TABLE E.3 Sensitivity of Rapid Dynamic Response Estimate to the Choice of Parameters

Percentage Change Δ mm Sea-Level Rise
Glaciers and ice caps
30 percent of 324.8 GT yr-1 0.99 179
70 percent of 324.8 GT yr-1 1.01 182
     
Greenland Ice Sheet
80 percent of 375.1 GT yr-1 0.9 165
120 percent of 375.1 GT yr-1 1.09 197
     
Antarctic Ice Sheet
80 percent of 264 GT yr-1 0.93 169
120 percent of 264 GT yr-1 1.07 192

NOTE: Input parameters were varied by ± 20 percent individually (only one parameter was varied at a time).

 

TABLE E.4 Effect of Reduced Greenland Dynamic Discharge on Sea-Level Rise Projections

Year Total Sea-Level Rise (mm) Cryosphere Component (mm)
Base-Rate Projection (From Table 5.2)
2030 135 81
2050 280 180
2100 827 584
     
50 Percent Slowdown in Greenland Dynamic Discharge
2030 128 76
2050 273 168
2100 774 535
     
Percent Change
2030 -5% -6%
2050 -3% -7%
2100 -6% -8%

Decreases in Dynamic Discharge

To test the effect of decreased dynamic discharge, the projected output of the Greenland Ice Sheet was reduced by 25 percent from its projected base value and all other cryosphere terms were left unchanged. The results are summarized in Table E.4. The table shows the cumulative sea-level rise (central value only) for 2030, 2050, and 2100 for both the base rate projection (Table 5.2) and for a 50 percent reduction in Greenland calving discharge (equivalent to a 25 percent reduction in overall Greenland discharge). The cryosphere component totals are for the Greenland and Antarctica ice sheets, glaciers, and ice caps, and the total sea-level rise includes the steric component. The percent change rows show that reducing the Greenland discharge affects sea-level projections by a maximum of 8 percent.

EFFECT OF SEA-LEVEL FINGERPRINT

The influence of melting from Alaska, Greenland, and Antarctica on regional sea level was described in “Sea-Level Fingerprints of Modern Land Ice Change” in Chapter 4. To estimate this effect on projected future sea-level rise, land ice loss rates were subdivided into Alaska, Greenland, Antarctic, and all other glacier and ice cap losses other than Alaska. The fingerprint scale factors for Alaska, Greenland, and Antarctica (specified in Table 4.1) were then applied to losses from those regions, on a year-by-year basis, and the losses from other glacier and ice cap regions were carried forward without adjustment. The projected sea level ΔZ at destination region p and time t is then, using the notation defined in Appendix C:



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