little over one half (1993-2003; Bindoff et al., 2007). The absorption of heat energy by the oceans varies from place to place on interannual and decadal time scales, and the warmer waters of the tropics and near the ocean surface expand more in response to a given temperature increase than the cold waters at high latitude and at depth (Fofonoff, 1985). Monitoring spatial and temporal heat content changes of the ocean is thus important for predicting both the global average and spatial patterns of future sea level rise, as is developing a better understanding of mixing processes that distribute heat in the oceans.

Land ice contained in the world’s glaciers and ice sheets contributes directly to sea level rise through melt or the flow of ice into the sea (Figure 7.4). In contrast, when sea ice, which is already floating on the ocean surface, melts, it contributes only a negligible amount to sea level rise (Jenkins and Holland, 2007; Noerdlinger and Brower,

FIGURE 7.4 Outlet glaciers in Northwest Greenland. SOURCE: Photo by K. Steffen.