Observations of abyssal flow and mixing

Scientists once thought the abyssal ocean, near the ocean bottom, was nearly stagnant, but recent observations show it is quite dynamic and that abyssal mix- ing plays an important role in the general circulation.

Contributing to understanding of abys- sal flow, Alford et al. report measurements of temperature and velocity in the abys- sal ocean from two moorings near Hawaii. They found three major cold events in their 2.5-year record, indicating that mix- ing events are strongly intermittent. They focus in detail on one unusual cold event that appeared in two pulses spaced about 2 weeks apart in September and October 2010. The event included an anomalously low temperature about 0.15°C below nor- mal temperatures that extended more than 500 meters above the ocean bottom as well as vigorous turbulent flows. (Geophysical Research Letters, doi:10.1029/2011GL048075, 2011) —EB