That boundary is the ocean with its very large heat capacity. (judithcurry.com)
The oceans» large heat capacity moderates the climate of areas adjacent to the oceans, leading to a maritime climate at such locations. (en.wikipedia.org)
Given the very large heat capacity involved, this would be expected to influence surface temperatures, as has been pointed out many times, but the parameterisation of the ocean heat model would be expected to have a large influence on surface temperatures. (judithcurry.com)