The number of sedimentary records collected along the Brazilian continental margin has increased significantly in recent years, but relatively few are located in shallow waters and register paleoceanographic processes in the outer shelf–middle slope prior to 10–15 ka. For instance, the northward flow up to 23–24^∘ S of cold and fresh shelf waters sourced from the Subantarctic region is an important feature of current hydrodynamics in the subtropical western South Atlantic Ocean, and yet limited information is available for the long-term changes of this system. Herein, we considered a suite of organic and inorganic proxies – alkenones-derived sea surface temperature (SST), δD-alkenones, δ¹⁸O of planktonic foraminifera, and ice-volume free seawater δ¹⁸O_IVF−SW – in sediment from two cores (RJ-1501 and RJ-1502) collected off the Rio de Janeiro Shelf (SE Brazilian continental shelf) to shed light on SST patterns and relative salinity variations since the end of the last glacial cycle in the region and the implications of these processes over a broader spatial scale. The data indicate that, despite the proximity (∼40 km apart) of both cores, apparently contradictory climatic evolution occurred at the two sites, with the shallower (deeper) core RJ-1501 (RJ-1502) showing consistently cold (warm) and fresh (salt) conditions toward the Last Glacial Maximum (LGM) and last deglaciation. This can be reconciled by considering that the RJ-1501 core registered a signal from mid- to high latitudes on the upper slope off Rio de Janeiro represented by the influence of the cold and fresh waters composed of Subantarctic Shelf Water and La Plata Plume Water transported northward by the Brazilian Coastal Current (BCC). The data from core RJ-1502 and previous information for deep-cores from the same region support this interpretation. In addition, alkenone-derived SST and δ¹⁸O_IVF−SW suggest a steep thermal and density gradient formed between the BCC and Brazil Current (BC) during the last climate transition which, in turn, may have generated perturbations in the air–sea heat flux with consequences for the regional climate of SE South America. In a scenario of future weakening of the Atlantic Meridional Overturning Circulation, the reconstructed gradient may become a prominent feature of the region.

中文翻译：

---

南大西洋西部上部和下部大陆斜坡之间的晚冰期古海洋演化对比

近年来，沿巴西大陆边缘收集的沉积记录数量显着增加，但位于浅水区的沉积记录相对较少，并且在外陆架（中坡在10到15之前）记录了古海洋学过程。 ？？K a。例如，北向流量最大为23“24†^??? 来自亚南极地区的冷淡水和架子水是南亚热带西部大西洋目前水动力的重要特征，但对于该系统的长期变化而言，信息有限。在这里，我们考虑了一整套有机和无机代理– 烯酮衍生的海平面温度（SST）， I' d -alkenones，I' ¹⁸ ö的浮游有孔虫，并在冰冷体积自由海水I' ¹⁸ ö _{IVFâ???? SW} â???? 来自里约热内卢大陆架（巴西东南部大陆架）的两个岩心（RJ-1501和RJ-1502）的沉积物揭示了自该地区最后一次冰川循环结束以来的SST模式和相对盐度变化。这些过程在更广泛的空间尺度上的意义。数据表明，尽管接近（≥40两个岩心之间相距公里？，两个站点发生了明显矛盾的气候演变，其中较浅（较深）的岩心RJ-1501（RJ-1502）始终朝着寒冷（温暖）和新鲜（盐分）的方向发展最后冰河最大值（LGM）和最后冰消。可以通过考虑RJ-1501芯在里约热内卢上坡的中高纬度处记录到一个信号来进行调和，该信号由亚南极陆架水和La Plata羽水组成的冷淡水的影响来表示巴西沿海海流（BCC）向北。来自核心RJ-1502的数据和来自同一地区的深层核心的先前信息支持这种解释。此外，烯酮衍生SST和I' ¹⁸ ö _{IVFâ???? SW}表明在最后一次气候转变期间，BCC和巴西洋流（BC）之间形成了陡峭的热和密度梯度，这反过来可能在空气中产生了扰动–海热通量，对东南SE的区域气候产生了影响美国。在未来大西洋子午线翻转环流减弱的情况下，重建的梯度可能会成为该地区的突出特征。