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Marine geophysical and geological investigations of past flow and stability of a major Greenland ice stream in the Late Quaternary

对格陵兰岛晚第四纪主要冰流过去流动和稳定性的海洋地球物理和地质调查

基本信息

批准号：
NE/D001951/1
负责人：
Colm O'Cofaigh
金额：
$ 32.78万
依托单位：
Durham University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2007
资助国家：
英国
起止时间：
2007 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FD001951%2F1
关键词：
Marine geophysical geological investigations past

项目摘要

Recent observations from around the Greenland Ice Sheet have shown that the fast flowing glaciers - 'ice streams' - which drain the ice sheet into the sea are thinning, speeding up and in some cases their floating margins are disintegrating. It is unknown if this is part of a natural cycle or if it is a response to human-induced climate change. The ice streams are important because they are responsible for most of ice discharged from the Greenland Ice Sheet today and would have played a similar important role in the past. If ice-stream velocities increase, more ice will be delivered to the oceans around Greenland, and as a consequence global sea level will rise. Ice streams are the main mechanism by which icebergs and meltwater are delivered to the ocean. They therefore affect ocean circulation and climate. Computer simulations of the effects of melting of the Greenland Ice Sheet on the North Atlantic have shown that the freshwater runoff produced by this melting could seriously weaken or even stop the thermohaline circulation which is ultimately responsible for the relatively mild climate of much of western Europe. It is therefore important to understand if these changes to the Greenland Ice Sheet are unique to the present day or if similar changes have occurred to Greenland ice streams in the 'recent' geological past of the Late Quaternary (last 50,000 years or so) i.e., prior to any possible human-influence on climate. It is also important to understand what controls the fast flow of such ice streams and what might cause them to speed up or slow down. In this project we propose to address the question of the past behaviour of one of the major ice streams to drain the modern Greenland Ice Sheet: Jakobshavns Isbrae in central west Greenland. Jakobshavns Isbrae is the fastest ice stream in the Greenland Ice Sheet today. It flows at several kilometres per year and accounts for about 7% of the total ice drained from the ice sheet. It therefore exerts a major influence on the ice sheet today and would likely have had a similar influence in the past. Our overall scientific goal in this project is to reconstruct the behaviour of Jakobshavns Isbrae during the Late Quaternary period and particularly since about 20,000 years before present. We will collect marine geophysical data and cores of sea-bed sediments from offshore of Jakobshavns Isbrae in order to answer questions regarding how long this ice stream has been in existence; what were it's dimensions during past glaciations; when and how rapidly did it last retreat from the continental shelf of Greenland; what are the processes responsible for the high flow velocities of this ice stream and what are the major controls on it's location; what is the nature of sedimentation associated with Jakobshavns Isbrae; and has it undergone large-scale collapse prior to modern times. The results from this project will significantly advance scientific understanding in the following areas: (1) The behaviour of Jakobshavns Isbrae - a major ice stream of the Greenland Ice Sheet / in the recent geological past (last 50,000 years) and its role in the evolution of the ice sheet as a whole during this period. In particular if Jakobshavns Isbrae has experienced past episodes of large-scale disintegration analogous to those occurring around Greenland today; (2) The mechanisms by which ice streams flow fast; (3) The factors that cause ice streams to form and to stop; (4) The nature of sediments beneath ice streams and the relationship of these sediments to the high velocities of ice streams. These results will be highly relevant to workers in the related fields of glaciology, oceanography, and climate modelling.

最近对格陵兰冰盖周围的观测表明，将冰盖排入大海的快速流动的冰川（“冰流”）正在变薄、加速，在某些情况下，其浮动边缘正在崩解。目前尚不清楚这是否是自然循环的一部分，或者是否是对人类引起的气候变化的反应。冰流很重要，因为它们是当今格陵兰冰盖排出的大部分冰的来源，并且在过去也发挥着类似的重要作用。如果冰流速度增加，更多的冰将被输送到格陵兰岛周围的海洋，从而导致全球海平面上升。冰流是将冰山和融水输送到海洋的主要机制。因此，它们影响海洋环流和气候。格陵兰冰盖融化对北大西洋影响的计算机模拟表明，融化产生的淡水径流可能会严重削弱甚至停止温盐环流，而温盐环流最终导致西欧大部分地区相对温和的气候。因此，重要的是要了解格陵兰冰盖的这些变化是否是当今特有的，或者格陵兰冰流是否在晚第四纪的“最近”地质过去（过去 5 万年左右）（即在人类对气候产生任何可能影响之前）发生过类似的变化。了解是什么控制着此类冰流的快速流动以及什么可能导致它们加速或减慢也很重要。在这个项目中，我们建议解决现代格陵兰冰盖的主要冰流之一：格陵兰岛中西部的雅各布港伊斯布雷（Jakobshavns Isbrae）过去行为的问题。雅各布港伊斯布雷是当今格陵兰冰盖上最快的冰流。它每年以数公里的速度流动，约占冰盖流失冰总量的7%。因此，它对今天的冰盖产生了重大影响，并且在过去也可能产生类似的影响。我们在该项目中的总体科学目标是重建雅各布港在第四纪晚期，特别是距今约 20,000 年前的行为。我们将从雅各布港近海收集海洋地球物理数据和海底沉积物核心，以回答有关这条冰流存在了多久的问题；过去冰川时期它的尺寸是多少？它上次从格陵兰大陆架撤退的时间和速度有多快；造成该冰流高流速的过程是什么？对其位置的主要控制因素是什么？与 Jakobshavns Isbrae 相关的沉积的性质是什么？并在现代之前经历过大规模的崩溃。该项目的结果将显着推进以下领域的科学认识：(1) 雅各布港 - 格陵兰冰盖的主要冰流 - 在最近的地质历史（过去 5 万年）中的行为及其在这一时期整个冰盖演化中的作用。特别是如果雅各布港曾经经历过类似于今天格陵兰周围发生的大规模解体事件； (2)冰流快速流动的机制；（三）引起冰流形成和停止的因素； (4)冰流下方沉积物的性质以及这些沉积物与冰流高速的关系。这些结果将与冰川学、海洋学和气候建模相关领域的工作者高度相关。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Baffin Bay paleoenvironments in the LGM and HS1: Resolving the ice-shelf question

DOI：
10.1016/j.margeo.2017.09.002
发表时间：
2017-09
期刊：
Marine Geology
影响因子：
2.9
作者：
Marine Geology Elsevier;A. Jennings;J. Andrews;C. Ó. Cofaigh;G. St‐Onge;S. Belt;Patricia Cabedo-Sanz;C. Pearce;C. Hillaire‐Marcel;D. C. Campbell
通讯作者：
Marine Geology Elsevier;A. Jennings;J. Andrews;C. Ó. Cofaigh;G. St‐Onge;S. Belt;Patricia Cabedo-Sanz;C. Pearce;C. Hillaire‐Marcel;D. C. Campbell

Submarine landforms reveal varying rates and styles of deglaciation in North-West Greenland fjords

海底地貌揭示了格陵兰岛西北部峡湾不同的冰川消融速度和类型