The trouble with our times is that the future is not what it used to be The time for a finite world has started Paul Valery OCNG 251 Oceanography Thursday Sept 09 2008 The Hydrological Cycle Defining Boundaries 1 The Global Hydrological Cycle Reservoir Partition Fluxes Residence Time 2 Defining Boundaries 1 Marine Provinces Cycle Approach Some Definitions Transport and transformation processes within definite reservoirs Carbon Rock Water Cycles Reservoir box compartment M in mass units or moles An amount of material defined by certain physical chemical or biological characteristics that can be considered homogeneous O2 in the atmosphere Carbon in living organic matter in the Ocean Ocean Water in surface water masses Flux F The amount of material transferred from one reservoir to another per unit time per unit area The rate of evaporation of water from the surface Ocean The rate of deposition of inorganic carbon carbonates on marine sediments The rate of contaminant input to a lake or a bay Cycle Approach Source Q A flux of material into a reservoir Sink S A flux of material out of a reservoir Budget A balance sheet of all sources and sinks of a reservoir If sources and sinks balance each other and do not change with time the reservoir is in steady state M does not change with time If steady state prevails then a fllux that is unknown can be estimated by its difference from the other fluxes Turnover time time The ratio of the content M of the reservoir to the sum of its sinks S or sources Q The time it will take to empty the reservoir if there aren aren t any sources It is also a measure of the average time an atom molecule spends in the reservoir Cycle Cycle A system consisting of two or more connected reservoir where a large part of the material is transferred through the system in a cyclic fashion The Rock Cycle The Water Hydrologic Cycle The Water Cycle in detail The volume of water at the surface of the Earth is enormous 1 37 109 km3 total reservoir The Oceans cover 71 of the Earth Earth s surface 29 for the continent masses above sea level Reservoir Biosphere Volume km3 0 6 103 Rivers Atmosphere Lakes Groundwater Glacial and other land ice Oceanic water and sea ice Total Total 0 00004 1 7 103 13 103 125 103 9500 103 29000 103 0 0001 0 001 0 01 0 68 2 05 1 370 000 103 97 25 1 408 640 103 Adapted from Berner Berner The Global Water Cycle Prentice Hall 1987 100 Fluxes F in 103 km3 yr Of total yearly evaporation 84 evaporates from the Oceans and 16 from continental surfaces However return to the Earth surface via precipitation 75 falls directly on the Oceans and 25 on the continents During the year the atmosphere transports 9 of Oceans Oceans evaporation to the continents This water is returned via surface streams and as groundwater Errors Precipitation and evaporation are difficult to measure precisely over the oceans They are mostly estimated from models and satellite data Groundwater reservoir estimates bear a inherent error in the fact that they are indirectly determined Concept of residence time High probability that a certain fraction of the atoms or molecules forming the reservoir M will be of a certain age mean age of the element when it leaves the reservoir Inflow Q Outflow S Reservoir M Soil moisture and evapotranspiration rates depend on indirect measurements and average soil quality and global regional respiration rates In steady state Q S Residence time t M Q M S Residence Time years months weeks High probability that a certain fraction of the atoms or molecules forming the reservoir M will be of a certain age mean age of the element when it leaves the reservoir The simplified residence time turnover time The time it would take to empty a reservoir if the sink S remained constant while the source were zero 0 M S or M Q M 0S Residence Time Residence time of water in the atmosphere M S 0 M 13 103 km3 S 297 O 99 C 396 103 km3 yr 0 033 yr 12 days Replacement 30 times year 0 Residence time of water in the Oceans M S 0 M 1 370 000 103 km3 S 334 103 km3 yr evaporation 0 M S 4102 yrs Residence Time Residence Time Relative exchange times affect overall 0 The residence time of water in the atmosphere is very short The residence time of water in the Oceans is much longer If we consider that each year the upper 1 m meter of the Oceans Oceans surface evaporate and the Oceans have an average depth of 4000m the Oceans would completely evaporate in 4000 yr IF The Oceans had a completely uniform depth and no source What is the sink sink Because the water cycles through the atmosphere and is returned 4000 yr would be the time required to completely recirculate all Ocean water Residence Time In actuality because Ocean depths vary widely the residence time varies widely from place to place System Approach System Approach Isolated System System which boundaries prevent any exchange of matter and energy Closed System System which boundaries only allow exchange of energy but not of matter Open System System which boundaries allows any exchange of matter and energy Feedback All closed and open systems respond to inputs and have outputs A feedback is a specific output that serves as an input to the system Negative Feedback stabilizing The system system s response is in the opposite direction as that of the output CLOUDS System Approach System Approach Positive Feedback destabilizing The system system s response is in the same direction as that of the output Positive Feedback destabilizing CLOUDS Number of bacteria Bacteria in a bottle 1 4E 18 1 2E 18 1 0E 18 8 0E 17 6 0E 17 4 0E 17 Bottle half full 2 0E 17 0 0E 00 0 10 20 30 40 Time minutes 50 59 min 60 The Hydrosphere Oceans Distribution 71 of Earth Earth s surface is covered by Oceans About 70 of land masses occur in the Northern Hemisphere The Southern Hemisphere Water Hemisphere Ocean Atlantic Pacific Indian Total Area 106 km2 106 4 179 7 74 9 361 Volume 106 km3 354 7 723 7 291 9 1370 3 Mean Depth m 3332 4028 3897 3795 The Hypsographic Curve Only 20 of land areas 2 km 85 of the Oceans are 2 km Mean elevation of land 840 m Mean depth of Oceans 3795 m Highest 8840 m Deepest 11020 m Marine topography Ocean basins basins bottom topography is heterogeneous How deep is the Ocean How high the moon moon Bathymetry of the Oceans is variable i e Atlantic being shallow shallow vs Pacific Indian subdivisions into Continental Margins Deep ocean basins and Mid ocean ridges ridges The Marine Provinces The bottom of the Oceans can be divided into 3