美国麻省理工学院ranganathan meghana研究组取得一项新突破。他们报道了天然冰川的一种修正粘性流动规律——从实验室到冰原的尺度变换。该项成果发表在2024年5月30日出版的《美国科学院院刊》上。
据介绍,冰川流动调节着海平面,并在很大程度上受冰的粘滞变形的控制。多种分子尺度的机制促进粘质变形,但目前尚不清楚每种机制如何促进冰川尺度的变形。
研究团队提出了一个冰变形模型,该模型连接了实验室和冰川尺度,统一了现有的粘滞参数估计,提供了一个框架用于估计观测参数,并将实验室观测得出的流动规律纳入冰川流动模型。
他们的结果产生了南极冰盖主要变形机制的地图,显示出与长期存在的假设相反,以应力指数n=4为特征的位错蠕变可能在所有快速流动区域占主导地位。从n=3的标准值开始的这种增加极大地改变了气候条件,在这种条件下,海洋冰盖可能变得不稳定,并推动海平面快速上升。
附:英文原文
title: a modified viscous flow law for natural glacier ice: scaling from laboratories to ice sheets
author: ranganathan, meghana, minchew, brent
issue&volume: 2024-5-30
abstract: glacier flow modulates sea level and is governed largely by the viscous deformation of ice. multiple molecular-scale mechanisms facilitate viscous deformation, but it remains unclear how each contributes to glacier-scale deformation. here, we present a model of ice deformation that bridges laboratory and glacier scales, unifies existing estimates of the viscous parameters, and provides a framework for estimating the parameters from observations and incorporating flow laws derived from laboratory observations into glacier-flow models. our results yield a map of the dominant deformation mechanisms in the antarctic ice sheet, showing that, contrary to long-standing assumptions, dislocation creep, characterized by a value of the stress exponent n=4, likely dominates in all fast-flowing areas. this increase from the canonical value of n=3 dramatically alters the climate conditions under which marine ice sheets may become unstable and drive rapid rates of sea-level rise.
doi: 10.1073/pnas.2309788121
source:
来源:科学网 小柯机器人