Hadley cells extreme wet weather at equator and

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Hadley cells – extreme wet weather at equator, and extreme aridity around deserts - Polar cells – least well – defined - Doldrums Ocean Zones Epipelagic: (top surface layer) – “photic zone” – interacts with wind, waves, radiation – tens of m in open ocean, less at coastal margins Thermocline: exists at the bottom of the epipelagic layer Pelagic: open water (neritic, oceanic) Stratification: less dense (warmer, less salty or both), more dense (cooler, more salty or both), ~35g inorganic salts/kg sea water – varies with latitude and depth Ocean Currents - Driven by winds, water density, tides and water temperature - Coriolis effect - Where they are located, which direction they move, and how fast they move can all be affected by coastal and sea floor features - Surface currents: global wind systems and heating of surface water- help drive currents at large spatial and temporal scales - Deep current: differences in water density – salinity and temperature differences - Heat is transferred from tropics to polar regions – influences climate at local and global scales – thermohaline circulation - In cold regions eg north atlantic ocean, ocean water loses heat to atmosphere (more cold and dense) – water freezing adds more salt to the surrounding seawater – surface water flows in behind it, which in turn follows the same pattern - Critical part of earth’s climate system as well as ocean nutrient and carbon dioxide cycles eg gulf stream - North Atlantic Ocean (near the Greenland and Norwegian Seas) and the Antartic Ocean (near the Weddell Sea) – prime spots for density-induced downwelling – drives thermohaline circulation - North Atlantic thermohaline circulation has many effects on weather patterns and events. Linked with North Atlantic Oscillation (NAO) – multi-decadal oscillation in pressure (or sea surface temperature) El Nino and La Nina - Associate with variations in the tropical Pacific Ocean’s walker circulation and significant fluctuations in atmospheric pressure (the southern oscillation_, which influences the Walker Pattern - They are opposite phases of the El Nino – Southern oscillation (ENSO) – the combination of atmospheric (Southern Oscillation) and oceanic effects (el nino and la nina) - Sometimes the atmosphere shifts but the tropical pacific ocean doesn’t respond or vice versa – however, when they evolve in sync, el nino or la nina occur
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- Occur every 2-7 years but el nino more frequent – both typically last 9-12 months El Nino - “normal” east-to-weast surface trade winds across the tropical Pacific tend to weaken during El Nino – warm water can then shift toward the eastern tropical pacific - The warm water enables the development of showers and thunderstorms eastward – resulting atmospheric circulations tend to weaken trade winds further - Positive feedbacks critical for development of El Nino and La nina - Warmer than average temperatures over western and central Canada and over the western and northern united states -
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