Then he'd eye cross sections of shells, looking for patterns, matching growth rings, finding overlaps, all with the goal of eventually lining up enough shells to build a master chronology of growth increments covering a millennium.
[Source] It lives entirely in fertile Arctic and sub-Arctic waters, unlike other whales that migrate to feed or reproduce to low latitude waters.
Just like tree rings say a lot about growing seasons over time, annual growth increments in the shells can tell researchers a lot about ocean conditions over time.
Wanamaker, now an Iowa State University associate professor of geological and atmospheric sciences, started building the marine archive by processing all those clams - painstaking lab work that involved sectioning shells, embedding shell slices in epoxy blocks, measuring down to a millionth of a meter, drilling samples, radiocarbon dating and determining oxygen isotopes.
Later, the Icelandic researchers on the cruise which discovered the clam named it Hafrún (a woman's name which translates roughly as "the mystery of the ocean"; taken from haf, "ocean", and rún, "mystery").
Ming/Hafrún was dredged off the northern coast of Iceland in 2006.