Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Maria S. Merian	MSM21-1b	09.06.2012 - 22.06.2012	NORDATLANTIK, AP 2.1 THOR VALLEY MIXING	Denmark Strait Irminger Basin

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Kanzow Torsten	Helmholtz Centre for Ocean Research Kiel (GEOMAR)	Reykjavik	Reykjavik

Ziel der Reise / Objectives of Cruise:

The R/V Maria S. Merian cruise MSm²1/1b was carried out jointly by GEOMAR Kiel and the Institut fur Meereskunde at the Centre for Marine and Atmospheric Sciences of Hamburg University. The main objectives of the cruise were to characterize the spatio-temporal variability of the Denmark Strait overflow and to identify processes responsible for the exchange of the overflow plume with ambient water downstream of Denmark Strait. A multi-platform approach was taken to achieve the goals, based on moorings, an autonomous underwater vehicle (AUV), as well as lowered and vessel-mounted observations. From these platforms, measurements of temperature, salinity, dissolved oxygen, current velocity, dissipation of turbulent kinetic energy, and bottom pressure were obtained. Altogether, twelve moorings were deployed, one mooring was recovered, data from two PIES were uploaded via acoustic telemetry, turbulence measurements on six extended AUV dives were carried out, and 92 CTD / LADCP casts were taken, 25 of which had additionally been equipped with a profiling turbulence (MSS) probe. On June 9, 2012, R/V Merian left Reykjavik. After a successful one-hour test dive of the AUV Abyss in calm seas in the bay of Reykjavik, we steamed toward Denmark Strait - our first work area. In Denmark Strait, we commenced our work in the early morning of June 10, by uploading data from a PIES via acoustic telemetry, which had been deployed approximately one year earlier. After that we carried out a CTD/LADCP section across Denmark Strait, starting from the southeast, measuring both the warm, saline Irminger current and the cold, dense Denmark Strait overflow. On the way an ADCP mooring was recovered after one year of operation. In the evening of June 11, we arrived in the second work area, located on the Greenland continental slope southwest of Denmark Strait. We stayed in this area with short interruptions until June 20. Here, the overflow plume exhibits an intense exchange with ambient Atlantic waters. In the central part of the planned mooring cluster both 3 transponders to be used as AUV navigation aids were deployed. On June 12 we deployed 4 ADCP moorings. Later that evening the AUV Abyss - equipped with a microstructure (turbulence) probe and a conventional CTD - was launched for its first extended mission in the overflow. After completion, the AUV was recovered approximately twelve hours later in the morning of June 13. To determine the stratification, parallel to the AUV mission local CTD / LADCP casts were carried out. In the following days we completed the mooring cluster, which consists of a total of twelve moorings in our approximately 20 nm by 12 nm wide work area. We carried out repeated CTD / LADCP / MSS measurements at two sites, with one located near the center of the mooring cluster, and the other south of this location, near the offshore limit of the overflow plume. In parallel, AUV missions with different configurations were carried out in the overflow plume, of which in total 5 missions were successful. In addition, near the work area, we carried out measurements along two sections from the Greenland shelf down the continental slope. Surprisingly, in the western (downstream) one, completed on June 15, water with densities in excess of 27.9 kg m-3 were found in a bottom layer extending all the way from the shelf down into the overflow plume. To establish the origin of the dense water, on June 18 we carried out CTD /LADCP measurements along a second section down the Greenland continental slope, located 35 nm east of the first one. The data from the second section did not show water with densities in excess of 27.9 kg m-3 at water depths shallower 1400 m, respectively. We left the main work area in the evening of June 20, to carry out a calibration of the EM120 swath echo sounder. We arrived in Reykjavik in the morning of June 22.

Messungen / Measurements

Verankerungen / Moorings