Tropical Pacific temperature seasonality around Meltwater Pulse-1A from IODP Expedition 310 corals

季节性在地球气候中起着至关重要的作用，但过去地球表面温度的年度周期的演变没有受到很好的限制--特别是对热带海洋--全球气候动态的关键参与者。温度年周期的幅度被认为是受地球在更长时间尺度上的轨道变化所调制的。季节性对于通过回顾模拟过去的气候来改进对未来气候变化的模型预测具有相当重要的意义，但从地质档案中获得的关于温度年度循环的可量化证据很少。浅水珊瑚化石为热带海洋提供了独特但相对罕见的海洋表面温度季节性档案，并可通过U系列方法精确测定年代。来自大西洋的新出现的珊瑚研究表明，热带表层海洋的温度季节性主要受间冰期期间轨道日照变化的控制，即使在气候显著扰动和海平面突然上升的时期也是如此。然而，关于冰川和冰川消融的可比信息仍然缺乏。在这里，我们建议通过分析IODP探险310‘大溪地海平面’钻探的浅水珊瑚(Porite)化石骨架中的地球化学物，重建和量化最后一次冰川消融期间热带太平洋温度的季节性，特别关注熔化水脉冲(MWP)1A(约14.5KYR前)。此外，我们还打算测试热带太平洋温度季节性是否主要受以下期间的轨道日照变化控制：(1)最后一次冰川消退，特别是(2)MWP-1A期间，这段时间的特点是海平面突然上升、气候变化和气候剧烈扰动。我们的预期珊瑚结果将提供难得的替代数据，用于与最先进的气候模式模拟进行比较，例如德国气候建模倡议PALMOD的“从最后一次间冰期到人类世-模拟完整的冰川周期”的结果，并将有助于更好地理解热带太平洋气候变化对冰川-间冰期时间尺度突变扰动的季节性反应。这对于改进对未来热带太平洋气候变异性及其在与社会有关的时间尺度上的全球遥相关的预测具有重要意义。

Seasonality plays a fundamental role in Earth’s climate, but the evolution of the annual cycle of temperature at Earth’s surface is not well constrained in the past - in particular for the tropical ocean, a key player in global climate dynamics. The amplitude of the temperature annual cycle is thought to be modulated by Earth’s orbital variations on longer timescales. Seasonality is of considerable importance to improved model projections of future climate change through retrospective simulations of past climates, but quantifiable evidence of the annual cycle of temperature from geological archives is sparse. Fossil shallow-water corals provide a unique but relatively rare archive of sea surface temperature seasonality for the tropical ocean and can be precisely dated by the U-series method. Emerging coral work from the Atlantic suggests that temperature seasonality of the tropical surface ocean is controlled mainly by orbital insolation changes during interglacials, even during periods of substantial climate perturbations and abrupt sea-level rise. However, comparable information for glacials and deglaciations is still lacking. Here we suggest reconstructing and quantifying tropical Pacific temperature seasonality during the last deglaciation with a specific focus on meltwater pulse (MWP) 1A (~14.5 kyr ago), by analysing geochemical proxies in the skeletons of fossil shallow-water corals (Porites) drilled by IODP Expedition 310 ’Tahiti Sea Level’. Supplemented by a new collection of modern Tahiti Porites corals recovered from the vicinity of the Expedition 310 drill sites serving as present-day benchmark to robustly assess the uncertainties in our reconstructions, we intend to test the hypotheses if tropical Pacific temperature seasonality is controlled mainly by orbital insolation changes during (1) the last deglaciation and, in particular, (2) during MWP-1A, a period characterized by abrupt sea-level rise and climate change and substantial climate perturbations. Our anticipated coral results will provide rare proxy data for comparisons with state-of-the-art climate model simulations, e.g., those of the German Climate Modeling Initiative PALMOD "From the Last Interglacial to the Anthropocene – Modeling a Complete Glacial Cycle", and will contribute to an improved understanding of the seasonal response of tropical Pacific climate variability to abrupt perturbations on glacial-interglacial timescales. This is of high relevance for improved projections of future tropical Pacific climate variability and its global teleconnections on society-relevant timescales.