,624 + 1 ⁄ 2  ft) in basal (underground) height are likely to rapidly collapse under their own weight once

10388-464: The water. Lifeguards are now providing supervision during regular hours through to Labour Day weekend. However repeated breakdowns in the new system have resulted in swimming bans being regularly re-imposed and periodic resumption of raw sewage discharge. From early 2009 on swimming was no longer allowed in the harbour because the plant flooded and stopped working. On the weekend of July 4, 2010 some beaches (like Black Rock Beach) reopened. Halifax Harbour

10494-556: The year 2000. The Thwaites Glacier now accounts for 4% of global sea level rise. It could start to lose even more ice if the Thwaites Ice Shelf fails and would no longer stabilize it, which could potentially occur in mid-2020s. A combination of ice sheet instability with other important but hard-to-model processes like hydrofracturing (meltwater collects atop the ice sheet, pools into fractures and forces them open) or smaller-scale changes in ocean circulation could cause

10600-594: The year 2100 are now very similar. Yet, semi-empirical estimates are reliant on the quality of available observations and struggle to represent non-linearities, while processes without enough available information about them cannot be modeled. Thus, another approach is to combine the opinions of a large number of scientists in what is known as a structured expert judgement (SEJ). Variations of these primary approaches exist. For instance, large climate models are always in demand, so less complex models are often used in their place for simpler tasks like projecting flood risk in

10706-450: Was almost constant for the last 2,500 years. The recent trend of rising sea level started at the end of the 19th or beginning of the 20th century. The three main reasons why global warming causes sea levels to rise are the expansion of oceans due to heating , water inflow from melting ice sheets and water inflow from glaciers. Other factors affecting sea level rise include changes in snow mass, and flow from terrestrial water storage, though

10812-407: Was considered even more important than the 2014 IPCC Fifth Assessment Report . Even more rapid sea level rise was proposed in a 2016 study led by Jim Hansen , which hypothesized multi-meter sea level rise in 50–100 years as a plausible outcome of high emissions, but it remains a minority view amongst the scientific community. Marine ice cliff instability had also been very controversial, since it

10918-509: Was due to greater ice gain in East Antarctica than estimated earlier. In the future, it is known that West Antarctica at least will continue to lose mass, and the likely future losses of sea ice and ice shelves , which block warmer currents from direct contact with the ice sheet, can accelerate declines even in East Antarctica. Altogether, Antarctica is the source of the largest uncertainty for future sea level projections. In 2019,

11024-421: Was fog and sometimes on fair days. Pilot boats are specially marked to indicate their function. During the day they fly the "H" flag and normally the word PILOT (or PILOTS ) is written in clearly visible, large, letters on the sides. At night they have special navigation lights: in addition to the "normal" navigation lights, a pilot boat has a white round light at top and below that a red round light, while

11130-666: Was opened. Testing of harbour waters in July 2008, with two of the three sewage treatment plants on-line, indicated that they are safe for swimming. Municipal public beaches at Black Rock Beach in Point Pleasant Park and at the Dingle Beach in Sir Sandford Fleming Park were officially re-opened on Saturday, August 2, 2008 (Natal Day weekend) after a 30-year closure due to sewage contamination in

11236-472: Was proposed as a modelling exercise, and the observational evidence from both the past and the present is very limited and ambiguous. So far, only one episode of seabed gouging by ice from the Younger Dryas period appears truly consistent with this theory, but it had lasted for an estimated 900 years, so it is unclear if it supports rapid sea level rise in the present. Modelling which investigated

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