What is the world's northernmost lighthouse?

Svalbard is an archipelago in the Arctic Ocean roughly 800 km (500 mi) north of Norway's North Cape and a similar distance from the North Pole. Under the 1925 Svalbard Treaty the territory is part of the Kingdom of Norway but other countries have the right to exploit mineral resources (meaning coal). The only nation exercising this right is Russia, which has a mining settlement of about 600 residents at Barentsburg. The Norwegian town Longyearbyen, with a population of about 1800, is the northernmost town in the world. Both Barentsburg and Longyearbyen are on the Isfjord, which cuts across the main island from west to east. Svalbard is governed as an unincorporated territory of Norway with a governor appointed by the national government. In recent years Svalbard has become accessible by adventure cruise ships. All the lighthouses are on Spitsbergen, the largest island of the Svalbard archipelago. (Historically the entire territory was usually called Spitsbergen.)