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Isotopic characterisation of nutrient dynamics and UCDW behaviour in the west Antarctic Peninsula sea ice environment

南极半岛西部海冰环境营养物动态和 UCDW 行为的同位素表征

基本信息

批准号：
NE/K010034/1
负责人：
Sian Henley
金额：
$ 54.51万
依托单位：
University of Edinburgh
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FK010034%2F1
关键词：
Isotopic characterisation nutrient dynamics UCDW

项目摘要

This research project aims to examine the ways in which ongoing climate change and sea ice decline at the west Antarctic Peninsula (WAP) are impacting upon nutrient budgets and biogeochemical cycling throughout the region. The WAP is an ecologically important region of high primary productivity, and nutrient cycling is known to be crucial to phytoplankton production and its relationship with CO2 dynamics. Upper circumpolar deep water (UCDW) is understood to constitute the principal source of nutrients to surface waters throughout the WAP region. UCDW incurs at the shelf break and is transported across the continental shelf, so that nutrients can be supplied to the mixed layer by vertical mixing. This source of nutrients fuels high productivity in coastal regions, with implications for the biological uptake of atmospheric CO2.Available evidence suggests that sea ice variability can drastically impact phytoplankton biomass and nutrient utilisation in surface waters during the summer growing seasons, but the mechanisms underlying this interaction remain to be fully understood. Sea ice melt and meteoric freshwater inputs can promote phytoplankton blooms by stabilising the upper ocean sufficiently to provide a well-lit surface environment conducive to growth. However, such stratified conditions can also inhibit productivity and the magnitude of the bloom by restricting the resupply of nutrients to the mixed layer. Superimposed onto large interannual variability in chlorophyll, macronutrients and the physical environment, there are strong indications of long-term sea ice decline along the WAP and a concomitant decline in productivity.This research project seeks to understand the changes in nutrient biogeochemistry underlying these changes in productivity in the WAP sea ice zone, and addresses the central hypothesis that a climate-induced reduction in sea ice and stratification will result in drastic declines in primary production and nitrate utilisation in the surface environment. Such conditions would lead to a simultaneous reduction in the capacity of the oceanic CO2 sink during summer and generate an increased pool of unutilised nitrate in surface waters over the shelf, both of which would hold profound implications for global biogeochemical cycles.This study will comprise three components:1. A time-series study over three austral summer growing seasons in Ryder Bay, WAP, to examine temporal changes in fixed nitrogen budgets and cycling, in relation to interannual variability in sea ice, water column structure and productivity.2. A ship-based transect from the shelf break to Marguerite Bay to examine deep water behaviour and its impact on the supply of nutrients to high productivity coastal regions.3. Ship-based sampling across the wider WAP shelf region to examine spatial variability in nutrient dynamics, productivity, sea ice and physical oceanography, and give a broader context to the time-series study.A suite of biogeochemical measurements pertinent to nutrient budgets and cycling will be made during each component of the study. Comprehensive ancillary physical and biological data are available from project partners, to examine productivity and environmental variables alongside these nutrient measurements. A fixed nitrogen budget will be constructed for the WAP shelf on an annual basis and its interannual variability examined in the context of ongoing sea ice losses and changes in phytoplankton productivity. Nutrient biogeochemistry is central to the relationship between productivity and oceanic uptake of atmospheric CO2, so this study has broad and far-reaching implications for the role of the Southern Ocean CO2 system in regulating global climate. This study will also help to predict the future response of the oceans to ongoing climate change at the wider scale by giving insight into the climatic impacts on nutrient cycling and productivity in the fastest-warming marine environment on Earth.

该研究项目旨在研究南极半岛（WAP）西部持续的气候变化和海冰减少对整个地区营养收支和生物地球化学循环的影响。WAP是一个生态上重要的高初级生产力的区域，营养循环是已知的浮游植物生产及其与CO2动态的关系至关重要。据了解，上环极深水是整个WAP区域表层沃茨营养物质的主要来源。UCDW产生于陆架坡折处，并通过陆架输送，营养盐通过垂直混合作用进入混合层。这一营养源为沿海地区的高生产力提供了燃料，并对大气CO2的生物吸收产生了影响。现有证据表明，海冰的变化会在夏季生长季节对表层沃茨的浮游植物生物量和营养利用产生巨大影响，但这种相互作用的机制仍有待充分理解。海冰融化和大气淡水输入可以通过稳定上层海洋来促进浮游植物的大量繁殖，从而提供有利于生长的良好光照的表面环境。然而，这样的分层条件也可以通过限制营养物向混合层的再供应来抑制生产力和水华的程度。叠加在叶绿素、常量营养素和物理环境的巨大年际变化上，有强烈的迹象表明，沿着WAP海冰长期减少，生产力也随之下降。本研究项目旨在了解WAP海冰区生产力变化背后的营养盐地球化学变化，和地址的核心假设，气候引起的海冰和分层的减少将导致急剧下降的初级生产和硝酸盐利用在表面环境。这种情况将导致夏季海洋CO2汇容量的同时减少，并在大陆架上方的表层沃茨中产生更多未利用的硝酸盐，这两者都将对全球海洋地球化学循环产生深远的影响。对WAP莱德湾三个夏季生长季节的时间序列研究，以研究固定氮收支和循环的时间变化，以及海冰、水柱结构和生产力的年际变化。从陆架断裂到玛格丽特湾的船基样带，以检查深水行为及其对高生产力沿海地区营养物供应的影响。在更广泛的WAP大陆架区域进行船基采样，以检查营养动态、生产力、海冰和物理海洋学的空间变异，并为时间序列研究提供更广泛的背景。项目合作伙伴可提供全面的辅助物理和生物数据，以检查生产力和环境变量以及这些营养测量。将每年为WAP大陆架建立一个固定的氮收支，并在海冰不断减少和浮游植物生产力变化的背景下审查其年际变化。营养盐地球化学是生产力和海洋吸收大气CO2之间关系的核心，因此这项研究对南大洋CO2系统在调节全球气候中的作用具有广泛而深远的影响。这项研究还将有助于预测海洋未来对更大范围的持续气候变化的反应，使人们了解气候对地球上变暖最快的海洋环境中的营养循环和生产力的影响。