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Oceans and Climate Margaret Mayer, Diné College How the Sacred Element of Air Impacts the Oceans • Winds and Surface Currents (friction) • Moving Water influenced by the Coriolis Effect (Earth’s Rotation) • Atmospheric Circulation How the Sacred Element of Earth Impacts the Oceans • Trade winds produce westward flowing currents in the tropics that deflect north and south when they hit the western continents • Westerlies cause currents to flow eastward in the midlatitudes until they hit the eastern land masses where they deflect toward the poles or toward the equator. • The overall effect is a gyre. Coriolis Effect How the Sacred Element of Water Impacts the Oceans • Heat capacity – energy required to heat water (extremely high due to H-bonding) • Solid state of water is less dense than liquid water (ice floats) • Salt water is more dense than fresh water • Water remains a liquid over an extremely wide range of temperatures • Vertical composition of the ocean is driven by differences in salinity. How the Sacred Element of Fire Impacts the Oceans Oceans absorb and store large amounts of energy as heat. Oceans change temperature much more slowly than the atmosphere or land. SST – Sea Surface Temperature Vertical composition of the ocean is also driven by temperature Overall effect is called thermohaline circulation Hydrologic Cycle and Oceans • Oceans contain 97% of the water on Earth • Oceans receive 78% of all precipitation • Oceans evaporate 86% of all water to the • • atmosphere (salt remains behind) Oceans are key to transporting water (and heat) in large gyres from the equator to the poles and back to the equator Note: all wind and current patterns observed on the surface of the planet is the direct result of the uneven heating and uneven heat distribution of the earth’s surface by the sun. Global Warming and an Accelerated Hydrological Cycle • Evaporation rates increase with surface temperature – Loss of fresh water in equatorial areas • Precipitation increases as temperatures decrease (cold air holds less water) – Gain of fresh water in polar regions Natural Sources of Warming • Changes in solar output (our sun) • Volcanic activity(complex) • El Niño-Southern Oscillation (ENSO) – "It is scientifically inconceivable that - after changing forest into cities, putting dust and soot into the atmosphere, putting millions of acres of desert into irrigated agriculture, and putting greenhouse gases into the atmosphere - humans have not altered the natural course of the climate system." American Geophysical Union Shifts in Southern Oscillation (SO) El Nino vs La Nina Ocean Temps The Role of the Ocean in Climate • Stores most of the solar energy from the sun as heat (1000 times more than air but moves energy slower so air-ocean impacts similar) • Stores CO2 – (50% of carbon emissions) • Stores fresh water • Stores salt Great Ocean Conveyor Belt (GOC) a Heat Pump Driven by Thermohaline circulation What has or can stop the Heat Pump? • If surface waters in the north are no longer dense enough to sink – SST too warm to sink – Too much fresh water from • Melting ice • Increased precipitation • Little Ice Age – 700 years ago (1300 – 1800 AD) • Greenland Ice Sheet melts Changes in Salinity The record of recent climate changes Abrupt Climate Change Events The Younger Dryas—about 12,700 years ago, average temperatures in the North Atlantic region abruptly plummeted nearly 5°C and remained that way for 1,300 years before rapidly warming again. Believed to be caused by a huge influx of fresh water to the ocean. The Medieval Period—An abrupt warming took place about 1,000 years ago. It was not nearly so dramatic as past events, but it nevertheless allowed the Norse to establish settlements in Greenland. The Little Ice Age—The Norse abandoned their Greenland settlements when the climate turned abruptly colder 700 years ago. Between 1300 and 1850, severe winters had profound agricultural, economic, and political impacts in Europe. (R.B. Alley, from The Two-Mile Time Machine, 2000) Thought to be caused by sulfates from coal burning. Ocean/Air Temperature • Sea surface temperatures(SSTs) have risen during the • • last twenty years by 1-2 o F. As water has a much higher specific heat/heat capacity than air, this represents a major amount of heat added into the ocean when one also takes into account the surface area of the ocean versus the surface area of the continents. – Corals extremely temperature sensitive Air temperatures have risen on average 3-4 o F during the same period and are expected to rise even more up to 7 o F over the next century. Changes in jet stream patterns, weather patterns. Acidity of Oceans • When CO2 dissolves it forms a weak acid – CO2 + H2O H2CO3 carbonic acid • CaCO3 + Acid dissolves (demo) • pH scale as acidity increases, pH decreases • Lower pH is causing the shells of many marine organisms to dissolve including coral reefs. Oceanic Inverted Biopyramid • Most organisms are in the bottom phyla • Most organisms are endemic • Phytoplankton generate large amounts of oxygen • Phytos are eaten almost as soon as they add biomass to the system, hence the inverted biopyramid. Changes in Flora/Fauna • Overall – observed changes in species • • distribution. Seeing species typically found at temperate or tropical latitudes being found in subarctic latitudes – be it land or sea. Changes in phytoplankton distribution – Bering Sea and Gulf of Alaska – diatoms (cold water phytos) are being replaced by coccolithophorids (warm water phytos). This changes the entire dynamics of the Arctic oceanic food web. ”Belch from the deep” • Methane hydrates (solid, ice-like formations at the bottom of the oceans) • Methane is produced by bacteria in the ocean • Powerful greenhouse gas • If temperatures increase or pressure decreases this gas could be released in large quantities The Great Paradox • Could global warming lead to an ice age? • Added surface fresh water which reduces salinity • • (and thus density) can shut down the “Conveyor Belt” which is a major heat distribution mechanism for the planet. This change can occur (and has occurred) on the order of decades if not years. There is some indication this may have begun as researchers from Dalhousie University in Halifax, Nova Scotia have documented a slow down in the vertical sinking rate in the GINSEA. Assignment: • Draw the major ocean currents – Label cold and warm currents • Next, draw a 2nd sketch showing how those currents might be affected by climate change • One-page paper: discuss your sketches, and how the change in ocean currents might affect life on our planet.