372 Alf Trolle. 



The warm and salt bottom-water in Øresund was drawn out 

 and replaced by less saline and colder water from the upper layers 

 in the sea. 



In the latter part of the winter — after January 1907 — the 

 inflow of chlorides and heat from below gradually decreased; the 

 water in the deeper layers, which now came up on the barrier, 

 had a similar temperature and salinity as the water there. A layer 

 with uniform salinity was formed, the cold spreading downwards 

 through it by convection currents. 



In the middle of May this layer had a thickness of 140 m.; the 

 salinity throughout was 32.48 p. m. and the temperature — 1.78° 

 (the freezing point temperature corresponding to this sahnity) (see 

 series XX). 



From the middle of May to the middle of June 1907 warmer and 

 salter bottom-water again made its way into Øresund, probably pressed 

 in by density changes in the sea, as no such changes occurred at 

 the same time in the upper layers in the inner waters (the ice had 

 namely a thickness of ca. l%m. everywhere in the fjords and the 

 sea ice was sohd and immovable). 



This increasing warmth and salinity were propagated quite slowly 

 from below upwards to a depth of ca. 50 m. (series XX and XXV). 



In the series XXXIV (middle of July) we see, that this so-called 

 ascending wave of heat meets with a slight warming of the upper- 

 most layers, caused by a slight mixture of warmed up water from the 

 rivers which had begun to flow in the beginning of June. (The salin- 

 ity had decreased down to ca. 10 m., and the temperature increased). 

 From 10 — 75 m. the salinity remained almost unchanged, but the 

 temperature rose a little. Thus, mixing had occurred here between 

 water-layers with salinity one above and the other below 32.48 p. m. 

 and both with temperature above freezing point. 



From the middle to the end of July the ice still lay unbroken 

 everywhere in the fjords; nor did any great salinity and tem- 

 perature changes occur here during this period. (In series XXXIX 

 the CI. p. m. are not quite reliable — they are probably ca. 0.08 

 p. m. too low, and assuming this, the temperature and salinity had 

 very slightly increased during this period). 



In the beginning of August the ice broke up in the fjords and 

 in the course of the month thereafter a great decrease in salinity and 

 increase in temperature occurred in the layer — 50 m. (series XLII). 

 This layer had a well-defined boundary towards the mixed layer in 

 50 — 75 m., where the salinity remained nearly unchanged, whilst the 

 temperature rose. In the under layer (75 — 150 m.) the temperature 

 and salinity rose a little. 



As already mentioned, the condition has been, that the upper 

 layers in under the land have decreased more in density than the cor- 



