It looks like a hockey stick to me. I drew up my own curve last summer from NOAA Ocean heat data and the hockey stick fits well.
The cooling trend seen in the 1960s led some of us to build passive solar homes and insulate in anticipation of bigger heating bills in 1970s. Though that is always a useful even with the warming trend.
Ocean heat is a major cause of ice melt for ice sheets and for tidewater glaciers.
I did some calculations from water masses in Glacier Bay and was able to show the melted-ice contribution from seasonal temperature and salinity data. Freshwater ice at zero degrees gives up its latent heat and reduces the salinity and temperature of the fjord. This gives a handle on the quantities involved. It assumes glacial input is mainly ice ignoring the under ice meltwater from higher up the glacier. However since it all started out as ice it gives a good ice of glacial ice contribution to the nearby ocean. [MATTHEWS JB THE SEASONAL CIRCULATION OF THE GLACIER BAY, ALASKA FJORD SYSTEM ESTUARINE COASTAL AND SHELF SCIENCE 12 (6): 679-700 (1981)]
I wonder if anyone has done the same around other tidewater glaciers in Greenland, Chile or Antarctica?