The role of the weather in the fate of Shackleton’s Endurance

Endurance, one of the main vessels of the Imperial Trans-Antarctic Expedition of 1914–17, became stuck and eventually was crushed by sea ice, sinking to the bottom of the Weddell Sea; yet, miraculously, every member of the expedition returned safely home. Nonetheless, it still is not clear what role the weather of 1914–15 may have played in the ship becoming beset and destroyed by the ice conditions, forcing the need for a heroic survival. Through examining the weather observations from Endurance in a climatological perspective, two key elements emerge that may have compromised the expedition. First, the austral summer of 1914–15 was marked with more extensive sea ice in the Weddell Sea both in the context of satellite observations and estimates from the twentieth century, consistent with an ongoing El Niño event. Once the ship became beset in the ice, persistent near-record minimum daily mean temperatures lasted through the remainder of the summer of 1914–15, offering little opportunity before winter to become dislodged. Second, the austral spring season of 1915 was marked by persistent high pressure anomalies in the Weddell Sea, confirmed by nearby observations and reconstructions. These extensive, persistent high pressure conditions delayed ice breakup in the Weddell Sea and moved the ship into heavier multiyear ice, ultimately limiting opportunities for an early escape from the ice. While it is impossible to conclusively prove that these exceptional conditions sealed the fate of Endurance, neighboring years do not show such extreme conditions, which may have led to a different outcome altogether.