南极冰盖的形成与消融对全球大地水准面与海面的影响

IMPACTS OF THE FORMATION AND ABLATION OF ANTARCTIC ICE SHEETS ON THE GLOBAL GEOID AND SEA-LEVEL CHANGES

采用球函数表征了南极冰川覆盖的高度，并运用位理论与地壳均衡观念，研究了南极冰盖形成、消融对大地水准面与相对海面的影响。结果表明，冰盖形成后的大地水难面发生了明显变化，在南极为＋115m，在南纬25°带上为－37m，在北极为＋8m；若地壳为弹性固体而地幔为流体，设地慢密度为3270kg／m3，则在冰川消融、地壳均衡调整后的沿海大陆相对海面的变化仅为2．8m。

It is convenient to investigate into the gravimetry using a harmonic spheric funtionwhich describe the distribution and thickness of the Antarctic ice sheet. The gravitational theory andthe Stokes' harmonic spheric funtion formula were used to determine the impact of the Antarctic icecap on the global geoid. The Antarctic ice cap is formed from the condensation of seawater vapourwhose mass is equal to a layer of seawarer 59m thick of covering the earth's surfase, i.e. 2.7 x 1019kg. This will cause the global averaged geoid to decrease for around 23m. The authors'computations show that the Antractic ice cap has a great impact on the global geoid, which increases(+) in some regions, but decreases (-) in other regions. The geoid is + 115m, -37m and +8m at the South Pole, the 25°S parallel and the North Pole, respectively. If the Antarctic ice capmelts complctely, on the rigid Earth's surface the seawater and geoid will retum to its originalposition (and height) due to the balancing fome of the fluld.Since the crust is almost in a state of isosthey, assuming that the crust is an elastic solid andthe mantle is an imcompressive fluid, the load of seawater will deflect the crust and drive themane material to flow. The matorial above the isostatic surface compensares mutually. If thedensities of the mantle and seawater are 3 270kg /m3 and 1230kg / m3, respectively, then thevariation in the elevation of the continent is only 2.8m with respect to the sea level after theAntarctic ice cap melts.It is worth noting that the above results were derived from an ideal Earth model. in the realEarth, the mantle and crust are visco-elastic.