Fig. 5: Continuous internal wave activity vertically displacing the temperature layers of the fjord.

a, A 1.5-day-long temperature profile along the sloping cable from DTS (see inset at the bottom left corner of c and depth scale on the left of a). IGWs with a 15–30 min period are predominantly visible where the vertical temperature gradient is the largest (sharp transitions between yellow–orange, orange–purple and purple–blue). b, Magnification into the marked region of a. c, Unfiltered DAS raw phase record of the same cable section as in a. For the IGW frequencies shown (<10 mHz), the measured phase is proportional to the strain rate along the cable, caused by temperature change. d, Magnification into the marked region of c, showing the vertical displacement of the sharp temperature steps by changes in strain rate propagating up and down. Positive (red) values indicate an increase in temperature and negative (blue) values a decrease. m.b.s.l., metres below sea level.