de Melo Viríssimo Francisco, Martin Adrian P, Henson Stephanie A
National Oceanography Centre Southampton UK.
Global Biogeochem Cycles. 2022 Feb;36(2):e2021GB007101. doi: 10.1029/2021GB007101. Epub 2022 Feb 7.
The biological carbon pump is a key component of the marine carbon cycle. This surface-to-deep flux of carbon is usually assumed to follow a simple power law function, which imposes that the surface export flux is attenuated throughout subsurface waters at a rate dictated by the parameterization exponent. This flux attenuation exponent is widely assumed as constant. However, there is increasing evidence that the flux attenuation varies both spatially and seasonally. While the former has received some attention, the consequences of the latter have not been explored. Here we aim to fill the gap with a theoretical study of how seasonal changes in both flux attenuation and sinking speed affect nutrient distributions and carbon fluxes. Using a global ocean-biogeochemical model that represents detritus explicitly, we look at different scenarios for how these varies seasonally, particularly the relative "phase" with respect to solar radiation and the "strength" of seasonality. We show that the sole presence of seasonality in the model-imposed flux attenuation and sinking speed leads to a greater transfer efficiency compared to the non-seasonal flux attenuation scenario, resulting in an increase of over 140% in some cases when the amplitude of the seasonality imposed is 60% of the non-seasonal base value. This work highlights the importance of the feedback taking place between the seasonally varying flux attenuation, sinking speed and other processes, suggesting that the assumption of constant-in-time flux attenuation and sinking speed might underestimate how much carbon is sequestered by the biological carbon pump.
生物碳泵是海洋碳循环的关键组成部分。这种碳从表层到深层的通量通常被认为遵循一个简单的幂律函数，这意味着表层输出通量在整个次表层水域中以参数化指数所决定的速率衰减。这个通量衰减指数被广泛假定为常数。然而，越来越多的证据表明，通量衰减在空间和季节上都会发生变化。虽然前者已经受到了一些关注，但后者的影响尚未得到探讨。在这里，我们旨在通过一项理论研究来填补这一空白，该研究关注通量衰减和下沉速度的季节性变化如何影响营养物质分布和碳通量。我们使用一个明确表示碎屑的全球海洋生物地球化学模型，研究这些因素在季节上的不同变化情况，特别是相对于太阳辐射的相对“相位”和季节性的“强度”。我们表明，与非季节性通量衰减情况相比，模型中通量衰减和下沉速度的季节性变化单独存在时会导致更高的传输效率，当所施加的季节性幅度为非季节性基础值的60%时，在某些情况下会导致超过140%的增加。这项工作突出了季节性变化的通量衰减、下沉速度与其他过程之间反馈的重要性，表明通量衰减和下沉速度随时间恒定的假设可能低估了生物碳泵所封存的碳量。
