Interesting. It'd help much to have a legend for which concentrations correspond to those colors... How big is the difference, in ppb?
For ACI melting season, CH4 releases from land permafrost regions are quite a bit relevant thing, however, there is no massive "mode change". Last 3 million years or so, with long-term temperature trend being some -0.7°C every million year, there was gradual accumulation of clathrates in both land permafrosts and seabed deposits, overall. However, each summer during inter-glacials, land permafrosts had all the sunlight warming things up just like it happens nowadays, - i mean whereever snow cover was absent during the summer, of course, so no big difference in terms of albedo to present day. With summer snow cover gradually retreating, and accumulation of heat from year to year, certainly levels gradually rise. So while it is something we could talk about in terms of how much it affects this melting season in compare, say, to some 1980 or some 1750, etc, - this is relatively minor thing.
The ESS bothers me so much because until very recently (this century), ESAS usually remained ice-covered for much of the summer, which protected seabed clathrates from most of summer's direct insolation (ESS is shallow enough waters for that), and also kept whatever little CH4 is released from entering the athmosphere (most of it, anyway). On top of those differencies, CH4 emitted from land permafrosts has to move quite a distance to start doing its GHE over sea ice, some of it oxidizes on its way, wind often blows "the other direction", etc, - while CH4 which goes into the athmosphere right from the seabed is instantly there, starting to produce its GHE very moment it escapes water, if it's sunny weather. Which is why i dare write about ESAS CH4 concern in this topic, but not so much about land permafrosts (which are of course very important part for many other topics and matters other than this melting season, especially long-term).