Fjords are recognized as hotspots of organic carbon (OC) burial in the coastal ocean. In fjords with glaciated catchments, glacier discharge carries large amounts of suspended matter. This sedimentary load includes OC from bedrock and terrigenous sources (modern vegetation, peat, soil deposits), which is either buried in the fjord or remineralized during export, acting as a potential source of CO₂ to the atmosphere. In sub-Antarctic South Georgia, fjord-terminating glaciers have been retreating during the past decades, likely as a response to changing climate conditions. We determine sources of OC in surface sediments of Cumberland Bay, South Georgia, using lipid biomarkers and the bulk ¹⁴C isotopic composition, and quantify OC burial at present and for the time period of documented glacier retreat (between 1958 and 2017). Petrogenic OC is the dominant type of OC in proximity to the present-day calving fronts (60.4 ± 1.4% to 73.8 ± 2.6%) and decreases to 14.0 ± 2.7% outside the fjord, indicating that petrogenic OC is effectively buried in the fjord. Beside of marine OC, terrigenous OC comprises 2.7 ± 0.5% to 7.9 ± 5.9% and is mostly derived from modern plants and Holocene peat and soil deposits that are eroded along the flanks of the fjord, rather than released by the retreating fjord glaciers. We estimate that the retreat of tidewater glaciers between 1958 and 2017 led to an increase in petrogenic carbon accumulation of 22% in Cumberland West Bay and 6.5% in Cumberland East Bay, suggesting that successive glacier retreat does not only release petrogenic OC into the fjord, but also increases the capacity of OC burial.

中文翻译：

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由于近期冰川退缩，亚南极峡湾沉积物中的岩石和生物圈有机碳埋藏增加

峡湾被认为是沿海海洋中有机碳 (OC) 埋藏的热点。在有冰川集水区的峡湾中，冰川排放会携带大量悬浮物。这种沉积负荷包括来自基岩和陆源（现代植被、泥炭、土壤沉积物）的 OC，它们要么埋藏在峡湾中，要么在出口过程中再矿化，成为大气CO ₂的潜在来源。在亚南极地区的南乔治亚岛，在过去的几十年里，终止于峡湾的冰川一直在消退，这可能是对不断变化的气候条件的回应。我们使用脂质生物标志物和大量¹⁴C 同位素组成，并量化目前和记录的冰川退缩时期（1958 年至 2017 年）的 OC 埋藏。岩源 OC 是当今产犊锋附近的主要 OC 类型（60.4 ± 1.4% 至 73.8 ± 2.6%），并在峡湾外减少至 14.0 ± 2.7%，表明岩源 OC 有效地埋藏在峡湾中。除海洋 OC 外，陆源 OC 占 2.7 ± 0.5% 至 7.9 ± 5.9%，主要来自现代植物和全新世泥炭和沿峡湾侧翼侵蚀的泥炭和土壤沉积物，而不是由后退的峡湾冰川释放。我们估计 1958 年至 2017 年间潮水冰川的退缩导致坎伯兰西湾和坎伯兰东湾的岩源碳积累增加了 22% 和 6.5%，