Titel: Sea Level Variations derived from Mass Conserving Finite Element Sea-Ice Ocean Model; Untertitel: Study of Major Contributions to Sea Level Change in the Recent Past

Abstract

During the last century sea level rise strongly increased compared to sea level change in the last 2000 years. The present study investigates global and regional sea level change, simulated with the finite element sea-ice ocean model (FESOM). The major goal is to separate sea level change into steric and eustatic contributions and to estimate the influence of Greenland and Antarctic ice sheet melt on global and regional sea level. Modeled steric height variations show realistic regional geophysical patterns compared with steric height variations derived from altimetry measurements and GRACE. Compared to the time before the 1990 s, an increased global trend in steric sea level rise is found in estimates derived from the model and from satellite measurements. Modeled ocean mass exhibits reasonable spatial structures. However, the trend in the global model mean cannot be trusted in FESOM as it strongly depends on the mass budget of the model, which is determined by uncertain mass fluxes. To account for this, global mean ocean mass variations need to be optimized to realistic values. To this end results from GRACE in combination with GPS data is used. Greenland and Antarctic ice sheet melting influence the global sea level mainly through the additional mass. The eustatic sea level rises by about 0.3 mm/yr for 100 Gt/yr of melt water. Additionally, the fresh water causes local steric variations in sea level that are transported farther by ocean currents. The ice sheet mass loss yields a decrease in gravitational attraction causing a sea level fall near the source of mass loss but also to a slight increase at long distance. This effect is computed for the Greenland ice sheet mass loss using Green s functions. It leads to a decreased sea level near the Greenland coast and to a slightly increased sea level in the Southern Ocean. The effect of different melting scenarios is investigated.