Cruise Report, RV ATAIR, Cruise 0671021-1, Bremerhaven - Thyboron - Aberdeen, 18 Jul —- 10 Aug 2023 
The particular cruise 067/021-1 of summer 2023 consisted of two legs, with leg 1 covering the 
southern to central part of the North Sea and leg 2 covering the central to northern part of the 
North Sea. Leg 1 with departure in Bremerhaven, Germany, on 18 July led to the port of Thy- 
borgn, Denmark, where the vessel arrived on 30 July (compare Figure 1.1). The port stay 
during 30 July and 1 August was used to exchange crew members and scientific participants 
(see Section 2). The cruise was resumed on 1 August, when the vessel departed from Thy- 
borgn in order to pursue leg 2 of cruise 067/021-1 in the northern part of the North Sea, which 
ended with the vessel arriving in Aberdeen, UK, on 10 August 2023. 
Different from previous cruises, in summer 2023, the spatial resolution of the northern sections 
af cruise 067/021-1 was increased in order to resolve smaller scale oceanic structures. Fur- 
thermore, two survey lines located to the west and east of the Orkney and Shetland Islands 
sovering the inflow of Atlantic Water into the North Sea were planned. 
The major purpose of cruise 067/021-1 based on respective measurement is to assess the 
state of the North Sea in summer 2023 with focus on the physical state. Respective large-scale 
data will contribute to investigating the hydrographic state of the water column in different re- 
gions of the North Sea. Furthermore, temporal hydrographic changes as they become obvious 
when bringing the data into context with data from previous cruises shall be addressed. 
Particular objectives related to cruise 067/021-1 addressing the state of the North Sea in 2023 
are the following: 
How far does the Atlantic Water (AW) that enters the North Sea at its 
oropagate southward in summer 2023? 
Nhere does the main inflow take place? 
How far does AW entering the southern North Sea via the English Channel penetrate 
northwards in summer 2023? 
What is the respective regional sharpness and depth of the thermocline? 
Nhat is the total salt and heat content of the North Sea in summer 2023? 
Where is the Baltic outflow located? 
Overarching objectives that address temporal changes on different time scales are 
How do changes in the Northeast Atlantic happening on time scales ranging from 
seasonal to decadal affect the North Sea? 
Which processes are linked to the variability in the North Atlantic Oscillation (NAO) and 
to what extent? 
Chlorophyll-a and phytoplankton sampling carried during the cruise will serve for improving 
remote-sensing products and satellite sensor validation by means of comparison with in situ 
data.