The search for MH370 and ocean surface drift – Part IV
This short report re-examines the question of how effective the March-April surface search was for ‘ruling out’ segments of the 7th arc as being the location of MH370.
One might think that even if the debris field was within a particular day’s search box that the probability of detecting the debris could be small because the spacing between the search tracks was necessarily large (in order to cover the vast distances searched) compared to the detection range. This would certainly be correct if either 1) the number of debris items was small, or 2) the debris items were all close to each other.
We now know (from the number of items that have been found washed ashore) that the number of floating debris items was not small. But while we cannot prove that these were not all close to each other and therefore potentially overlooked, the chance of this happening is very low. Winds, waves and ocean turbulence disperse objects, potentially over large distances after a week at sea. The rate of spreading of the debris field increases as time passes, as stretching and shearing by ever-larger ocean eddies takes place.
In this report we show that the debris field resulting from an example crash site at 30.5°S on the 7th arc was 1) largely within the bounds of the area searched during 5 days, and 2) probably spread out across a distance spanning several of the search tracks. Consequently, there were many opportunities for debris to be detected, suggesting that the probability of all debris items being overlooked is small.
Our re-assessment of the surface search benefits from 1) the evidence that an extensive debris field was indeed there to be found, and 2) refined estimates of the surface currents, allowing us to re-assess how well the search boxes overlapped with the potential locations of the debris fields.