On the basis of the CTD stations, five transects cutting across the main bathymetrical and hydrographical structures of the study area were defined (Fig. 1) and interpolated for salinity, temperature, and fluorescence, respectively (Fig. 2). Transects 1-4 cut across the entire study area, starting in CSW, moving through DB, and ending in GSW. Transect 5 is located mainly in GSW, with only one station in DB (Fig. 1). All transects were characterized by relatively warm water (2.2 °C) in the upper water column (0-50 m) (Fig. 2a, d, g, j, m). In CSW, the intermediate water body (50-250 m) consisted of relatively cold water (-1.4 °C), which stretched out eastwards into the upper part of the intermediate water body in DB. In GSW, the intermediate water body was relatively warm (2.3 °C). The deeper part of the water body (250–500 m) was relatively warm in all three areas (2.1 °C) with a gradual increase in temperature from CSW toward GSW. On all transects, the salinity ranged from 30.5 to 34.5, increasing with depth. The salinity was in general lowest in the surface waters (0–50 m) of the CSW and highest at depth (300–500 m) in the GSW (Fig. 2b, e, h, k, n), the latter as a result of the inflow of warm Atlantic water. At any particular depth, salinity always increased toward east. Fluorescent material was only found in the upper 50 m of the water column with slightly higher values in CSW and GSW(0.9) than inDB(0.6) (Fig. 2c, f, i, l, o). St. 1 located on the shallow St. Hellefiskebanke (GSW), which is renowned for its primary production, had the highest fluorescence levels recorded in the study area. However, if st. 1 is excluded, there were significantly higher levels of fluorescent material in CSW than in GSW (p[0.0001, t test).|Between September 7 and September 22, 2009, a total of

45 stations were sampled from the research vessel R/V

Bjarni Sæmundsson (Marine Research Institute, Reykjavik,

Iceland). Sampling was carried out during full 24-h cycles,

every 4–6 h. The survey was initiated at Sisimiut

(Southwest Greenland) and covered a route of 1,485 nautical

miles (nmi). The order of the station numbers corresponds to the chronological sequence of the survey.

The survey route transects the main bathymetric and

hydrographical features described above. For the ease of

presentation, the study area was subdivided into three

areas: Canadian Shelf Waters (CSWs), DB, and Greenland

Shelf Waters (GSWs). Stations shallower than 700 m are

assigned to CSW on the Canadian side and to GSW on the

Greenland side, whereas stations deeper than 700 m are

defined as DB. One exception to this rule is

station st. 37, which is assigned to DB even though it is

shallower than 700 m. This was done because it is located

in the central part of the study area far off the regular

shelves and surrounded by much deeper water. It presumably

represents a very localized peak in DB, which has not

before been captured in bathymetry data collections

(Jakobsson et al. 2012). At all 45 stations, vertical profiles of temperature, salinity and fluorescence were obtained from the surface down to

500 m using a SBE 9 plus CTD (SeaBird Electronics)

equipped with a Seapoint chlorophyll fluorometer (Seapoint

Sensors Inc). Due to an unfortunate loss of samples, the

fluorescence readings could not be calibrated to the study

area and are therefore only used as a proxy for the relative

differences in Chlorophyll-a concentration between stations.