Past circulation along the western Iberian margin

Fifteen Iberian margin sediment cores, distributed between 43°12'N and 35°53'N, have been used to reconstruct spatial and temporal (sub)surface circulation along the Iberian margin since the Last Glacial period. Time-slice maps of planktonic foraminiferal derived summer sea surface temperature (SST) and export productivity (Pexp) were established for specific time intervals within the last 35 ky: the Holocene (Recent and last 8 ky), Younger Dryas (YD), Heinrich Stadials (HS) 1, 2a, 2b, 3, and the Last Glacial Maximum (LGM). The SST during the Holocene shows the same latitudinal gradient along the western Iberian margin as present-day with cold but productive areas that reflect the influence of coastal upwelling centers. The LGM appears as a slightly less warm, but more productive period relative to the Holocene and present-day conditions, suggesting that sea-level minima forced a westward displacement of the coastal upwelling centers possibly accompanied by a strengthening of northward winds. During the YD, a longitudinal thermal front is depicted at 10°W, with cold polar waters offshore and warmer subtropical waters inshore, suggesting that the subtropical Paleo-Iberian Poleward Current more likely flowed at a more inshore location masking the local SST signal and amplitude of variation. A substantial cooling and drop in productivity is observed during all HS, in particular HS1 and HS3, reflecting the penetration of icebergs-derived meltwater. These most extreme southward extensions of very cold waters define a strong SST gradient that marks a possible Paleo-Azores Front. Higher production south of this front was likely fed by frontal nutrient advection.本数据集采用分布于北纬43°12′至35°53′之间的15个伊比利亚陆缘沉积物岩芯，重建了末次冰期以来伊比利亚陆缘表层及次表层环流的时空分布特征。基于浮游有孔虫壳体信息，我们构建了过去35千年内特定时段的夏季海表温度（Sea Surface Temperature, SST）与输出生产力（Export Productivity, Pexp）的时间切片分布图，涵盖时段包括全新世（现代及过去8千年）、新仙女木期（Younger Dryas, YD）、海因里希冷期（Heinrich Stadials, HS）1、2a、2b、3，以及末次盛冰期（Last Glacial Maximum, LGM）。全新世时期的海表温度与现今一致，沿伊比利亚西部陆缘呈现清晰的纬向梯度，沿岸分布着低温但高生产力的区域，这反映了沿岸上升流中心的影响。相较于全新世及现代环境，末次盛冰期的海表温度略低，但生产力更高，这表明当时的海平面低位期迫使沿岸上升流中心向西迁移，可能伴随北向风力的增强。新仙女木期期间，在西经10°处出现一条纬向热锋：离岸区域为寒冷的极地水团，近岸区域则为温暖的亚热带水团，这暗示古伊比利亚极向流更可能位于近岸区域，掩盖了当地的海表温度信号及其变化幅度。所有海因里希冷期均出现显著降温与生产力下降，尤以HS1和HS3最为明显，这反映了冰山融水的侵入。这些极端南下的冷水团形成了强烈的海表温度梯度，标志着一处可能存在的古亚速尔锋面。该锋面以南区域的更高生产力，大概率得益于锋面带来的营养盐平流补给。