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Enhancement of the North Atlantic CO2 sink by Arctic Waters
Biogeosciences ( IF 4.9 ) Pub Date : 2020-08-27 , DOI: 10.5194/bg-2020-313
Jon Olafsson , Solveig R. Olafsdottir , Taro Takahashi , Magnus Danielsen , Thorarinn S. Arnarson

Abstract. The North Atlantic north of 50° N is one of the most intense ocean sink areas for atmospheric CO2 considering the flux per unit area, 0.27 Pg-C yr−1, equivalent to −2.5 mol C m−2 yr−1. The Northwest Atlantic Ocean is a region with high anthropogenic carbon inventories. This is on account of processes which sustain CO2 air-sea fluxes, in particular strong seasonal winds, ocean heat loss, deep convective mixing and CO2 drawdown by primary production. The region is in the northern limb of the Global Thermohaline Circulation, a path for the long term deep sea sequestration of carbon dioxide. The surface water masses in the North Atlantic are of contrasting origins and character, on the one hand the northward flowing North Atlantic Drift, a Gulf Stream offspring, on the other hand southward moving cold low salinity Polar and Arctic Waters with signatures from Arctic freshwater sources. We have studied by observations, the CO2 air-sea flux of the relevant water masses in the vicinity of Iceland in all seasons and in different years. Here we show that the highest ocean CO2 influx is to the Arctic and Polar waters, respectively, −3.8 mol C m−2 yr−1 and −4.4 mol C m−2 yr−1. These waters are CO2 undersaturated in all seasons. The Atlantic Water is a weak or neutral sink, near CO2 saturation, after poleward drift from subtropical latitudes. These characteristics of the three water masses are confirmed by data from observations covering 30 years. We relate the Polar and Arctic Water persistent undersaturation and CO2 influx to the excess alkalinity derived from Arctic sources, particularly the Arctic rivers. Carbonate chemistry equilibrium calculations indicate clearly that the excess alkalinity may support a significant portion of the North Atlantic CO2 sink. The Arctic contribution to the North Atlantic CO2 sink which we reveal is previously unrecognized. However, we point out that there are gaps and conflicts in the knowledge about the Arctic alkalinity budget and that future trends in the North Atlantic CO2 sink are connected to developments in the rapidly warming Arctic. The results we present need to be taken into consideration for the question: Will the North Atlantic continue to absorb CO2 in the future as it has in the past?

中文翻译:

北极水域增强北大西洋CO 2

摘要。考虑到每单位面积的通量为0.27 Pg-C yr -1,相当于-2.5 mol C m -2  yr -1,北大西洋50°N以北是大气CO 2最密集的海洋汇聚区之一。西北大西洋是一个具有大量人为碳资源的地区。这是由于维持CO 2气-海通量的过程所致,特别是强烈的季节性风,海洋热损失,深对流混合和CO 2初级生产的亏损。该地区位于全球热盐环流的北端,这是长期深海隔离二氧化碳的一条途径。北大西洋的地表水水体具有不同的起源和特征,一方面是北流北大西洋漂流,是墨西哥湾流的后代,另一方面是向南移动的低盐度极地和北极水,具有北极淡水源的特征。通过观察,我们研究了冰岛附近各个季节和不同年份的相关水团的CO 2气-海通量。在这里,我们表明最高的海洋CO 2流入量分别是-3.8 mol C m -2  yr -1和北极和极地水和-4.4 mol C m -2  yr -1。这些水在所有季节都是饱和的CO 2。从亚热带纬度向极点漂移后,大西洋水是一个弱或中性的汇,接近CO 2饱和度。这三个水团的这些特征已得到30年观测数据的证实。我们将极地和北极水的持续欠饱和和CO 2涌入与源于北极,特别是北极河流的过量碱度联系起来。碳酸盐化学平衡计算清楚地表明,过量的碱度可能支持北大西洋CO 2汇的很大一部分。北极对北大西洋CO 2的贡献我们揭示的接收器以前无法识别。但是,我们指出,关于北极碱度预算的知识存在差距和冲突,并且北大西洋CO 2汇的未来趋势与迅速变暖的北极的发展有关。需要考虑以下问题:我们目前的结果:北大西洋将来会像过去一样继续吸收CO 2吗?
更新日期:2020-08-27
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