An interesting phenomenon with glaciers is that some are so enormous that they actually draw water towards them, creating tides of their own. By attracting water they are artificially raising the sea level around them. However, once they start melting, they lose this power of attraction and the sea level drops around them and it’s not made up for with the water melt from the glacier. This effect radiates out to about a thousand miles from the glacier.
So does this mean the sea is not really level?
“Level” is an averaging concept we calculate. The seas themselves are affected by all sorts of things, from the glaciers of course, to being thrown about by tidal forces, to covering countless gravitational anomalies, to even the very basic issue of being on a spinning oblate spheroid rather than a perfect ball.
Depending on how detailed an area or time frame you’re looking at, you could probably add “constructive and destructive deep wave patterns” (but we probably shouldn’t go there). It would also be reasonable to factor in seasonal thermal expansion effects, and in fact I’d be surprised if that wasn’t already done.what is reason of glaciour made up and melt-