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What You Can’t See

R/V Neil Armstrong passed this iceberg as the ship approached one of the OSNAP (Overturning in the Sub-polar North Atlantic Program) mooring sites east of Greenland last week. Deep-keeled ice poses a threat to OSNAP’s sub-surface moorings and the instruments they hold; instruments near the surface are connected with weak links so they can snap off if struck. Last year, an OSNAP mooring was hit by an iceberg, dislodging an instrument that eventually washed up in Greenland, 350 miles away. It was discovered by a fisherman, who gave it to the Greenland Fisheries Institute, which sent it back to WHOI. The instrument’s data survived—and showed it was lodged in the iceberg for more than two and half months before melting out and rising to the surface. (Mattias Cape, Woods Hole Oceanographic Institution)