Marine Biology - Lec 2

• Outgassing - that under the high pressures found in the Earth’s interior, gases remain dissolved in magma. As these magmas rise to the surface through volcanic activity, the pressure is reduced, and the gases are released.
• Volcanic activity releases many different gases, including water vapor, carbon dioxide (CO2), sulfur dioxide (SO2), carbon monoxide (CO), hydrogen sulfide (H2S), hydrogen gas, nitrogen, and methane (CH4).
• Lighter gases such as hydrogen and helium dissipated into space
• heavier gases remained and formed Earth’s early atmosphere, and potentially surface water
• Another theory is that water was brought to Earth through comets
• The composition of the ocean offers some clues as to its origin.
• Comets cannot have delivered all the water in the earth's oceans because the ice in the comets contains twice as many atoms of deuterium (a heavy isotope of hydrogen) to each atom of ordinary hydrogen as we find in seawater.
• Meteorites could not have delivered all of the water, because then the earth's atmosphere would contain nearly 10 times as much xenon (an inert gas) as it actually does.
• Meteorites carry this excess xenon.
• A mixture of meteoritic water and cometary water would not work either, because this combination would still contain a higher concentration of deuterium than is found in the oceans.
• combination of water derived from comets and water that was caught up in the rocky body of the earth as it formed.
• Water is in constant motion.
• Ocean - contains 97 % of Earth's known water supply
• Atmosphere - holds merely 0.001 %, or 3.05 mi3 (12.7 km3), of Earth's water. This reservoir is the primary means of moving water great distances, particularly far inland
• Cryosphere - The part of the Earth that is covered by ice and snow.
• Land - water on and beneath the land. This crucial source makes up the majority of what is known as "available water“ - water that can be easily tapped for human use.
• Lithosphere - Earth's crust and mantle, contains a vast, but unknown amount of water. This takes two forms: "free" water in cracks and pores, and chemically bound water – hydrated minerals formed in the presence of water and that contain hydrogen and oxygen.
• Water is the only natural substance that can exist as a solid, liquid,or gas.
• Water is also the "universal solvent," capable of dissolving more substances than any other liquid.
• One Sverdrup (Sv) is a flow rate of 1 million cubic meters, or 264 million gallons, per second.
• Currents & circulation - winds create surface currents, such as the Gulf Stream which ranges from 30 to 150 Sv.
• Ocean evaporation - evaporation over the ocean is 85 %of the global total.
• Ocean precipitation - more than three-quarters of global precipitation occurs over the ocean, a flow of water equal to between 10 and 13.4 Sv.
• Evapotranspiration - evapotranspiration combines evaporation (liquid water changing to vapor) and transpiration (water released by plants).
• Land precipitation - less than one-quarter of global precipitation occurs over land.
• Sublimation - under certain conditions, water can change directly from a solid (snow and ice) into a gas (water vapor) without melting.
• Wind transport - winds move water vapor and heat energy long distances across the face of Earth in a relatively short period of time.
• Groundwater - water flowing from the surface of the land into the ground forms groundwater, one of the most important and least renewable, water resources on Earth.
• Human use - agriculture currently accounts for 70 % of water use worldwide, 22 % is used by industry, and 8 % is consumed as drinking water.
• Rivers and runoff - rivers carry sediment, nutrients and other materials, making them an important link between land and ocean.
• Hydrothermal vents - in some places, water seeping into the seafloor is heated by magma. Some of the hot water reacts with rocks to form hydrated minerals; some rises back to the seafloor at hydrothermal vents, carrying with it chemicals and trace elements that mix into the ocean.
• Subduction - hydrated minerals, which contain chemically bound water, are carried beneath the seafloor at subduction zones, where the material is recombined into the crust and mantle.
• Volcanoes - volcanic eruptions release large amounts of steam into the atmosphere