We all agree that observation has always been essential to scientific discoveries. Before the age of satellites, atmospheric observatories, ocean observatories and efficient computers, most scientific discoveries were observational-based. This one is the story of Norwegian scientist-cum-explorer Fridtjof Nansen, who was also famous for his humanitarian services and was awarded the Nobel Peace Prize in 1922 for his service in tackling the refugee crisis during World War-I.
As an explorer, Fridtjof Nansen started exploring the Arctic Ocean and Greenland. However, the expedition to the North pole was about to change his life and become memorable. Tracked back to 1893, the Fram Expedition failed to achieve its objective led by the Norwegian explorer Fridtjof Nansen from 1893-1896. He proposed and aimed to reach the geographical North Pole using the naturally driven arctic westward current through the Arctic ocean. However, he was trapped in the Arctic Ocean for three long years and continuously drifted by the ocean currents. He was believed to be intentionally trapped in the sea ice for the experiment. Although he failed to achieve his objective of reaching the North Pole, he made a lot of observations on the ship itself. He observed that the floating ice sheets were not moving in the same direction as the wind blowing; instead, they were mainly drifting towards the right-hand side of the wind direction.
Then, a student of Nansen named Vagn Walfrid Ekman started to analyse these observations. He investigated the prevailing wind forcing the surface water to move; however, due to the earth’s rotation (Coriolis effect), the water (ice sheets) instead moved at an angle right in the northern hemisphere and left in the southern hemisphere. The direction and speed further change with increasing depth.
Interestingly, the surface water moves at an angle to the direction of the wind, and then the water underneath turns a bit more concerning the surface water; and the water below that even turns more. The entire process makes a spiral shape water movement between 100 to 150 meters deep, called an Ekman spiral (Published in 1905)l. Ideally, the wind blowing across the ocean surface would move the surface water at an angle 45 degrees off the right wind direction in NH and vice versa in the SH. The average direction of all this turning water is about a right angle from the wind direction (in the northern hemisphere); this average is Ekman transport. Earth's ocean circulations have been rapidly changing, and they are the medium of transportation for marine nutrients. Therefore, Ekman transport is essential in understanding the biogeochemical processes and their variations in the world’s oceans at various time-scale.
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