Irene has now made its way north of the Mid-Atlantic Bight leaving her mark inshore and along the coast. RU16 fought the onshore currents associated with the northern edge of the storm until this morning when the currents switched as the eye passed overhead. The last several surfacing show that the glider is now making much better progress offshore. The glider is now offshore of the large phytoplankton bloom we were monitoring before Irene’s arrival. You can follow that event here: (http://maracoos.org/summerbloom/). The map below shows the bloom location several days before the storm as the color background underneath RU16’s path.
Preliminary data from the glider shows that the impact of Irene was felt deep into the water column. Before the storm, the ocean had a very warm surface layer above a very cold bottom layer. The temperature gradient between the two is one of the largest in our global ocean. You can see the pre-storm conditions in the plot below. Look at the data collected between August 26 and August 28.
Irene’s influence is see near the left edge of the plot with a rapid cooling of the surface layer from 25 degrees C before the storm to 19 degrees C after the storm. That is over 11 degrees F! In addition the surface layer deepened significantly from 15 meters to almost 30 meters. Irene has doubled the thickness of the mixed layer.
The mixing and deepening of the surface mixed layer is also seen in the dissolved oxygen data. Relative to before the storm the mixed layer is now slightly lower dissolved oxygen concentrations in the near surface but has now delivered more oxygen rich water deep in the water column. As with Ernesto 5 years ago, Irene did not mix away the strong stratification in the deeper waters of the mid-shelf. RU16 will now turn back inshore to see how Irene’s influence was felt in the shallower waters coincident with the highest cell concentrations associated with the pre-storm bloom.