Two gliders; Coprolite and HSB, have joined us back onboard the Discovery, having been successfully recovered today. These are Slocum Gliders, which are bright yellow, 5 feet long, 50-something kilos with a trim waist. They manipulate Archimedes’ law to steer to different depths in the water and are remotely directed by pilots operating from Southampton.
During their week-long mission, Coprolite and HSB accumulated observations of the water column, ranging from temperature and saltiness to dissolved oxygen and chlorophyll concentration. They were released in the north-eastern Labrador Sea, where they weaved in and out of a strong boundary current not far from the Greenland capital; Nuuk.
This boundary current, known as the West Greenland Current, exchanges water between both Greenland’s large continental shelf and the central Labrador Sea. This includes large-scale eddies, created by the instability of the current structure, that export water westward to the Labrador Sea’s interior. These eddies influence the formation region of a globally important deep water mass in the Labrador Sea. Recently, observations have pointed to an increased Artic freshwater presence from elevated ice melt. This trend, carried by the West Greenland Current, may restrict the extent of deep water formation.
Moreover, biologically essential nutrients, like silica, are associated with meltwater delivered from Greenland’s glacial network. Their pathways into ecosystems are controlled by circulation features dependent on the West Greenland Current, but these important circulation features often happen on small scales in space and time. It is the sampling agility of the gliders that may provide a new perspective on the circulation features initiated by this immense current.
On recovery, a hushed atmosphere swept the ship’s bridge as we squinted through a band of fog and idle seabirds for the yellow fins of the gliders. The sea surface was calm and glossy. It had the texture of jelly, with corduroy-like ripples and the gliders seemed to gloop out of it as they were whisked up into the air.
Still wet from their journey, Coprolite and HSB rest with tired batteries back on the Discovery. The mountains around Nuuk fade away into mist as the ship steams south, and it scores the surface of the Atlantic waters as it does so. We are heading towards the Southern tip of Greenland where the orange sunrise and marmalade seas will shine the toes of different mountains and, our science investigation will continue.
Jake Opher (PhD student based at the British Antarctic Survey)
The glider, Coprolite, being lowered over the side of the Discovery for its week-long survey. Photo credit: Marcus Badger
A pair of Pilot Whales basking in the early morning sun off the coast of Nuuk. Photo credit: Marcus Badger