What losing access to the sea would do to a modern economy

How damaging would it be if a modern society were completely denied access to the sea?

Economically catastrophic; maritime trade would disappear, and countries such as Britain would face acute food-supply problems even with nearby Irish imports.

Arpeggio of Blue Steel supplies the fictional premise: humanity loses access to the seas and most satellite services. The economic reasoning concentrates on the loss of maritime transport and international trade. British food supply provides a concrete example of the dependence created by overseas imports. Ireland is emphasized as a nearby supplier, connecting the argument to the strategic importance of the Irish Sea. Proximity changes the geography of the problem, although the stated scenario still denies transit across that water.