表层海洋中产生的颗粒有机碳(POC)通过水柱下沉,并在深处呼吸,作为在深海海洋中封存碳的主要媒介。大气二氧化碳水平对呼吸将POC转化为无机碳的长度(深度)尺度敏感,因为较浅的水与大气的交换比更深的水更快。然而,对这种碳再生长度尺度及其时空变异性的估计是有限的,阻碍了表征其对环境条件敏感性的能力。这里,我们从热带东部南太平洋的GEOTRACESGP16样带以高垂直和空间分辨率呈现POC通量的带状部分,基于对放射性钍同位素230Th的归一化。我们发现,对于贫营养的南太平洋环流,碳再生长度比以前的估计要浅,表明碳转移到深海的效率较低。在秘鲁海岸附近的低氧水域中,碳再生受到强烈抑制。规范的马丁曲线幂律不足以捕获亚波克斯站的POC通量分布。相反,我们使用指数函数拟合这些轮廓,通量保留在深度,发现浅层再生但低于1,000m的高POC固存。再生长度尺度和深度处的POC通量都密切跟踪氧气浓度接近零的深度。我们的发现表明,气候变暖将导致由于扩张的贫营养回旋而导致的海洋碳储量减少,但是不断扩大的低氧水域对海洋碳储存的相反影响将需要建模和未来的工作来解开。
Particulate organic carbon (POC) produced in the surface ocean sinks through the water column and is respired at depth, acting as a primary vector sequestering carbon in the abyssal ocean. Atmospheric carbon dioxide levels are sensitive to the length (depth) scale over which respiration converts POC back to inorganic carbon, because shallower waters exchange with the atmosphere more rapidly than deeper ones. However, estimates of this carbon regeneration length scale and its spatiotemporal variability are limited, hindering the ability to characterize its sensitivity to environmental conditions. Here, we present a zonal section of POC fluxes at high vertical and spatial resolution from the
GEOTRACES GP16 transect in the eastern tropical South Pacific, based on normalization to the radiogenic thorium isotope 230Th. We find shallower carbon regeneration length scales than previous estimates for the oligotrophic South Pacific gyre, indicating less efficient carbon transfer to the deep ocean. Carbon regeneration is strongly inhibited within suboxic waters near the Peru coast. Canonical Martin curve power laws inadequately capture POC flux profiles at suboxic stations. We instead fit these profiles using an exponential function with flux preserved at depth, finding shallow regeneration but high POC sequestration below 1,000 m. Both regeneration length scales and POC flux at depth closely track the depths at which oxygen concentrations approach zero. Our findings imply that climate warming will result in reduced ocean carbon storage due to expanding oligotrophic gyres, but opposing effects on ocean carbon storage from expanding suboxic waters will require modeling and future work to disentangle.