열수분출구를 찾아서: 2005년 DSHEEP 비스마크해 크루즈에선 무슨 관측이 수행되었는가?

Abstract

Hydrographic survey and bottom-current measurements were carried out in the Western Spreading Ridge of the Bismarck Sea. For the sake of capturing the plume(s) from hydrothermal vents, vertical profiles of temperature-salinity-turbidity with water samples were collected by CTD castings at 36 stations around the submarine volcanic bodies. Three current-meters were moored for about 5 days (from October 29 to November 2, 2005) and recovered in order to figure out the background current structure at the passage (2o56.147'S, 147o14.963'E) near the caldera (Mata Na Kul). The prominent feature of the submarine volcano is that the turbidity strikingly increases near the bottom due to the resuspension by the hydrothermal plume. The other hydrographic features are not much different in general; the surface temperature is about 30oC and the mixed layer depth with the dissolved-oxygen contents of 2.5~3.0 ml/l is formed down to 50 meters, salinity-maximum layer (35.6~35.8 psu) exists between 100 and 200 meters. Below the surface mixed layer, dissolved oxygen contents sharply decrease down to about 2ml/l. Turbidity is vertically almost constant with a slight maximum near the salinity-maximum layer at the most of the CTD stations, except inside the bottom of the known caldera crater and around the newly-found two submarine volcanic bodies named as 'Big Coma' and 'Little Coma' by our survey team. The average speed of the bottom currents were about 4cm⋅s-1 at 130 meters above bottom (=mab) (or 1120m) and about 2cm⋅s-1 at 80mab (or 1170m) and 30mab (or 1220m) with the maxima of 7~10cm⋅s-1. The energy spectrums show that there are peaks at the periods of 11~14 hours and of 6~9 hours at the three depths, but there is another peak at the period of about 22 hours at the middle depth (or 80mab). The progressive vector diagram shows that the resultant direction of the flows are northwestward at 130mab and 80mab while it is southwestward at 30mab. It was f