Recently graduated: end of an amazing adventure and beginning of another

by Tillys Petit

My last contribution on this blog reminded the importance of in-situ data measurements on the evaluation of numerical modeling used to predict climate. As part of my PhD thesis, I had the chance to record, process and analyze observations across and along the Reykjanes Ridge within the framework of the RREX project. It included an experience at sea during the RREX cruise in 2017, which was an amazing human and scientific experience. Now that my PhD ended, I would like to tell you about the scientific results that were obtained. 

During my PhD, I studied the connection between the Iceland Basin and the Irminger Sea through the Reykjanes Ridge. A main result was to describe and quantify the top-to-bottom transport of the subpolar gyre that crossed the Reykjanes Ridge during the summer 2015. These results highlighted interconnection between the two main along-ridge currents: the southwestward East Reykjanes Ridge Current (ERRC) in the Iceland Basin and the northeastward Irminger Current (IC) in the Irminger Sea. From about 56 to 63°N, the hydrological properties, structures and transports of the ERRC and IC consistently evolved as they flowed along the Reykjanes Ridge. During my PhD, I showed that these latitudinal evolutions were due to flows connecting the ERRC and IC at specific locations through the complex bathymetry of the ridge, but also to significant connections between these currents and the interiors of the basins. These results highlighted a more complex circulation in the vicinity of the Reykjanes Ridge than it was assumed.

From three different cruises and Argo floats, I also investigated the deep circulation and properties of overflow water through the deepest sills of the Bight Fracture Zone. At the end of my PhD, I showed the strong variability of its transport and property over time by comparing three successive years. Now, I think that it could be interesting to continue this study and to better understand the variability of overflow water at higher frequency. As a continuity of my PhD, I am thus exciting to investigate the variability and linkage between the overflow water transports and properties across the Iceland-Scotland Ridge and the Denmark Strait as part of my postdoctoral position. These inflows from the Nordic Seas feed the lower limb of the Meridional Overturning Circulation and are crucial to characterize the variability of the North-Atlantic subpolar gyre. I am excited to fulfil this study by using the OSNAP array that provides new and key measurements of the AMOC, and also to move in USA for a new beautiful and rewarding postdoctoral experience.

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