It has frequently been noted that sea-floor multiple reflection seems to be a problem largely in the polar latitudes only--rarely in equatorial regions. This observation might be dismissed as being based on the statistics of small numbers, but two reasons can be given why the observation may be true. Each of these is of interest whether or not the statistics are adequate.
It happens that natural gas is soluble in water and raises the temperature of freezing, particularly at high pressure. Ice formed when natural gas is present is called gas hydrate. Thus there can be, under the liquid ocean, trapped in the sediments, solid gas hydrate. The gas hydrate stiffens the sediment and enhances multiple reflections.
A second reason for high multiple reflections at polar latitudes has to do with glacial erosion. Ordinarily ocean bottoms are places of slow deposition of fine-grained material. Such freshly deposited rocks are soft and generate weak multiple reflections. But in polar latitudes the scouring action of glaciers removes sediment. Where erosion is taking place the freshly exposed rock is stronger and stiffer than newly forming sediments. Thus, stronger sea-floor reflections.
Continents erode and deposit at all latitudes. However, one might speculate that on balance, continental shelves are created by deposition in low and middle latitudes, and then drift to high latitudes where they erode. While highly speculative, this theory does provide an explanation for the association of multiple reflections with polar latitudes.