Seasonal deep mixing in the North Atlantic is a key process in the Atlantic Meridional Overturning Circulation as surface waters are mixed into the deep ocean carrying with them heat, nutrients, dissolved gases, and organic matter. This circulation is a key component of the earth’s climate system and the global carbon cycle. This data nugget highlights the seasonal mixing cycle of water around the OOI Global Irminger Sea Array, a location of deep water formation, as exhibited through its temperature and salinity at three depths within the water column (surface, mid, and deep waters).
During the winter months, heat radiates from the warm southern water that flows into the Irminger Sea into the atmosphere. Additionally, strong winds and storms mix the water column, as evidenced in these data by similar the temperature and salinity observed throughout the water column in winter months. Then, during the summer months, the winds calm and the water column stratifies. Stratification is caused by two processes, first, the surface layers are warmed by the sun leading to temperatures close to 10oC while bottom layers remain cold; second, surface salinity decrease as winter ice melts.
By capturing these annual cycles across decades, scientists can observe variation between years, discover drivers of that variation, and distill long term trends in annual mixing patterns.