Tides: Lifting life in the ocean

Around half of Earth's primary productivity occurs in the ocean, driven by single-celled microscopic phytoplankton who exist in an environment where the major resources for their growth have a stratified distribution. Light for photosynthesis is abundant near the sea-surface and declines rapidly with depth, while the essential nutrients for life are concentrated at depth due to phytoplankton utilization in the surface, their death, rapid sinking, and eventual break down and recycling in the oceans interior. Processes that mix deep nutrients into the upper ocean from depth regulate ocean productivity, with recent research highlighting how turbulence generated from internal tides interacting with deep topographic features (e.g., the mid-Atlantic ridge) should be added to the list of processes. Oceanic primary productivity supports marine ecosystems, global elemental cycling and the role of the ocean in regulating Earth's climate; the role of tides in these Earth System feedback mechanisms is just being recognized.