Juncheng Zuo

Assessing the global averaged sea-level budget from 2003 to 2010

A global mass balance (Greenland and Antarctica ice sheet mass loss, terrestrial water storage) and different sea-level components (observed sea-level from satellite altimetry, steric sea-level from Ishii data, and ocean mass from gravity recovery and climate experiment, GRACE) are estimated, in terms of seasonal and interannual variabilities from 2003 to 2010. The results show that a detailed analysis of the GRACE time series over the time period 2003–2010 unambiguously reveals an increase in mass loss from the Greenland ice sheet and Antarctica ice sheet. The mass loss of both ice sheets accelerated at a rate of (392.8±70.0) Gt/a during 2003–2010, which contributed (1.09±0.19) mm/a to the globalmean sea-level during this time. The net terrestrial water storage (TWS) trend was negative over the 8 a time span, which gave a small positive contribution of (0.25±0.12) mm/a. The interannual variability of the globalmean sea-level was at least partly caused by year-to-year variability of land water storage. Estimating GRACE-based ice sheet mass balance and terrestrial water storage by using published estimates for melting glaciers, the results further show that the ocean mass increase since 2003 has resulted half from an enhanced contribution of the polar ice sheets, and half from the combined ice sheet and terrestrial water storage loss. Taking also into account the melting of mountain glaciers (0.41 mm/a) and the small GRACE-based contribution from continental waters (0.25 mm/a), a total ocean mass contribution of (1.75±0.57) mm/a from 2003 to 2010 is found. Such a value represented 75% of the altimetry-based rate of sea-level rise over that period. The contributions to steric sea-level (i.e., ocean thermal expansion plus salinity effects) are estimated from: (1) the difference between altimetry-based sea-level and ocean mass change and (2) the latest Ishii data. The inferred steric sea-level rate from(1) (1.41 mm/a from 2003 to 2010) did not agree well with the Ishii-based value also estimated here (0.44 mm/a from 2003 to 2010), but phase. The cause for such a discrepancy is not yet known but may be related to inadequate sampling of in situ ocean temperature and salinity measurements.

Role of surface warming in the northward shift of tropical cyclone tracks over the South China Sea in November

Tropical cyclones (TCs) formed in the Northwest Pacific Ocean (NWP) can cross the South China Sea (SCS) sometimes. It is found that the TC tracks in the SCS in November are shifted to the north after 1980 compared with those before 1980. Both data analyses and numerical simulations show that the surface warming in the SCS may contribute to this more northward shift. The warming produces a cyclonic atmosphere circulation anomaly in the northwestern SCS and an associated southerly in the central SCS steering the TCs to the north.

Responses of estuarine salinity and transport processes to sea level rise in the Zhujiang (Pearl River) Estuary

Understanding the changes of hydrodynamics in estuaries with respect to magnitude of sea level rise is important to understand the changes of transport process. Based on prediction of sea level rise over the 21st century, the Zhujiang (Pearl River) Estuary was chosen as a prototype to study the responses of the estuary to potential sea level rise. The numerical model results show that the average salt content, saltwater intrusion distance, and stratification will increase as the sea level rises. The changes of these parameters have obvious seasonal variations. The salt content in the Lingdingyang shows more increase in April and October (the transition periods). The saltwater intrusion distance has larger increase during the low-flow periods than during the high-flow periods in the Lingdingyang. The result is just the opposite in Modaomen. The stratification and its increase are larger during the low-flow periods than during the high-flow periods in Lingdingyang. The response results of transport processes to sea level rise demonstrate that: (1) The time of vertical transport has pronounced increase. The increased tidal range and currents would reinforce the vertical mixing, but the increased stratification would weaken the vertical exchange. The impact of stratification changes overwhelms the impact of tidal changes. It would be more difficult for the surface water to reach the bottom. (2) The lengthways estuarine circulation would be strengthened. Both the offshore surface residual current and inshore bottom residual current will be enhanced. The whole meridional resident flow along the transect of the Lingdingyang would be weakened. These phenomena are caused by the decrease of water surface slope (WWS) and the change of static pressure with the increase of water depth under sea level rise.

Role of ocean upper layer warm water in the rapid intensification of tropical cyclones: A case study of typhoon Rammasun (1409)

Rammasun intensified rapidly from tropical storm to super typhoon in the northern South China Sea (NSCS) before its landfall on Hainan Island. Analysis of observed data shows that the anomalous ocean upper layer warm water (WW) is important to the rapid intensification of Rammasun. During the period of Rammasun, sea surface temperature (SST) in the NSCS was much warmer than the climatological SST. The anomalous WW supplied more energy to Rammasun, resulting in its rapid intensification. Numerical simulations further confirm that the NSCS WW plays an important role in the rapid intensification of Rammasun. As the WW is removed, the intensification of Rammasun is only 25 hPa, which is 58.1% of that in the original SST-forced run.

Establishment of ocean dumping area capacity assessment model

Dumping area capacity is mainly affected by the hydrodynamic process (tidal sediment, storm surge and wave, etc.) as well as the size and depth of dumping area. Based on three-dimensional ocean circulation model known as FVCOM (Finite Volume Coast and Ocean Model) and the stochastic dynamic statistical analysis model, taking advantage of dumping ground topography evolution and dumping quantity, the author aims to discuss the influence of hydrodynamic processes and dumping activity so as to built a new model of ocean dumping area capacity. With the data of depth and dumped amount in the dumping area, the changes of bottom topographic which caused by tidal current under the natural condition based on the FVCOM hydrodynamic and sediment module, the author strive to analyze the statistical relation of the changes for dumping amount, tidal current and bottom topographic. Through real data to fit revision coefficient values, which will be regarded as topographic changes reference value affected by wave and storm surges. Thus taking this evaluation as the long-term changes in the dumping capacity. In the premise of setting up the threshold of bottom topographic changes, the dumping area capacity is calculated. Take Yangtze Estuary No. 1 dumping area as an example, As the water depth reduces by 0.5 m annually, the dumping area capacity is about 6.7 million m3/a, the model results are in reasonable agreement with the actual amount. Then the model is validated in Luoyuan Bay dumping area, Shengsishangchuan Mountain dumping area, Dongding dumping area, Dongshan dumping area, and Wenzhou Port dumping area, it is turns out the results are similar to that of the actual observations.