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GLOBAL ENVIRONMENTAL CHANGE: Research Pathways for the Next Decade
and the atmosphere on dec-cen timescales? Can these fluxes be quantified? How can the capability be developed to predict the responses of oceanic biogeochemical processes to anthropogenic perturbations, as these responses relate to dec-cen climate change?
Several observational elements of a dec-cen ocean program must be directed toward elucidating the physics of key phenomena and processes to guide in their representation or parameterization in model simulations, should they not be fully resolvable in those simulations, and to provide a framework to interpret the decadal signals seen in the data and the models. Phenomena and processes need comparable concentrated efforts. For example, an examination is warranted of the special circumstance of mode water formation in the subtropics because it contributes so much of the thermocline volume and because it occurs adjacent to strong current systems, which account for most of the heat released from the ocean to the atmosphere.
Time series stations must be continued and supplemented. Discontinued stations should be reinitiated and new ones established. Sparser happenstance measurements provide limited gap filling for the interrupted stations and a background history for new sites. Improving on ship-based observations, new time series can use moored profiling conductivity-temperature-depth capabilities now coming online and subsurface floats, thereby reducing the need for ship-based support measurements. Continued satellite data are needed for global coverage of sea surface height, SST, winds, and ocean color, calibrated against in situ ocean observations.
The part of the Earth's surface that remains perennially frozen, as well as the part that is near or below the freezing point, constitutes the cryosphere ( “cryo” means cold or freezing), though our working definition of the cryosphere is all forms of frozen water on the land or sea surface, whether admixed (as in permafrost) or pure (as in snow or ice). Thus, this section addresses not only glaciers and sea ice (perennial and seasonal) but also vast areas of frozen ground and permafrost, as well as seasonal snow fields that lie beyond the limits of glaciers.
The cryosphere directly influences climate through enhancing the equator-to-pole thermal gradient by increasing the albedo (radiation reflected from the surface) of the polar regions through vast areas of highly reflective ice and snow fields. The cryosphere also plays a predominant role in sea level; the most vulnerable ice sheet susceptible to potentially rapid destruction is the West Antarctic ice sheet, which contains enough water to raise sea level by 18 m should it melt.