We know that global sea level was lower during the Last Glacial Maximum (last ice age) because loads of water was ‘locked-up’ in the ice sheets that covered northern North America and Scandinavia. Despite global sea level being lower, Maine’s relative or local sea level was HIGHER! There are massive deltas that are now used for blueberry farming. The surface of these deltas was once at the same elevation as the ice age sea level, but is now ~100 m ABOVE the present-day shoreline.
How could global sea level be lower but Maine’s sea level be higher?
Answer: The Laurentide Ice Sheet (that covered northern North America) was so massive and heavy that it DEPRESSED the land! The ice sheet weighed the land down below the low ice-age sea level!