Late-glacial and Holocene deglaciation chronology of the northeast Icelandic Ice Cap

冰岛靠近北极前缘，拥有冰盖，是研究过去和现代气候变化的战略可及自然实验室。与格陵兰岛一样，冰岛冰盖(IIS)为北大西洋提供淡水，并改变其温盐洋流的循环。尽管IIS边缘相对较好地受到海洋或沿海证据的限制，但人们对其陆上特征及其在全新世变暖期间的衰退速度知之甚少。这项研究旨在利用冰岛东北部的宇宙成因核素测年来填补第四纪晚期冰川消融期间内陆IIS的这一年代学空白。在Vatnajökull以北发现了冰盖越过边缘的陆地证据，如冰雹、冰川喷发和Kame阶地，在那里将使用两个互补和独立的宇宙成因暴露同位素(36Cl和3He)来确定IIS退缩的这些形态标志的日期。在这样做的过程中，我们将限制冰缘的年代学，并测试冰盖消融模型。宇宙成因抽样战略将包括互补的表面巨石和来自普通熔岩流并嵌入形态标记的混合鹅卵石的36Cl深度剖面。所有表面样品将分别由富钙斜长石和共生辉石斑晶的36Cl和3He表面暴露年龄确定。用~(36)Cl和~3He进行双重测年，并结合相关的深度剖面控制产生机制，将确保宇宙成因年龄是可靠的，并有效地提供IIS冰川消融的年龄限制。更好地理解IIS在已知快速气候变化期间的行为，将为IIS模型的校准提供新的结合点，并将使人们能够更好地评估陆地融水流向北大西洋的流量和时间。这项工作将有助于更好地了解北半球过去20ka以来的气候演变，并利用过去的类比更好地理解现代冰盖的演变。

Close to the Arctic front, Iceland with its ice sheet is a strategic accessible natural laboratory to study past and modern climate changes. Like in Greenland the Icelandic Ice Sheet (IIS) provides freshwater to the North Atlantic and modifies the circulation of its thermohaline currents. While the IIS margins are relatively well constrained offshore by marine or coastal evidences, little is known about its onshore characteristics and its rates of recession during the Holocene warmer periods. This study aims at filling this chronological gap of the IIS inland during the late Quaternary deglaciation using cosmogenic nuclides dating in northeast Iceland. Terrestrial evidences of the ice sheet past margins such as moraines, glacial outwash and kame terraces have been identified north of Vatnajökull where two complementary and independent cosmogenic exposure isotopes (36Cl and 3He) will be used to date these morphological markers of the IIS retreat. In doing so, we will constrain the chronology of the ice margins and test ice-sheet deglaciation models. The cosmogenic sampling strategy will consist of complementary surface boulders and 36Cl depth profiles of amalgamated cobbles originating from common lava flows and embedded in the morphological markers. All surface samples will be dated by both 36Cl and 3He surface exposure ages from Ca-rich plagioclases and from cogenetic pyroxene phenocrysts, respectively. The double dating with 36Cl and 3He and a control of the production mechanisms with the associated depth profiles will ensure that the cosmogenic ages are sound and effective in providing age constraints of the IIS deglaciation. Improved understanding of the IIS behaviour during periods of known rapid climate change will provide new tie-points for the calibration of the IIS models and will allow a better assessment of the volume and timing of terrestrial meltwater flux to the North Atlantic. This work will contribute to a better understanding of climate evolution in the North Hemisphere over the last 20 ka and, to a better understanding of the evolution of modern Ice sheets using analogue from the past.