The ocean basins are divided into three main Oceans: The Pacific Ocean is the largest and deepest (52% of the ocean area, mean depth of 4028 meters); The Indian Ocean (20% area, mean depth of 3897 m) and The Atlantic Ocean, the shallowest because of the rather narrow deep basins (25% area, mean depth of 3332 m). The Arctic is considered part of the Atlantic Ocean; The southern parts of the three Oceans are referred to as the Southern Ocean. The northern hemisphere has less ocean than the southern hemisphere, only about 61% ocean versus 81% for the southern hemisphere.

Freshwater: how strange! Polar molecule hydrogen bonding Water- a rather light molecule with strong bonds

cabelling 2°C 6°C Weights are the same: gr1h1=gr2h2 How much would sea level in a 4000 m freshwater ocean, fall if the 2 and 6°C reservoirs [r = 0.9998] were to mix completely to form a 4°C reservoir [r = 1.000]? Answer: about 80 cm Column 1 r=0.9998 Column 2 r=1.000 Consequence: Easy to freeze a lake cabelling 2°C 4° 6°C Balance beam 3° 5° gravity Weights are the same: gr1h1=gr2h2 sinking

Q = rCp Vol dT° 1 watt = 1 joule/sec 1 cal = 4.184 joules If V = 1 m3 and dT is 1°C Qair = (1.293)(1004) = 1,298 joules Qwater = (1023)(4218) = 4,315,014 joules [over 3000 times larger than air] So a little change of water temperature balanced by sea-air heat flux can really jolt the atmosphere. Same true if water phase change is linked to atmosphere temperature. You can play with the numbers.

Gulf Stream Hot “Warm-Pool” Cold, polar Upwelling of cool subsurface water Hot “Warm-Pool” Cold, polar

How salt alters the water properties Sea water is about a 3.49% salt solution [34.9 ppt], the rest is freshwater. The major salt constituent is Chloride [55%] and sodium [30.6%] How salt alters the water properties Is water colder than -2°C observed? Yes, at the base of glacial ice shelves of Antarctica. [melts at seawater Tf, why not 0°C?]

Ocean Salinity The more saline, the denser the sea water Sea water is about a 3.49% salt solution [34.9 ppt], the rest is freshwater. The major salt constituent is Chloride [55%] and sodium [30.6%] 1022 kg/m3 isopycnals The more saline, the denser the sea water Density of sea water is a function of temperature and salinity, both play an important role 1029 kg/m3 Ocean Salinity

atmosphere A B ocean E>P A P>E B

Stratification Waters warmer than 10°C dominate the sea surface but do not extend much below 500 m in the ocean; the warm waters provide just a veneer of warmth over a cold ocean. The sharp drop off in temperature with depth is called the thermocline. Deeper cold waters derive their properties at the sea surface during winter at high latitude.

Normal SST El Niño Fig. 18.

Ocean Stratification Take away ideas: 1. Water & Climate: The ocean extends over 70.8% of the earth's surface. The ocean holds 98% of the 1.4 billion cubic kilometers of water on the planet, divided within three major basins. The high capacity and density of water relative to the atmosphere, and the great amount of energy required for change of phase of water (solid - liquid - vapor) makes the ocean a powerful and stabilizing force of the Earth's climate system. One obvious consequence of the ocean’s influence is the “marine effect”, which acts to attenuate winter/summer and day/night extremes of air temperature. Another is that the ocean circulation transfers significant amount of heat from low to higher latitudes, helping the climate system to attain an approximate steady state condition. The ocean is a key part of the global hydrological cycle, providing moisture for the atmosphere; ocean circulation of freshwater balances the net evaporative and precipitation belts. 2. Sea Surface Temperature: The temperature of the sea surface is high (27-30°C) near the equator, often the maximum value is occurs a few degrees of latitude north of the equator and low (at the sea water freezing point of –1.9°C) within the polar oceans. However, there are also changes of sea surface temperature with longitude. Warmer water projects poleward along the western boundaries of the ocean. The eastern tropical regions of each ocean are cooler than the western tropical margin. These are due to the movement of seawater in the horizontal (ocean currents) and vertical (upwelling/sinking) directions. Temperature and density of ocean water are related inversely: warm water means low density, cold water means denser seawater. The salt content of the water also affects Ocean density.

3. Sea Surface Salinity: Sea water is about a 3 3. Sea Surface Salinity: Sea water is about a 3.49% salt solution, the rest is freshwater. The more saline, the denser the seawater. As the range of salt concentration in the ocean varies from about 3.2 to 3.8%, oceanographers refer to salt content as 'salinity', express salt concentration as parts per thousand; 34.9 ppt is the average salinity. As seawater evaporates the salt remains behind, only the freshwater is transferred from the ocean to the atmosphere. A region of excess evaporation, such as the subtropics tends to become salty, while the areas of excess rainfall become fresher. Sea ice formation also removes freshwater from the ocean, leaving behind a more saline solution. Along the shores of Antarctica this process produces dense water. Salinity reflects the workings of the hydrological cycle: the movement of freshwater through the earth/ocean/atmosphere system. 4. Below the Sea Surface: Waters warmer than 10°C dominate the sea surface but do not extend much below 500 m within the ocean; tropical and subtropical surface water provide is just a veneer of warmth over a cold ocean; typical deep ocean temperature vary from –1° to 3°C. The sharp drop off in temperature with depth is called the thermocline. The warm surface water is generally saltier than the cooler deep or polar waters. The halocline marks the drop of salinity with depth that accompanies the thermocline. The surface water warmth overrides the saltiness in governing density, so that the warm surface water regions coincide with buoyant (less dense) water. In polar regions buoyancy of the surface layer is mainly a consequence of the freshness of the surface water. Deep cold waters derive their properties at the sea surface during winter at high latitude.

5. Deep Water Masses: The deep Atlantic is relatively salty (34. 9) 5. Deep Water Masses: The deep Atlantic is relatively salty (34.9). This water is derived from the sinking of chilled saline surface water in the northern North Atlantic. The cooling makes the surface water dense, forcing it to sink, or convect into the deep ocean, and spread southward at depth. It is called North Atlantic Deep Water (NADW). In contrast the deep Pacific is lower in salinity (34.7), as it experiences no deep convection of cooled salty surface water, its surface layer is too fresh and buoyant to sink. Pacific deep water is derived from the lower salinity water column of the southern ocean. Towards the sea floor, temperatures are near 0°C marking the presence of Antarctic Bottom Water (AABW) derived from the very cold (-1.9°C; 34.65)), dense water along the shores of Antarctica. At the base of the thermocline is the low salinity Antarctic Intermediate Water (AAIW) derived from sinking of cool (3° to 4°C), low salinity waters (34.4) from 50°- 60°S marking the Antarctic Circumpolar Current and ocean polar front zone.