Persistent Ocean Anomalies as a Response to Northern Hemisphere Heating Induced by Biomass Burning Variability
Persistent Ocean Anomalies as a Response to Northern Hemisphere Heating Induced by Biomass Burning Variability
复制标题
持续的海洋异常是对生物质燃烧变异引起的北半球加热的反应
DOI：
10.1175/jcli-d-23-0090.1
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发表时间：
2023
影响因子：
4.9
通讯作者：
Danabasoglu, Gokhan
中科院分区：
文献类型：
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作者：
Yamaguchi, Ryohei;Kim, Ji-Eun;Rodgers, Keith B.;Stein, Karl;Timmermann, Axel;Lee, Sun-Seon;Huang, Lei;Stuecker, Malte F.;Fasullo, John T.;Danabasoglu, Gokhan
与早期相比，耦合模式对比项目第六阶段(CMIP6)历史强迫场中的生物质燃烧气溶胶(BBA)排放在1997-2014年期间增强了时间变率。最近的研究证明，在这段时间内，相应的非均匀短波强迫可以引起云、永久冻土和土壤湿度的变化，这有助于相对于早期时期的北半球陆地净变暖。在这里，我们研究了海洋对半球不对称变暖的响应，使用了由两种不同的BBA排放(CMIP6默认和1990-2020年时间平滑)强迫的共同体地球系统模型第2版大集合的100个成员集合。这两个集合平均值之间的差异表明，海洋温度异常发生在BBA变率较高的时期，并随后持续数十年。在北大西洋，由于大西洋经向翻转环流的减缓，向北的海洋热量输送减少，从而有效地补偿了表面变暖。在北太平洋，异常的越赤道环流(CEC)减少了向北的海洋热量输送，从而抵消了表面变暖的影响。通过异常的CEC汇聚在南太平洋的热量被分流到次表层，并有助于形成持久的海洋温度异常。异常的CEC是通过狭窄的西部边界流和整个盆地的近地表Ekman输送与纬度相关的贡献来维持的。这些结果表明，强迫场的年际变化可能会在长时间尺度上显著改变背景气候状态，从而在没有年际变化的情况下强迫的CMIP6级气候预测存在潜在的不确定性。
Biomass burning aerosol (BBA) emissions in the Coupled Model Intercomparison Project phase 6 (CMIP6) historical forcing fields have enhanced temporal variability during the years 1997–2014 compared to earlier periods. Recent studies document that the corresponding inhomogeneous shortwave forcing over this period can cause changes in clouds, permafrost, and soil moisture, which contribute to a net terrestrial Northern Hemisphere warming relative to earlier periods. Here, we investigate the ocean response to the hemispherically asymmetric warming, using a 100-member ensemble of the Community Earth System Model version 2 Large Ensemble forced by two different BBA emissions (CMIP6 default and temporally smoothed over 1990–2020). Differences between the two subensemble means show that ocean temperature anomalies occur during periods of high BBA variability and subsequently persist over multiple decades. In the North Atlantic, surface warming is efficiently compensated for by decreased northward oceanic heat transport due to a slowdown of the Atlantic meridional overturning circulation. In the North Pacific, surface warming is compensated for by an anomalous cross-equatorial cell (CEC) that reduces northward oceanic heat transport. The heat that converges in the South Pacific through the anomalous CEC is shunted into the subsurface and contributes to formation of long-lasting ocean temperature anomalies. The anomalous CEC is maintained through latitude-dependent contributions from narrow western boundary currents and basinwide near-surface Ekman transport. These results indicate that interannual variability in forcing fields may significantly change the background climate state over long time scales, presenting a potential uncertainty in CMIP6-class climate projections forced without interannual variability.