Ocean Carbon Export Flux Projections in CMIP6 Earth System Models Across Multiple Export Depth Horizons

IF 5.4 2区 地球科学 Q1 ENVIRONMENTAL SCIENCES
Stevie L. Walker, Hilary I. Palevsky
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引用次数: 0

Abstract

The ocean's biological carbon pump (BCP) plays a key role in global carbon cycling by transporting biologically fixed carbon from the surface to the deep ocean. Prior analyses of the BCP in Earth System Model (ESM) simulations have typically evaluated particulate organic carbon (POC) flux at a fixed export depth horizon of 100 m. However, this overlooks spatial and temporal variations in the depth that sinking POC must penetrate to reach the mesopelagic or to sequester carbon from the atmosphere on climate-relevant timescales. We use depth-resolved POC flux output from eight Coupled Model Intercomparison Project Phase 6 (CMIP6) ESMs to compare global and regional changes in POC flux at five export depth horizons −100 m, the base of the euphotic zone (EZ depth), the particle compensation depth (PCD), the maximum annual mixed layer depth (MLDmax), and 1,000 m—under the high-emissions scenario SSP5-8.5. We also examine the relationship among net primary production, export efficiency from the surface ocean, and transfer efficiency to depth in key regions of the ocean, identifying model- and region-specific variations in the mechanistic drivers of POC flux changes in the deep ocean. Globally and spatially, trends in POC flux magnitude and decline are similar at the four surface export depth horizons, and multimodel variability in POC flux change by 2100 is greatest at the 1,000 m export depth horizon (+4% to −55%). This indicates the importance of improving model parameterizations of transfer efficiency and POC flux to the deep ocean.

Abstract Image

CMIP6地球系统模式跨多个输出深度的海洋碳输出通量预估
海洋的生物碳泵(BCP)通过将生物固定碳从海洋表面输送到海洋深处,在全球碳循环中起着关键作用。先前对地球系统模式(ESM)模拟中BCP的分析通常是在固定的出口深度水平为100 m时评估颗粒有机碳(POC)通量。然而,这忽略了下沉的POC在与气候相关的时间尺度上到达中上层或从大气中固碳所必须穿透的深度的时空变化。我们利用8个耦合模式比对项目第6阶段(CMIP6) esm的深度分辨POC通量输出,比较了SSP5-8.5高排放情景下,在5个出口深度层(−100 m)、基带(EZ深度)、粒子补偿深度(PCD)、年最大混合层深度(MLDmax)和1000 m的全球和区域POC通量变化。我们还研究了净初级产量、海洋表层输出效率和海洋关键区域向深海转移效率之间的关系,确定了深海POC通量变化机制驱动因素的模式和区域特异性变化。在全球和空间上,四个地表出口深度层的POC通量大小和下降趋势相似,到2100年,1000 m出口深度层的POC通量变化的多模式变率最大(+4%至- 55%)。这表明了改进模式参数化传输效率和向深海的POC通量的重要性。
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来源期刊
Global Biogeochemical Cycles
Global Biogeochemical Cycles 环境科学-地球科学综合
CiteScore
8.90
自引率
7.70%
发文量
141
审稿时长
8-16 weeks
期刊介绍: Global Biogeochemical Cycles (GBC) features research on regional to global biogeochemical interactions, as well as more local studies that demonstrate fundamental implications for biogeochemical processing at regional or global scales. Published papers draw on a wide array of methods and knowledge and extend in time from the deep geologic past to recent historical and potential future interactions. This broad scope includes studies that elucidate human activities as interactive components of biogeochemical cycles and physical Earth Systems including climate. Authors are required to make their work accessible to a broad interdisciplinary range of scientists.
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