Combination of oceanographic data with wind data acquired during the cruise to try to draw conclusions on wind stress, Ekman transport and Ekman layer for selected zones in the area of operations LT Guillermo Coll

Outline Motivation Theoretical background Observations Results/Conclusions

Motivation Try to see if theoretical processes can be observed in practice Ekman layer, Ekman spiral, Ekman transport were studied in OC3240 (Ocean Dynamics I) Steady wind conditions in certain areas of the cruise seem adequate

Theoretical Background wind u Momentum is imparted to the water by the wind stress and transported down by the vertical friction

Theoretical Background There are two distinct components of the flow: Geostrophic component Ekman component caused by friction caused by the pressure gradient

Theoretical Background Ekman equations The amplitude of Ekman velocity exponentially decreases with depth Direction of Ekman velocity rotates clockwise with depth

Theoretical Background Ekman layer = Frictional influence layer. Depth at which the current forms 180 degrees with respect to the wind stress

Observations

Observations WIND LEG-I

Observations WIND LEG-I

Observations

Observations

Observations

Observations WIND LEG-II

Observations

Observations 08/01 1800 UTC to 08/03 0700 UTC

Observations Current data obtained from R/V Point Sur ADCP. u,v components measured at mean depth of 8m bins, starting from z=-15 m. Data used from 6 upper bins. (z=-19 m to z= -67 m). Data downloaded every 5 min.

Results In general, computed directions in the upper layer don’t show clear relation with wind stress direction.

Results SHIP MOVING

Results SHIP MOVING Large standard deviations of u and v when the ship is moving

Results SHIP MOVING

Direction Correlation Coefficient Matrix (08/02 0253-0755 UTC) Results SHIP MOVING Direction Correlation Coefficient Matrix (08/02 0253-0755 UTC) Depth 19 27 35 43 51 59 67 19 1.0000 0.9314 0.9127 0.8890 0.7442 0.6318 0.7135 27 0.9314 1.0000 0.9633 0.8767 0.7456 0.6064 0.5713 35 0.9127 0.9633 1.0000 0.9433 0.8303 0.7227 0.6672 43 0.8890 0.8767 0.9433 1.0000 0.9533 0.8593 0.8277 51 0.7442 0.7456 0.8303 0.9533 1.0000 0.9394 0.8489 59 0.6318 0.6064 0.7227 0.8593 0.9394 1.0000 0.9094 67 0.7135 0.5713 0.6672 0.8277 0.8489 0.9094 1.0000

Speed Correlation Coefficient Matrix (08/02 0253-0755 UTC) Results SHIP MOVING Speed Correlation Coefficient Matrix (08/02 0253-0755 UTC) Depth 19 27 35 43 51 59 67 19 1.0000 0.5484 -0.6668 -0.8466 -0.8687 -0.7890 -0.3240 27 0.5484 1.0000 0.0761 -0.2385 -0.2987 -0.2947 -0.1203 35 -0.6668 0.0761 1.0000 0.8891 0.6820 0.4988 0.1398 43 -0.8466 -0.2385 0.8891 1.0000 0.9044 0.7422 0.2163 51 -0.8687 -0.2987 0.6820 0.9044 1.0000 0.9355 0.3470 59 -0.7890 -0.2947 0.4988 0.7422 0.9355 1.0000 0.5826 67 -0.3240 -0.1203 0.1398 0.2163 0.3470 0.5826 1.0000

Results SHIP AT STATION

Results SHIP AT STATION Large standard deviations of u and v when the ship is at station

Results SHIP AT STATION

Direction Correlation Coefficient Matrix (08/03 0259- 0545 UTC) Results SHIP AT STATION Direction Correlation Coefficient Matrix (08/03 0259- 0545 UTC) Depth 19 27 35 43 51 59 67 19 1.0000 0.8154 0.7865 0.6834 0.5378 0.3299 0.1661 27 0.8154 1.0000 0.8565 0.6156 0.3475 0.0508 -0.1409 35 0.7865 0.8565 1.0000 0.8874 0.6226 0.4006 0.2419 43 0.6834 0.6156 0.8874 1.0000 0.8806 0.7185 0.5645 51 0.5378 0.3475 0.6226 0.8806 1.0000 0.9238 0.7961 59 0.3299 0.0508 0.4006 0.7185 0.9238 1.0000 0.9555 67 0.1661 -0.1409 0.2419 0.5645 0.7961 0.9555 1.0000

Speed Correlation Coefficient Matrix (08/03 0259- 0545 UTC) Results SHIP AT STATION Speed Correlation Coefficient Matrix (08/03 0259- 0545 UTC) Depth 19 27 35 43 51 59 67 19 1.0000 0.9497 -0.4749 -0.5511 -0.5486 -0.4905 0.3549 27 0.9497 1.0000 -0.3842 -0.5341 -0.5309 -0.5035 0.2707 35 -0.4749 -0.3842 1.0000 0.9251 0.8386 0.6907 -0.1491 43 -0.5511 -0.5341 0.9251 1.0000 0.9599 0.8516 -0.0941 51 -0.5486 -0.5309 0.8386 0.9599 1.0000 0.9396 -0.0881 59 -0.4905 -0.5035 0.6907 0.8516 0.9396 1.0000 0.1572 67 0.3549 0.2707 -0.1491 -0.0941 -0.0881 0.1572 1.0000

Conclusions

Conclusions No clear results where obtained about the relation between wind stress and currents in the upper layers.

Conclusions No clear results where obtained about the relation between wind stress and currents in the upper layers. A long time series is needed to average out current forcing due to tidal currents, internal waves, etc..

Conclusions No clear results where obtained about the relation between wind stress and currents in the upper layers. A long time series is needed to average out current forcing due to tidal currents, internal waves, etc.. Locally, some clockwise current shear was observed and there was good correlation between the current direction change in the upper layers.

Conclusions No clear results where obtained about the relation between wind stress and currents in the upper layers. A long time series is needed to average out current forcing due to tidal currents, internal waves, etc.. Locally, some clockwise current shear was observed and there was good correlation between the current direction change in the upper layers. On a moving ship, ADCP current data might not be accurate enough for this research.

Conclusions No clear results where obtained about the relation between wind stress and currents in the upper layers. A long time series is needed to average out current forcing due to tidal currents, internal waves, etc.. Locally, some clockwise current shear was observed and there was good correlation between the current direction change in the upper layers. On a moving ship, ADCP current data might not be accurate enough for this research. Geostrophic data are needed to complete the study.

QUESTIONS?