Holocene Sea-level Change in the Caribbean: Implications for Geophysical Modeling and Ocean-Climate Interactions

记录1万年的海平面变化，以更好地了解21世纪的海平面上升史密森学会该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。为了预测现在和未来海岸的快速演变，我们必须首先重建当地相对海平面上升的长期速度，以应对非人为气候变化，并记录珊瑚礁-红树林环境随时间变化的能力，以跟上这些变化的速度。地质稳定的加勒比区域是最合适的自然环境，拥有最高质量的红树林泥炭和珊瑚礁沉积物。红树林泥炭是一种生物沉积物，是沿海环境变化的可靠长期指标。热带浅海珊瑚礁和红树林生态系统对气候和海平面变化的速率很敏感。因此，这些相互关联的环境的空间范围和健康受到快速环境变化的影响。因此，这些环境的变化会影响沿海人口和依赖它们的渔业的生存能力。鉴于沿海地区人口和经济活动的大量和日益集中，以及沿海生态系统的重要性，海平面上升的潜在影响在二十多年来引起了广泛关注。需要对前卫星时代的海平面上升进行准确估计，以便为这些21世纪的估计提供背景并校准气候模式。在20世纪，潮汐计记录的全球海平面上升速度为每年1.7至1.8毫米。然而，潮汐计的数量、分布和持续时间有限，阻碍了对气候-海平面假设进行有力检验和建立导致变化的驱动机制的努力。随着海平面研究的最新进展，这些仪器记录可以与红树林和珊瑚沉积序列的海平面记录相补充。一个由资深科学家及其学生组成的跨学科小组将编制一个质量控制的、空间和时间上全面的加勒比海平面数据库，以重建珊瑚礁和潮间带红树林同时记录的海平面变化。我们将集中精力从厚厚的红树林泥炭沉积物中收集全新世（过去1万年）的新海平面指数点，并进行精确的高程测量。海平面指标点的垂直精度将受到微化石组合的限制，指标点将使用最新的加速器质谱（AMS）方法进行放射性碳测年。这些资料将产生厘米至日米尺度垂直分辨率和百年至十年尺度时间分辨率的海平面重建。这一全面的记录将使我们能够破译海洋温度和盐度变化、冰盖质量变化以及固体地球对全新世海平面变化的均衡响应的影响。更近期的红树林沉积物将使用同位素方法进行更详细的分析，以弥补仪器和已建立的海平面变化地质记录之间的差距。这些数据是未来模拟实验的关键变量，用于评估沿海地区对海平面变化的反应，为国家和区域灾害评估提供信息，并更好地了解海平面上升与沉积物供应和风/波过程相互作用的当地地貌反应。

Documenting 10,000 years of sea-level change to better understand 21st century sea-level riseMarguerite Toscano, Smithsonian InstitutionThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). To predict present and future rapid coastal evolution, we must first reconstruct the long-term rates of local-relative sea-level rise in response to non-anthropogenic climate change, and document the ability of coral reef-mangrove environments to keep pace with these varying rates over time. The geologically stable Caribbean region is the most appropriate physical setting, containing the highest-quality mangrove peat and coral reef deposits for this purpose. Mangrove peat is a biogenic deposit that is a reliable long-term indicator of changing coastal environments. The shallow tropical marine coral reef and mangrove ecosystem is sensitive to varying rates of climate and sea-level changes. As such, the spatial extent and health of these interconnected environments are impacted by rapid environmental change. Therefore, alterations in these environments impact the viability of coastal populations and fisheries that depend on them. Given the large and growing concentration of population and economic activity in the coastal zone, as well as the importance of coastal ecosystems, the potential impacts of sea-level rise have elicited widespread concern for more than two decades. Accurate estimates of sea-level rise in the pre-satellite era are needed in order to provide a context for these 21st century estimates and calibrate climate models. During the 20th century the global rate of sea-level rise recorded by tide gauges was 1.7 to 1.8 mm/yr. However, the limited number, distribution and duration of tide gauges preclude efforts to test robustly the climate-sea level hypotheses and establish the driving mechanisms responsible for change. With recent advances in sea-level studies, these instrumental records can be augmented with sea-level records derived from mangrove and coral sedimentary sequences.An interdisciplinary team of senior scientists and their students will produce a quality-controlled, spatially and temporally comprehensive Caribbean sea-level database to reconstruct sea-level changes recorded simultaneously by coral reefs and intertidal mangroves. We will concentrate on collecting new sea-level index points for the Holocene (last 10,000 years) from thick mangrove peat deposits, with precision elevation measurements. The vertical precision of sea-level index points will be constrained by microfossil assemblages and the index points will be radiocarbon dated using the latest Accelerator Mass Spectrometric (AMS) methods. These data will produce a sea-level reconstruction at cm to dm scale vertical resolution and centennial to decadal scale temporal resolution. This comprehensive record will allow us to decipher the influence of ocean-temperature and salinity changes, mass changes of ice sheets and the isostatic response of the solid earth to Holocene sea-level changes. More recent mangrove sediments will be analyzed in greater detail using isotopic methods to bridge the gap between instrumental and established geologic records of sea-level change. Such data are a key variable in future modeling experiments to assess coastal response to sea-level change, inform national and regional hazard assessments and better understand local geomorphologic responses where sea-level rise interacts with sediment supply and wind/wave processes.