南大洋酸化过程及其变化趋势研究进展

REVIEW OF OCEAN ACIDIFICATION PROCESSES AND CHANGING TRENDS IN THE SOUTHERN OCEAN

近30年的集成研究表明,南大洋吸碳能力从20世纪90年代开始出现明显的下降,但是这种减弱趋势在2002年后又开始转变为显著增强的趋势,展现出一种吸收大气中人为CO2更强的能力,这种态势伴随着南大洋的酸化进一步增强。观测表明,开阔大洋(45°S-50°S)在1991-2000年间的pH下降速率为每年0.0007,文石饱和度Ω文石以每年0.015的速率上升,而在2001-2011年间pH下降速率增大为每年0.0024,Ω文石转变为每年0.017的下降速率。在南大洋近岸海域,海洋酸化程度区域性差别很大,影响因素也更加复杂。例如,普里兹湾在1994-2010年pH和Ω文石分别下降了0.11和0.30,威德尔海在1978-2008年间的表层海水pH下降速率为每年0.0011,Ω文石下降速率为每年0.002。基于现场观测数据和遥感反演参数方法,从点线观测数据评估扩展到海区整体范围的南大洋酸化趋势评估取得了重要进展。而近期改进的模型模拟与观测结果比较在量级和更大尺度空间上都取得了较好的结果。本文对地球系统模型(ESM)预测的包括RCP 8.5等不同情境下的南大洋酸化趋势以及海洋酸化对南大洋生态系统的效应进行综合评述,结果表明到本世纪末南大洋大部分海域都将处于文石不饱和状态,预示着南大洋的酸化进展将会严重影响海洋生物地球化学变化和损坏整个南大洋的生态系统。因此,对南大洋开展海洋酸化过程、驱动机制和预测研究以及生态效应评估已严肃地摆在全人类的面前。

Integrated studies over the past 30 years have shown that the carbon absorption capacity of the Southern Ocean has declined significantly since the 1990 s. But this weakening trend began to change significantly with an increasing trend after 2002, showing a stronger ability to absorb anthropogenic CO2 in the atmosphere, which will be further enhanced with acidification of the Southern Ocean. Observations show that the decline rate of pH in the Open Southern Ocean of 45°-50°S was 0.0007 per year during 1991–2000, and the Ωarag rose at a rate of 0.015 per year. The decline rate of pH increased to 0.0024 per year during 2001–2011, the Ωarag turned to decline at a rate of 0.017 per year. However, regional differences in ocean acidification among the coastal waters of the Southern Ocean are very large and the interaction of various influencing factors is more complex. For example, the pH and Ωarag in Prydz Bay dropped by approximately 0.11 and 0.30, respectively, from 1994 to 2010. Observations collected in the Weddell Sea from 1973 to 2008 show a decrease in pH on the order of 0.0011 units per year in surface waters associated with a reduction in Ωarag at a rate of 0.002 units per year. Based on the in situ observations and remote sensing inversion parameter methods, important progress has been made in assessing the acidification trend of the Southern Ocean from point-line observations to the overall extent of the sea area. Recently improved model simulation results likewise shown good agreement with the observation results in both magnitude and large-scale spatial patterns. This paper also reviews the acidification trend in the Southern Ocean under different scenarios including RCP 8.5 predicted by the Earth System Model(ESM) and the effects of ocean acidification on the ecosystem of the Southern Ocean. Results show that most of the Southern Ocean will be in an aragonite undersaturated state by the end of this century, indicating that the acidification progress of the southern ocean will seriously affect the marine biogeochemical changes and damage the ecosystem of the entire Southern Ocean. Therefore, the study of ocean acidification processes, driving mechanisms and prediction, as well as the evaluation of the ecological effects of this acidification in the Southern Ocean have been seriously placed in front of all mankind.