Analysis of challenges facing the Scotian Shelf

The Scotian Shelf is related to geographic places like the Grand Banks, the Gulf of Maine, and the St. Lawrence Gulf. It is bounded to the east, west, and south by the Laurentian, the Northeast Channels, and a continental slope. A persistent coastally trapped current known as the Nova Scotia Current and a southwestward along slope current located at the shelf break defines the mean circulation on the Scotian Shelf. The latter comes from Labrador Current's offshore branch. The irregular topography of the Scotian Shelf, which is composed of banks and basins, affects the mesoscale structure of the flow, which there is a correlation with cyclonic and anticyclonic circulation characteristics, respectively. Previous studies show that the main physical processes that influence circulation on the Scotian Shelf are baroclinic and barotropic. The geostrophic waves approximated from concurrent density transects agreed with the winter circulation measured along the Halifax Line (HL) (Dever et al., 2016). The time-varying local surface wind tension on the Scotian Shelf significantly affects the circulation's temporal variability. Water columns shallow than 100 m have a more excellent reply in both the inertial and synoptic frequency bands, with a more significant response (Dever et al.,2016). Production of travelling shelf currency by remote winds and huge-scale meteorological forcing relates to temporal variability in the subsurface pressure places and bottom temperature at low frequencies. The Labrador Current's intensity and hydrographic signature were affected. The Scottian Self faces various threats from human activity like pollution, climate change, and overfishing, which endanger different marine life. 

Human activities; pollution, and overfishing 

Illegal leaks and discharges, like the introduction of oil from shipping traffic, underwater waste, chemical pollutants from sea vessels and hydrocarbon offshore extraction operations, and introducing of invasive organisms and diseases by ballast water, all have a substantial impact on the Scottian Shelf, according to the research of Human Activities. Shipwrecks, post-war chemical and unexploded ordinance disposal sites, and shipwrecks are among the areas that need new risk assessments ( Aquarone & Adams n.d) . Some large-scale environmental disasters have occurred, including the disappearance of the Arrow oil tanker and the sinking of other sea vessels. Finally, pollution caused by human activity is a significant problem because it results in the extinction of aquatic organisms, disrupting ecological equilibrium. 

There are also the broader environmental costs of overfishing the fisheries resource. The International GLOBEC Cod investigated how different cod communities react to climate change in North Atlantic, like the Scotian Shelf. The Eastern Scotian Shelf Integrated Management Project identified the difference in the ecosystem from groundfish to aquatic species and invertebrates in its first Ecosystem Status Report for the Eastern Scotian Shelf. ( Aquarone & Adams n.d ) point to a progressive paradigm change in ocean management exemplified with explicit recognition of all ocean sectors' effects on the marine environment, both individually and collectively. To achieve ecosystem-based control, the authors propose adaptive strategy management that includes conceptual and practical management objectives. Pollock, Cod, white hake, halibut, silver hake, and turbot are among the commercially exploited fish. Atlantic herring and pelagic fish and Atlantic mackerel fish. Snow crab, northern shrimp, and shortfin squid are examples of invertebrates. Both snow crab and north shrimp enjoy cold weather, and their increased landings correlate with the eastern seaboard's cooling. Nova Scotian Shelf. The most consistent knowledge about this LME is systematic shelf fishery surveys conducted between the 1960s and the present. Total registered landings on the Scotian Shelf LME peaked at 889,000 tonnes in 1970 and dropped to less than a quarter of that in 2004, at 213,000 tonnes ( Aquarone & Adams n.d ). Landings of Cod, silver hake, and redfish have all decreased dramatically. Thus overfishing is a significant challenge that significantly contributes to the food security problem on the Scottian Shelf. 

Due to the increase in value commanded by its crustacean landings, the recorded landings stood at a peak high of US$1.2 billion in the year 2000. In the mid-1970s, the primary production needed to maintain the recorded landings in this LME was higher than observed primary production, but this has decreased in recent years. The fantastic high PPR reported in the mid-1970s was most likely due to the harvesting of cod stocks' increased biomass than the annual surplus production. Activities of several commercially exploited fish species have seen a significant decline in abundance and scale, suggesting reaching exploitation limits (Teh et al.,2017) . There was the experiencing of eastern and western shelves leading to a reduction in size due to fishing efforts. In addition, the development of Canada's EEZ in 1977 resulted in a rapid increase in fishing effort. Recent studies of improvements in the productivity and biomass production of the Scotian Shelf LME have exposed the impacts of removing predators on the ecosystem's tropic structure. From the mid-1980s to the mid-1990s, the most significant shift in biomass production was a dramatic drop in groundfish and biomass. The crawlable demersal biomass had decreased from 450,000 tons in 1973 to less than 15,000 tons in 1997 (Nanninga & Berumen, 2014) . Pelagic fish, shrimp, and snow crab populations all increased in tandem with the decline. Increases in phytoplankton based on color index values from CPR were observed for forty years from 1960 to 2000 at the lower trophic stages and a rise in the number of zooplankter's reduction 2 mm in length. There is centering of the central fisheries on pelagic fish and macroinvertebrates, with herring, shrimp, and snow crab dominating ( Weatherdon et al., 2016 ). To counter the overexploitation of the LME's key fisheries, the implementation of a management scheme takes into account species interaction and biomass production like Cod, haddock, flounder, and other demersal fish. As a result of the destruction of various fish species, overfishing resulted in many fishery closures many years ago. 

Challenge of climatic changes resulting ecological effects 

The annual cycle of surface heating and other air-sea fluxes, combined with seasonal changes in the inflow of relatively fresh water from upstream, results in pronounced seasonal variation in temperature, salinity, and stratification in the Scotian Shelf's upper 100 m. Natural variability on time scales ranging from hours to decades is also present due to changes in the competing forces listed above. A raw mode of variability in big-scale atmospheric pressure and wind movements over the North Atlantic. With monthly to multi-decadal time scale fluctuations, it has affected various oceanographic properties off the coast of Atlantic Canada. These factors include the Gulf Stream's north-south direction and the amount of subpolar slope water extending west across the Grand Bank's Tail, both of which affect temperature and salinity over the Scotian Shelf. Owing to the decreased contribution of subpolar slope water, successive years of positive wintertime NAO anomalies result in cooler water over the Labrador. Then Newfound land Shelves and touching the eastern Scotian Shelf on the one side, and warm subtropical slope water penetrating the central and western Scotian Shelf at a depth on the other. 

The Atlantic Multi-decadal Oscillation (AMO) is a second natural means of variability that impacts the Scotian Shelf. It is an out-of-phase fluctuation of sea temperature in the northern and southern sections of the North Atlantic with resembling periodicities. The AMO's mechanisms are still being uncovered, with one theory linking it to a hemispheric-scale atmosphere-ice-ocean interaction involving the North Pacific and Arctic. Others suggest it is related to shifts in the Atlantic Meridional Overturning Circulation (AMOC) (Loder, 2012). The Atlantic portion of the so-called global ocean "conveyor belt," which regulates the Earth's overall climate system, is the AMOC. A linkage of AMOC variability also has to the Gulf Stream's north-south location and, as a result, temperature and fish distributions on the Scotian shelf between Cape Hatteras and the Gulf of Maine (Martin et al.,2014). Suggesting that the AMOC, NAO, and AMO factors on the Scotian Shelf may have a relationship. The temperature and acidity of the oceans will rise as the overlying atmosphere warms and carbon dioxide (CO2) concentrations rise. Because of the direct effect of local air-sea fluxes, the addition should be most significant. Still, they should also be at all depths over the shelf, and upper slope as waters ventilated elsewhere and earlier moved into the area ( Loder,2012) . Increased ocean acidity will reduce calcium carbonate concentration in the upper ocean, impacting calcareous species and the rest of the ecosystem components. There is also reason to believe that there would be more link to ocean warming at a lower confidence level. It is focused on the predicted slowing of the AMOC and the potential for more optimistic NAO abnormalities as the atmospheric polar vortex intensifies. High salinity in the slope waters off the Scotian Shelf, increased regular warm slope water intrusions into the shelf, and possibly changes in chemical composition at depth, like nutrients and mixed oxygen (Flannery & Cinnéide 2012) . All this results from a northward shift in the boundary between subtropical and subpolar water in the western North Atlantic. 

Finally, the Scotian Shelf and its environs face several challenges. According to the research of Human Activities, pollution severely impacts the Scottian Shelf, which names illegal spills from vessels and discharges like the chronic introduction of oil from shipping ships underwater. Also, waste, chemical pollutants from boats, and hydrocarbon extraction events are significant ongoing environmental issues, introducing invasive species and pathogens through ballast water. The value of recorded landings peaked in 2000 US dollars 2000, indicating a substantial decrease in silver hake cod and redfish landings due to the high value commanded by its crustacean landings. Both the eastern and western shelves saw a reduction in size due to fishing effort. Finally, climate change is a significant problem. The annual cycle of surface heating and other air-sea fluxes, combined with seasonal changes in the inflow of relatively fresh water from upstream, results in pronounced seasonal variation in temperature, salinity, and stratification in the Scotian Shelf. Thus stringent action needs to be taken to tackle such menace. 

References 

Aquarone, M. C., & Adams, S. XIX-60 Scotian Shelf: LME# 8. 

Dever, M., Hebert, D., Greenan, B. J. W., Sheng, J., & Smith, P. C. (2016). Hydrography and coastal circulation along the Halifax Line and the connections with the Gulf of St. Lawrence.  Atmosphere-Ocean ,  54 (3), 199-217. 

Flannery, W., & Ó Cinnéide, M. (2012). Deriving lessons relating to marine spatial planning from Canada's eastern Scotian shelf integrated management initiative.  Journal of Environmental Policy & Planning ,  14 (1), 97-117. 

Loder, J. (2012). Climate change on the Scotian Shelf: Recent variability and a future outlook.  Application of ecosystem research results (ERI) to fishery management. Sous la direction de R. Claytor et S. Leslie. DFO Can. Sci. Advis. Sec. Sci. Resp ,  62 , 10-25. 

Martin, B., Kowarski, K., Mouy, X., & Moors-Murphy, H. (2014, September). Recording and identification of marine mammal vocalizations on the Scotian shelf and slope. In  2014 Oceans-St. John's  (pp. 1-6). IEEE. 

Nanninga, G. B., & Berumen, M. L. (2014). The role of individual variation in marine larval dispersal.  Frontiers in Marine Science ,  1 , 71. 

Teh, L. S., Cheung, W. W., & Sumaila, U. R. (2017). Scenarios for investigating the future of Canada's oceans and marine fisheries under environmental and socioeconomic change.  Regional Environmental Change ,  17 (3), 619-633. 

Weatherdon, L. V., Magnan, A. K., Rogers, A. D., Sumaila, U. R., & Cheung, W. W. (2016). Observed and projected impacts of climate change on marine fisheries, aquaculture, coastal tourism, and human health: an update.  Frontiers in Marine Science ,  3 , 48.