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The oceans play a major role in the science of global warming and in Nebraska’s climate and weather.

The main source of precipitation in Nebraska is from the Gulf of Mexico. As gulf air masses, rich with moisture, flow inland, they are more apt to reach eastern Nebraska, so eastern Nebraska is wetter on average. More details can be found in “Understanding and Assessing Climate Change-Implications for Nebraskans”, a report prepared by University of Nebraska-Lincoln faculty.

To understand ocean science, one must first examine the properties of the water molecule, which resembles two small-spheres of positively-charged hydrogen atoms attached to a large-sphere oxygen atom that is negatively-charged. It is a dipolar molecule (negative and positive poles) that can form multiple compact clusters with other water molecules.

At the boiling point, all these bonds are broken, and water becomes a gas. At the freezing point, a crystal mineral (ice) forms that is less dense than water (liquid). Molecular motion increases as water warms, so size of clusters decreases and the water becomes less viscous and less dense. Water has the highest specific heat capacity of any substance because considerable heat energy is required to break down the size of clusters.

At the ocean's surface, water molecules break free (evaporate) and are moved into the atmosphere. Warmer water means greater evaporation rates. Most of the Earth’s surface (71%) is covered by oceans, so the properties of water play an important role in global warming effects.

Most heat, generated by global warming processes, is currently being absorbed by the oceans. Because of water's high heat capacity, there is currently small ocean-temperature increases, but the large surface area of the oceans means there is increasing evaporation to the atmosphere.

The equatorial oceans (sun is more directly overhead) absorb much of the sunlight resulting in warming of the surface water, which becomes less dense. The warmed surface water flows to areas of less heating.

The Gulf Stream represents the flowing of less-dense warm water toward Greenland, where it gives up its heat to the atmosphere. The cold water, now denser, sinks into the oceans depths on a path back to the tropics, keeping the Titanic very cold as it passes.

The overall cycle moves heat from the tropics to the high latitudes, where this heat is transferred to prevailing winds, which keep Europe warmer than it would be without the added heat and also melting glaciers in high latitudes. If the ocean water gets too warm and increased melting glacier water (much less dense than seawater) mixes in, the current can be slowed or stopped because the smaller density differences can no longer sustain this cycle.

There is strong evidence that this current is now slowing down. Europe, ironically, could become much cooler because of the disruption of this current by global warming.

Glaciers in Greenland and the Antarctic represent freshwater, which, if melted, could raise sea level by hundreds of feet. Because most people on Earth live close to an ocean, the impact of sea-level rise is huge.

Ocean water is now flowing below the floating ice sheets in the Antarctic melting the ice at a very rapid rate. A rise of sea level will enhance this process. More open water instead of ice in the Arctic Ocean means more absorption of sunlight and further heating of Arctic ocean water and ice melting.

This is a runaway process, as evidenced by the increasing areas of open water each summer. It is likely that the Arctic Ocean will be nearly ice free in future summers, according to UNL researchers. All of this open water means more evaporation to the atmosphere and changing of climate patterns.

Increased moisture in the atmosphere means more available energy for more and stronger storms like hurricanes, thunderstorms and hail across the globe. Nebraska will be affected.

The true Earth model tells the story. To date, most of the increase in carbon-dioxide emissions because of humans is being absorbed by the oceans. Without this process, CO2 concentrations in the atmosphere would be way past critical points. But, as oceans warm, they are less able to absorb CO2 from the atmosphere, so more generated CO2 stays in the atmosphere accelerating global warming. High latitudes are warming even faster.

Measurable sea-level rise is occurring because of melting of glaciers and expansion of ocean water with warming. The data from the true Earth model shows the impact in oceans of global warming.

This is science, not a belief -- and it has consequences for Nebraska.

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Darryll Pederson is an emeritus professor of hydrogeology in the Earth and Atmospheric Sciences Department at the University of Nebraska-Lincoln.

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