Gitai Yahel (Yahel@Ruppin. ac Gitai Yahel (Yahel@Ruppin.ac.il) The School of Marine Sciences and Marine Environment Ruppin Academic Center, Chemical Oceanography.

Gitai Yahel (Yahel@Ruppin. ac
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Chemical Oceanography - 04 Introduction to the Physics and Biology of the Ocean The School of Marine Sciences and Marine Environment Ruppin Academic Center Gitai Yahel Tel.(09) #110, Skype gitaiyahel, Web

The vertical structure of the ocean
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, The vertical structure of the ocean Aphotic Deepsea ~3.8 km Thermocline Epipelagic zone illuminated, warm, productive nutrient depleted, saline, m Thermocline, nutricline, below m Permanent thermocline The ocean interior (90% of the ocean volume) Deep Cold Dark Stable Low biological activity Station 230, East Atlantic, 1 Nov 1974, MedAtlas Saturday, March 25, 2017

Schematic organization chart
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Schematic organization chart Type your text here Template for download in web site Polar zone Surface Ocean Type your text here Type your text here Type your text here Ocean interior Type your text here Type your text here Type your text here Type your text here Sediment Saturday, March 25, 2017

Example - Ocean density scheme
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Example - Ocean density scheme Sun light is the fundamental driver of the ocean density structure and circulation Polar zone Surface Ocean Lower density (warm but many times saltier) Large variations Strong horizontal currents Deep water formation Intense mixing Winter cooling storms Eddy diffusivity Ocean interior Upwelling in specific zones Wind driven (Ekman) Winter cooling storms Eddy diffusivity Higher density Deep water are very cold >4ºC and salty Relatively uniform Slow currents Winter cooling storms Eddy diffusivity Ultimately all energy dissipate into heat via friction (some with boundaries) Sediment Saturday, March 25, 2017

Nomenclature of oceanic zones
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Nomenclature of oceanic zones The continental margin regions are the transition zones between the continents and ocean basins. The major features at ocean margins are shown schematically in Fig. 1- 5. Though the features may vary, the general features shown occur in all ocean basins in the form of either two sequences: shelf-slope-rise-basin or shelf-slope-trench-basin. Fig 1-5 Schematic Diagram of Continental Margins The continental shelf is the submerged continuation of the adjacent land, modified in part by marine erosion or sediment deposition. The seaward edge of the continental shelf can frequently be clearly seen and it is called the shelf break. The shelf break tends to occur at a depth of about 200 m over most of the ocean. Sea level was almost 125m lower during Pleistocene glacial maxima. At those times the shoreline was close to the edge of present continental shelf, which was then a coastal plain. On average, the continental shelf is about 70 km wide, although it can vary widely (compare the east coast of China with the west coast of Peru). The Arctic Ocean has the largest proportion of shelf to total area of all the world’s oceans. The continental slope is characterized as the region where the gradient of the topography changes from 1:1000 on the shelf to greater than 1:40. Thus continental slopes are the relatively narrow, steeply inclined submerged edges of the continents. The continental slope may form one side of an ocean trench as it does off the west coast of Mexico or Peru or it may grade into the continental rise as it does off the east coast of the U.S. The ocean trenches are the topographic reflection of the subduction of oceanic plates beneath the continents. The greatest ocean depths occur in such trenches. The deepest is the Challenger Deep which descends to 11,035 meters in the Marianas Trench. The continental rises are mainly depositional features that are the result of coalescing of thick wedges of sedimentary deposits carried by turbidity currents down the slope and along the margin by boundary currents. Deposition is caused by the reduction in current speed when it flows out onto the gently sloping rise. Gradually the continental rise grades into the ocean basins and the abyssal plains. Saturday, March 25, 2017

Water cycle, major reservoirs and fluxes
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Water cycle, major reservoirs and fluxes Water is present on Earth in three phases - solid, liquid and gas. The ocean contains the bulk (97%) of the earth's water (1.37 x 109 km3 or about 1.37 x 1024 g) and moderates the global water cycle. Glaciers are the second largest reservoir with about 2% of the total. The distribution of the mass of water, is about 80% in the ocean and about 20% as pore water in sediments and sedimentary rocks. The reservoir of water in rivers, lakes and the atmosphere is a trivial part of the total (0.003%). A summary of the water reservoirs is given in Table 1-3 (after Reeburgh, 1997; Berner and Berner, 1987). Water is continually moving between reservoirs as part of the global hydrological cycle. These fluxes are summarized in Table 1-4. Evaporation exceeds precipitation over the ocean, while precipitation exceeds evaporation over land. River flow from land to the ocean accounts for the difference. There are important differences for the water fluxes in the different ocean basins. For example, there is net evaporation of fresh water from the Atlantic which is transported to the Pacific. Variability in this transport is important for understanding climate change. The ocean has a turnover time of about 37,000 years (1.37 x 109 km3 ÷ 37.4 km3 yr-1) with respect to river inflow. This is how long it would take to fill the ocean if it were totally dry. Turnover times are defined as the mass in the reservoir divided by the input or removal. By comparison the average residence time of water in the atmosphere with respect to evaporation from the oceans and continents is only about 10 days (1.3 x 104 km3 ÷ x 104 km3 yr-1). The ocean's role in controlling the water content of the atmosphere has important implications for past, present and future climates of the Earth. Water vapor itself is the most important greenhouse gas and, alone, is responsible for about 23°C of greenhouse warming. Without any greenhouse gases the average earth temperature would be 260°K (or - 3°C). Instead it averages 283°K (or 10°C) because of the trapping of infrared radiation by water vapor. Water's unusually high heat capacity and latent heat of evaporation play an important role in heat storage and transport, thus we need to learn about the physical properties of water and ionic solutions in chemical oceanography. One of the possible positive feedbacks of global warming will be increased atmospheric water content resulting from warming of the sea surface. One of the possible triggers for rapid climate change in the past may have been changes in the water budget for the Atlantic. Saturday, March 25, 2017

Surface Sea Temperature distribution
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Surface Sea Temperature distribution The sun is the major source of energy to the ocean Heat redistribution derive the global circulation Saturday, March 25, 2017

An animation of average Sea Surface Temperature
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, An animation of average Sea Surface Temperature NASA: The oceans of the world are heated at the surface by the sun, and this heating is uneven for many reasons. The Earth's axial rotation, revolution about the sun, and tilt all play a role, as do the wind-driven ocean surface currents. The first animation in this group shows the long-term average sea surface temperature, with red and yellow depicting warmer waters and blue depicting colder waters. The most obvious feature of this temperature map is the variation of the temperature by latitude, from the warm region along the equator to the cold regions near the poles. Another visible feature is the cooler regions just off the western coasts of North America, South America, and Africa. On these coasts, winds blow from land to ocean and push the warm water away from the coast, allowing cooler water to rise up from deeper in the ocean. The heat of the sun also forces evaporation at the ocean's surface, which puts water vapor into the atmosphere but leaves minerals and salts behind, keeping the ocean salty. The salinity of the ocean also varies from place to place, because evaporation varies based on the sea surface temperature and wind, rivers and rain storms inject fresh water into the ocean, and melting or freezing sea ice affects the salinity of polar waters. The second animation in this group shows the long term average sea surface salinity, where white regions have the highest salinity and dark regions the lowest. Notice the higher salinity in the Atlantic, due partly to salty water coming from the Mediterranean, and the lower salinity at the mouths of major rivers. The average density of sea surface water can be calculated from the average sea surface temperature and salinity using the state equation for seawater. The third animation shows the long term average sea surface density, with light blue regions having the least density and dark blue regions having the greatest density. The sea surface density variations are actually very small, less than 3% overall, but the variation is very important. There are three stable, dense regions in the ocean's surface, one in the sea around Iceland, Greenland, and Scandinavia and the other two near or under major Antarctic ice shelves. In these regions, the surface water becomes dense enough to sink and join the deep ocean currents. In fact, this sinking is thought to drive these deep currents as part of a system called the Thermohaline Circulation (see the animation The Thermohaline Circulation - The Great Ocean Conveyor Belt). This circulation has a strong effect on the Earth's climate, influencing the Gulf Stream, El Niño events, and both past and future Climate Shifts. The link between ocean temperature, salinity, and density also has other consequences. Research shows that over the past few decades, vast regions of abnormal sea surface salinity - called Great Salinity Anomalies - have propagated around the far north Atlantic, impacting local ecosystems and the sinking of water masses. At mid-latitudes, salinity influences the depth to which water masses sink and how far they extend through the ocean. The location and depth of these water masses controls how heat and salt are transported between the tropics and high latitudes. Like atmospheric fronts that bring unstable weather, ocean fronts found at the interface between water masses are areas of high activity often correlated with important fisheries such as tuna. In the tropics, sea surface salinity is primarily controlled by rainfall and river runoff; these sources of freshwater regulate how the oceans interact with the atmosphere. Affecting almost half of the world's human population each year, monsoons are driven by exchanges at the air-ocean boundary. Likewise, El Niño has profound effects on humankind and is, to an unknown extent, governed by ocean salinity. In fact, recent studies indicate that understanding salinity's effect on upper ocean buoyancy may be the key to better El Niño forecasts. The long term averages (or "climatologies") of sea surface temperature and salinity used in these animations come from the World Ocean Atlas 2005 (WOA2005) NASA: Saturday, March 25, 2017

Latitudinal precipitation and salinity distribution
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Latitudinal precipitation and salinity distribution Surface seawater salinities largely reflect the local balance between evaporation and precipitation. Surface seawater salinities largely reflect the local balance between evaporation and precipitation. a. Low salinities occur near the equator due to rain from rising atmospheric circulation. b. High salinities are typical of the hot dry gyres flanking the equator (20-30° latitude) where atmospheric circulation cells descend. c. Salinity can also be affected by sea ice formation/melting (e.g. around Antarctica) d. The surface N. Atlantic is saltier than the surface N. Pacific, making surface water denser in the N. Atlantic at the same temperature and leading to down-welling of water in this region this difference is because on average N. Atlantic is warmer (10.0 C) than N. Pacific (6.7 C). This is mostly because of the greater local heating effect of the Gulf Stream, as compared to the Kuroshio Current. Warmer water evaporates more rapidly, creating a higher residual salt content. The influence of surface fluctuations in salinity due to changes in evaporation and precipitation is generally small below 1000 m, where salinities are mostly between about 34.5 and 35.0 at all latitudes. Zones where salinity decreases with depth are typically found occur at low latitudes and mid latitudes, between the mixed surface layer and the deep ocean. These zones are known as haloclines. Saturday, March 25, 2017

Global salinity distribution
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Global salinity distribution Ocean Salinity is fairly constant Saturday, March 25, 2017

Average Sea Surface Salinity
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Average Sea Surface Salinity NASA: The heat of the sun also forces evaporation at the ocean's surface, which puts water vapor into the atmosphere but leaves minerals and salts behind, keeping the ocean salty. The salinity of the ocean also varies from place to place, because evaporation varies based on the sea surface temperature and wind, rivers and rain storms inject fresh water into the ocean, and melting or freezing sea ice affects the salinity of polar waters. The second animation in this group shows the long term average sea surface salinity, where white regions have the highest salinity and dark regions the lowest. Notice the higher salinity in the Atlantic, due partly to salty water coming from the Mediterranean, and the lower salinity at the mouths of major rivers. The average density of sea surface water can be calculated from the average sea surface temperature and salinity using the state equation for seawater. The third animation shows the long term average sea surface density, with light blue regions having the least density and dark blue regions having the greatest density. The sea surface density variations are actually very small, less than 3% overall, but the variation is very important. There are three stable, dense regions in the ocean's surface, one in the sea around Iceland, Greenland, and Scandinavia and the other two near or under major Antarctic ice shelves. In these regions, the surface water becomes dense enough to sink and join the deep ocean currents. In fact, this sinking is thought to drive these deep currents as part of a system called the Thermohaline Circulation (see the animation The Thermohaline Circulation - The Great Ocean Conveyor Belt). This circulation has a strong effect on the Earth's climate, influencing the Gulf Stream, El Niño events, and both past and future Climate Shifts. The link between ocean temperature, salinity, and density also has other consequences. Research shows that over the past few decades, vast regions of abnormal sea surface salinity - called Great Salinity Anomalies - have propagated around the far north Atlantic, impacting local ecosystems and the sinking of water masses. At mid-latitudes, salinity influences the depth to which water masses sink and how far they extend through the ocean. The location and depth of these water masses controls how heat and salt are transported between the tropics and high latitudes. Like atmospheric fronts that bring unstable weather, ocean fronts found at the interface between water masses are areas of high activity often correlated with important fisheries such as tuna. In the tropics, sea surface salinity is primarily controlled by rainfall and river runoff; these sources of freshwater regulate how the oceans interact with the atmosphere. Affecting almost half of the world's human population each year, monsoons are driven by exchanges at the air-ocean boundary. Likewise, El Niño has profound effects on humankind and is, to an unknown extent, governed by ocean salinity. In fact, recent studies indicate that understanding salinity's effect on upper ocean buoyancy may be the key to better El Niño forecasts. The long term averages (or "climatologies") of sea surface temperature and salinity used in these animations come from the World Ocean Atlas 2005 (WOA2005) NASA: Saturday, March 25, 2017

Regional thermocline structure
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Regional thermocline structure Tropics Sarmiento and Gruber 2005 Chapter2a Saturday, March 25, 2017

Seasonal thermocline dynamics at mid latitudes
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Seasonal thermocline dynamics at mid latitudes Sarmiento and Gruber 2005 Chapter2a Saturday, March 25, 2017

General circulation – surface currents
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, General circulation – surface currents The great gyres are the most prominent feature of the surface circulation Surface Currents Surface ocean currents respond primarily to the climatic wind field. The prevailing winds supply much of the energy that drives surface water movements. This becomes clear when charts of the surface winds and ocean surface currents are superimposed. The wind-driven circulation occurs principally in the upper few hundred meters and is therefore primarily a horizontal circulation, although vertical motions can be induced when the geometry of surface circulation results in convergences (down-welling) or divergences (upwelling). The depth to which the surface circulation penetrates is dependent on the water column stratification. In the equatorial region the currents extend to m, while in the circumpolar region where stratification is weak the surface circulation can extend to the sea floor. The net direction of motion of the water is not always the same as the wind, because other factors come into play. The wind blowing across the sea surface drags the surface along and sets this thin layer in motion. The surface drags the next layer and the process continues downward, involving successively deeper layers. As a result of friction between the layers each deeper layer moves more slowly than the one above and its motion is deflected to the right (clockwise) in the northern hemisphere by the Coriolis force. If this effect is represented by arrows (vectors) whose direction indicates current direction and length indicates speed, the change in current direction and speed with depth forms a spiral. This feature is called an Ekman spiral. Ekman transport, changes in sea surface topography and the Coriolis force combine to form geostrophic currents. In the North Pacific for example the Westerlies at ~40°N and the Northeast trades (~10°N) set the North Pacific Current and North Equatorial Current in motion as a circular gyre. Because of the Ekman drift, surface water is pushed toward the center of the gyre (~25°N) and piles up to form a sea surface "topographic high". As a result of the elevated sea surface, water tends to flow "downhill" in response to gravity. As it flows, however, the Coriolis force deflects the water to the right (in the northern hemisphere). When the current is constant and results from balance between the pressure gradient force due to the elevated sea surface and the Coriolis force, the flow is said to be in geostrophic balance. The actual flow is then nearly parallel to the contours of the elevated sea surface and clockwise. As a result of these factors, wind, Ekman transport, Coriolis force, the surface ocean circulation in the mid latitudes is characterized by clockwise gyres in the northern hemisphere and counterclockwise gyres in the southern hemisphere. The regions where Ekman transport tends to push water together, such as the subtropical gyres, are called convergences. Divergences, such as the equator, result when surface waters are pushed apart. Where water diverges there is upwelling and where it converges, downwelling (Thurman, 1990). This circulation has important consequences for chemical oceanography because regions of upwelling (near the continental margins and at the equator) are locations of high nutrient content in the surface waters and locations of downwelling (the subtropical gyres) are locations of very low nutrient concentration. Total transport by the surface currents varies greatly and reflects the mean currents and cross sectional area. Some representative examples will illustrate the scale. The transport around the subtropical gyre in the North Pacific is about 70 Sv (1 Sv = 1 x 106 m3s-1). The Gulf Stream, which is a major northward flow off the east coast of North America, increases from 30 Sv in the Florida Straits to 150 Sv at 64°30'W, or 2000 km downstream. Saturday, March 25, 2017

General circulation – surface currents
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, General circulation – surface currents Surface Currents Surface ocean currents respond primarily to the climatic wind field. The prevailing winds supply much of the energy that drives surface water movements. This becomes clear when charts of the surface winds and ocean surface currents are superimposed. The wind-driven circulation occurs principally in the upper few hundred meters and is therefore primarily a horizontal circulation, although vertical motions can be induced when the geometry of surface circulation results in convergences (down-welling) or divergences (upwelling). The depth to which the surface circulation penetrates is dependent on the water column stratification. In the equatorial region the currents extend to m, while in the circumpolar region where stratification is weak the surface circulation can extend to the sea floor. The net direction of motion of the water is not always the same as the wind, because other factors come into play. The wind blowing across the sea surface drags the surface along and sets this thin layer in motion. The surface drags the next layer and the process continues downward, involving successively deeper layers. As a result of friction between the layers each deeper layer moves more slowly than the one above and its motion is deflected to the right (clockwise) in the northern hemisphere by the Coriolis force. If this effect is represented by arrows (vectors) whose direction indicates current direction and length indicates speed, the change in current direction and speed with depth forms a spiral. This feature is called an Ekman spiral. Ekman transport, changes in sea surface topography and the Coriolis force combine to form geostrophic currents. In the North Pacific for example the Westerlies at ~40°N and the Northeast trades (~10°N) set the North Pacific Current and North Equatorial Current in motion as a circular gyre. Because of the Ekman drift, surface water is pushed toward the center of the gyre (~25°N) and piles up to form a sea surface "topographic high". As a result of the elevated sea surface, water tends to flow "downhill" in response to gravity. As it flows, however, the Coriolis force deflects the water to the right (in the northern hemisphere). When the current is constant and results from balance between the pressure gradient force due to the elevated sea surface and the Coriolis force, the flow is said to be in geostrophic balance. The actual flow is then nearly parallel to the contours of the elevated sea surface and clockwise. As a result of these factors, wind, Ekman transport, Coriolis force, the surface ocean circulation in the mid latitudes is characterized by clockwise gyres in the northern hemisphere and counterclockwise gyres in the southern hemisphere. The regions where Ekman transport tends to push water together, such as the subtropical gyres, are called convergences. Divergences, such as the equator, result when surface waters are pushed apart. Where water diverges there is upwelling and where it converges, downwelling (Thurman, 1990). This circulation has important consequences for chemical oceanography because regions of upwelling (near the continental margins and at the equator) are locations of high nutrient content in the surface waters and locations of downwelling (the subtropical gyres) are locations of very low nutrient concentration. Total transport by the surface currents varies greatly and reflects the mean currents and cross sectional area. Some representative examples will illustrate the scale. The transport around the subtropical gyre in the North Pacific is about 70 Sv (1 Sv = 1 x 106 m3s-1). The Gulf Stream, which is a major northward flow off the east coast of North America, increases from 30 Sv in the Florida Straits to 150 Sv at 64°30'W, or 2000 km downstream. Saturday, March 25, 2017

Upwelling zones The deep water that surfaces in upwelling is cold; by looking at Sea Surface Temperature maps we can identify cool upwelled water versus hotter surface water.

Equatorial Upwelling Water Flow s Upwelling

Coastal Upwelling

Schematic of thermohaline circulation.
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Schematic of thermohaline circulation. Sinking Saturday, March 25, 2017

The Thermohaline Circulation – The Great Ocean Conveyor Belt
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, The Thermohaline Circulation – The Great Ocean Conveyor Belt The oceans are mostly composed of warm salty water near the surface over cold, less salty water in the ocean depths. These two regions don't mix except in certain special areas. The ocean currents, the movement of the ocean in the surface layer, are driven mostly by the wind. In certain areas near the polar oceans, the colder surface water also gets saltier due to evaporation or sea ice formation. In these regions, the surface water becomes dense enough to sink to the ocean depths. This pumping of surface water into the deep ocean forces the deep water to move horizontally until it can find an area on the world where it can rise back to the surface and close the current loop. This usually occurs in the equatorial ocean, mostly in the Pacific and Indian Oceans. This very large, slow current is called the thermohaline circulation because it is caused by temperature and salinity (haline) variations. This animation shows one of the major regions where this pumping occurs, the North Atlantic Ocean around Greenland, Iceland, and the North Sea. The surface ocean current brings new water to this region from the South Atlantic via the Gulf Stream and the water returns to the South Atlantic via the North Atlantic Deep Water current. The continual influx of warm water into the North Atlantic polar ocean keeps the regions around Iceland and southern Greenland mostly free of sea ice year round. The animation also shows another feature of the global ocean circulation: the Antarctic Circumpolar Current. The region around latitude 60 south is the the only part of the Earth where the ocean can flow all the way around the world with no land in the way. As a result, both the surface and deep waters flow from west to east around Antarctica. This circumpolar motion links the world's oceans and allows the deep water circulation from the Atlantic to rise in the Indian and Pacific Oceans and the surface circulation to close with the northward flow in the Atlantic. The color on the world's ocean's at the beginning of this animation represents surface water density, with dark regions being most dense and light regions being least dense (see the animation Sea Surface Temperature, Salinity and Density). The depths of the oceans are highly exaggerated to better illustrate the differences between the surface flows and deep water flows. The actual flows in this model are based on current theories of the thermohaline circulation rather than actual data. The thermohaline circulation is a very slow moving current that can be difficult to distinguish from general ocean circulation. Therefore, it is difficult to measure or simulate. This animation first depicts thermohaline surface flows over surface density, and illustrates the sinking of water in the dense ocean near Iceland and Greenland. The surface of the ocean then fades away and the animation pulls back to show the global thermohaline circulation. Saturday, March 25, 2017

North Atlantic circulation
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, North Atlantic circulation North Atlantic Deep Water (NADW) Sources: Greenland Sea (80%) and Labrador Sea (20%) Characteristics: Temperature of 2.5º C and salinity of 35.03 North Atlantic deep water forms as warm, saline waters from the Gulf Stream moves northward, cooled and become more dense. Saturday, March 25, 2017

The great global conveyor – simplified scheme
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, The great global conveyor – simplified scheme The Ocean Conveyor Belt The ocean conveyor-belt is one of the major elements of today’s ocean circulation system (Broecker, 1997). A key feature is that it delivers an enormous amount of heat to the North Atlantic and this has profound implications for past, present and probably future climates. The conveyor-belt is shown schematically in the figure below. Warm and salty surface currents in the western North Atlantic (e.g. the Gulf Stream) transport heat to the Norwegian-Greenland Seas where the heat is transferred to the atmosphere. The cooling increases the density of seawater resulting in formation of cold and salty water in the North Atlantic. This water sinks to depth and forms the North Atlantic Deep Water (NADW). The NADW travels south through the Atlantic and then joins the Circumpolar Current that travels virtually unimpeded in a clockwise direction around the Antarctic Continent. It is now believed that the major region of deep water formation is along the margins of Antartica (due to sea ice formation and cooling) that feeds the Circumpolar Current. The Weddell Sea, because of its very low temperature, is the main source of Antarctic Bottom Water (AABW), which flows northward at the very bottom into the South Atlantic, and then through the Vema Channel in the Rio Grande Rise into the North Atlantic. It ultimately returns southward as part of the NADW. The circumpolar current is a blend of waters of NADW (~47%) and Antarctic margin (~53%) origin. This current is the source of deep water to the Indian and Pacific Oceans. Deep water does not form in a similar way in the North Pacific because the salinity is too low (Warren, 1983). This deep water mass enters the Pacific in the southwest corner and flows north along the western boundary of the Tonga Trench. Saturday, March 25, 2017

The great global conveyor
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, The great global conveyor The Ocean Conveyor Belt The ocean conveyor-belt is one of the major elements of today’s ocean circulation system (Broecker, 1997). A key feature is that it delivers an enormous amount of heat to the North Atlantic and this has profound implications for past, present and probably future climates. The conveyor-belt is shown schematically in the figure below. Warm and salty surface currents in the western North Atlantic (e.g. the Gulf Stream) transport heat to the Norwegian-Greenland Seas where the heat is transferred to the atmosphere. The cooling increases the density of seawater resulting in formation of cold and salty water in the North Atlantic. This water sinks to depth and forms the North Atlantic Deep Water (NADW). The NADW travels south through the Atlantic and then joins the Circumpolar Current that travels virtually unimpeded in a clockwise direction around the Antarctic Continent. It is now believed that the major region of deep water formation is along the margins of Antartica (due to sea ice formation and cooling) that feeds the Circumpolar Current. The Weddell Sea, because of its very low temperature, is the main source of Antarctic Bottom Water (AABW), which flows northward at the very bottom into the South Atlantic, and then through the Vema Channel in the Rio Grande Rise into the North Atlantic. It ultimately returns southward as part of the NADW. The circumpolar current is a blend of waters of NADW (~47%) and Antarctic margin (~53%) origin. This current is the source of deep water to the Indian and Pacific Oceans. Deep water does not form in a similar way in the North Pacific because the salinity is too low (Warren, 1983). This deep water mass enters the Pacific in the southwest corner and flows north along the western boundary of the Tonga Trench. from Aguado and Burt, Understanding Weather & Climate Saturday, March 25, 2017

Implication for chemical oceanography
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Implication for chemical oceanography Distinct Horizontal distribution pattern of chemicals in the ocean – the ocean is NOT fully mixed! Mixing time 103 years Uneven distribution of chemicals due to: Salinity Removal (e.g. burial) Addition (e.g., rivers) Transformation (e.g., photosynthesis) Saturday, March 25, 2017

Biological oceanography - the major players:
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Biological oceanography - the major players: Grazers Primary producers Decomposers+ Saturday, March 25, 2017

Energy and mass transfer – we use a simplified scheme
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Energy and mass transfer – we use a simplified scheme Saturday, March 25, 2017

Energy Flow Saturday, March 25, 2017
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Energy Flow Saturday, March 25, 2017

Passage of energy between trophic levels
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Passage of energy between trophic levels Saturday, March 25, 2017

Bio-geo-chemical cycling - mass cycled, energy is wasted…(as heat)
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Bio-geo-chemical cycling - mass cycled, energy is wasted…(as heat) Saturday, March 25, 2017

Macro nutrients cycling
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Macro nutrients cycling Saturday, March 25, 2017

Mass balance and energy transfer
Gitai Yahel The School of Marine Sciences and Marine Environment Ruppin Academic Center, Mass balance and energy transfer Saturday, March 25, 2017

Gitai Yahel (Yahel@Ruppin. ac Gitai Yahel (Yahel@Ruppin.ac.il) The School of Marine Sciences and Marine Environment Ruppin Academic Center, Chemical Oceanography.

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