G6 – The Little Ice Age 900-1000L-04

Connections to the Hydrosphere

Was the cause of the Little Ice Age the preceding Medieval Warming Period? If so, how would a period of warmer temperatures cause Earth’s temperature to begin to cool? This warming period may have caused the melting of the Greenland Glacier. This melting, in theory, may have caused an increase in the amount of fresh water entering the North Atlantic Ocean. This infusion of fresh water could have altered the thermohaline circulation.

The thermohaline circulation acts like an ocean conveyor belt. It carries warm water from near the equator towards the poles. This movement of water regulates global ocean temperatures. Surface temperatures and changes in the amount of freshwater entering the ocean system create density differences. The amount of salt in the water affects its density. The temperature of water also affects its density. These factors, along with wind-driven surface currents distribute heat around the globe.

One such example of the ocean conveyor belt’s effect on climate is the Gulf Stream. This current moves warm water from the equator toward the Northern Atlantic. As the water travels northward, it starts to cool. Once it reaches the north, the decrease in temperature causes it to start sinking. This region of sinking water is called the North Atlantic Deep Water.

The warm water carried north and west by the Gulf Stream has a major impact on the weather and climate conditions on the European continent. Its impacts include preventing the weather from getting too cold.

Could the thermohaline circulation have been responsible for the Little Ice Age? Consider Europe as an example. Depending on the severity, this warming period might cause polar ice caps and large continental glaciers to melt. These large melting masses of ice would flood the North Atlantic with a large amount of fresh water. This large amount of fresh water would change the density of the waters in the North Atlantic. In theory, this action would divert the Gulf Stream. As a result, the warmer waters coming from the Gulf of Mexico would not reach the British Isles and Europe. Without these currents, the area would experience cooler temperatures and an increase in rainfall. Does that mean the Medieval Warming Period was the cause of the Little Ice Age? It’s possible.