HEAT BUDGET OF A WATER COLUMN, AUTUMN, NORTH ATLANTIC OCEAN

Abstract

The recent availability of extensive ocean and weather data makes it possible to re-examine the heat budget of an ocean water-column over a short time interval, taking into account more completely than before the effects of all physical processes which can be computed. The results of such a study are reported. Such a column, fixed in space, includes a changeable water mass extending from the ocean surface to a level of no thermal change with time. The effects of solar and back radiation, evaporation, and the curl of the wind stress probably are important in determining trends of heat-energy change in such an ocean column. The change due to these factors was obtained from data taken by North Atlantic weather ship ?C? (52°45'N, 35°30'W) during the autumn season of 1948 and from U. S. Weather Bureau five-day mean surface maps. The residual change, remaining after the above listed effects have been taken into account, varies in a manner suggesting it may include effects of horizontal advection as a large portion. The residual also includes all the measurement errors, effects of smoothing data, and inaccuracies of estimating methods. The amount of thermal change in the ocean column may be represented by the area between successive bathythermograph (BT) traces plotted upon identical coordinates. When this area is compared with that resulting from translating the BT traces along the temperature axis to a best-fit position, the difference between the two areas represents the thermal change which is uniform throughout the column depth. Such a thermal change could arise from horizontal advection which is constant throughout the vertical extent of the column. The area remaining between the superposed BT traces tends to vary in agreement with the summed thermal change contributed by the four factors listed above. The heat gain of the ocean column for the 1948 autumn almost equalled the heat loss. This suggests again that advection of warmer water into the column has compensated for the heat losses due to decreasing solar and back radiation and increasing evaporation as the season progressed. No such balance was attained on a weekly basis.