He was a student at Lund University earning a philosophy degree in 1890 and a doctorate in 1896.

In 1894, Ohlin participated in a search operation after the missing Björling–Kallstenius Expedition.

In 1898, he joined with Alfred Nathorst's expedition on the ship Antarctic to Bear Island, Svalbard and Kong Karls Land.

He participated in the Swedish Antarctic Expedition (1901–1904) led by Otto Nordenskjöld and Carl Anton Larsen.

Ohlin Island, discovered during the Swedish Antarctic Expedition, is named after him.