萎缩的冰川为格陵兰的冰盖创造了新常态
随着格陵兰冰川的退缩,它们正在以越来越快的速度流失冰块。
米卡莉亚·金(Michalea King), CC BY-ND

格陵兰岛是地球上最大的岛屿,大约80%的岛屿都被格陵兰岛覆盖 巨大的冰。 Slowly flowing glaciers connect this massive frozen reservoir of fresh water to the ocean, but because of climate change, these glaciers are rapidly retreating.缓慢流动的冰川将这个庞大的冰冻淡水库连接到海洋,但是由于气候变化,这些冰川正在迅速退缩。

我是地球科学家 who studies how changes to Greenland's glaciers affect the stability of the ice sheet as a whole.他研究了格陵兰冰川的变化如何影响整个冰盖的稳定性。 Healthy glaciers are stable in size and shape and act as drains for the ice sheet, transporting ice into the sea.健康的冰川尺寸和形状稳定,可作为冰盖的排水管,将冰运入海中。 They maintain a balance where the ice added each year roughly equals the ice lost to the sea.他们保持着平衡,每年增加的冰量等于流向大海的冰量。

但是由于气候变化引起的变暖,这种变化已经改变。

For years, scientists have watched as glaciers around the world retreat.多年以来,科学家一直看着世界各地的冰川消退。 But our research has found that the glaciers along the edge of Greenland have retreated so much that they no longer但是我们的研究发现,格陵兰岛边缘的冰川已经退缩了很多,以至于不再 使喂养它们的冰盖保持平衡.


内在自我订阅图形


As the glaciers retreat up valleys, they flow faster and bring more ice from inland to the sea.随着冰川退缩到山谷中,它们的流动速度更快,并将更多的冰从内陆带到海洋。 Imagine a traffic jam: When a highway is jampacked with cars – or ice – it flows slowly.想象一下交通拥堵:当高速公路上挤满了汽车或冰块时,它会缓慢流动。 But as the jam or glacier gets smaller, the number of cars, or the amount of ice, that can flow by in a given time increases.但是,随着果酱或冰川的变小,在给定时间内可以流过的汽车数量或冰量会增加。

Greenland's ice sheet is now out of balance.格陵兰的冰盖现在失衡了。 The new normal is an新常态是 年总冰量损失.

The place where glaciers meet the sea – called the calving front – is important for the stability of the entire ice sheet.冰川与海汇合的地方-产犊前线-对于整个冰盖的稳定性至关重要。 Jakobshavn Glacier has been retreating for decades.雅各布港冰川已经退缩了数十年。The place where glaciers meet the sea – called the calving front – is important for the stability of the entire ice sheet.冰川与海汇合的地方-产犊前线-对于整个冰盖的稳定性至关重要。 Jakobshavn Glacier has been retreating for decades.雅各布港冰川已经退缩了数十年。 米卡莉亚·金(Michalea King), CC BY-ND

边缘的变化,对整体的影响

Ice sheets are formed when snowfall accumulates over thousands of years and compresses into layers upon layers of ice.当降雪累积了数千年并形成层层冰盖时,就会形成冰盖。 But ice is not a perfectly rigid material – it behaves kind of like an但是冰不是一种完全刚性的材料,它的行为有点像 特浓又脆的蜂蜜.

Once an ice sheet becomes tall enough, the ice begins to flow outward because of its own weight.一旦冰盖变得足够高,冰由于其自身的重量而开始向外流动。 This ice is funneled down valleys toward the ocean, forming fast–flowing outlet glaciers.这些冰沿着山谷向下流向海洋,形成快速流动的出口冰川。 These glaciers can move as much as这些冰川可以移动多达 10英里 每年。

Although glaciers comprise only a narrow region at the edge of the ice sheet, they play a huge role in controlling how rapidly ice is drained from the sheet into the ocean.尽管冰川在冰盖边缘仅包含一个狭窄的区域,但它们在控制冰从冰盖排放到海洋的速度方面起着巨大的作用。 Generally, a glacier that extends a long distance through a valley通常,冰川延伸穿过山谷很长一段距离 会移动得更慢 并从冰盖中排出的冰要少于较短的冰。

Most of Greenland's glaciers end at the sea, where ocean water melts and weakens the ice until it breaks off in pieces that dramatically fall into the North Atlantic.格陵兰岛的大部分冰川终止于大海,海水融化并削弱了冰层,直到其破裂成碎片,并迅速落入北大西洋。 If ice is lost at the front of the glacier faster than it is replenished by upstream ice, the glacier will recede inland.如果冰川上游的冰块流失的速度比上游冰块补充冰块的速度快,那么冰川将向内陆退缩。 This is called glacial retreat.这就是所谓的冰川退缩。

撤退不仅缩短了冰川的长度,而且减少了 冰与周围山谷之间的摩擦。 With less surface area of ice touching the ground, the ice can flow faster.由于较少的冰表面积接触地面,因此冰可以更快地流动。 Much like a shrinking traffic jam, sustained glacier retreat results in faster-flowing glaciers that就像不断减少的交通拥堵一样,持续的冰川退缩导致冰川流动速度加快, 更快地将冰块排干.

The blue line shows the current boundary between the Jakobshavn Glacier (right side, light gray) and the floating ice (center, white) between the valley walls (top and bottom, dark gray).蓝线显示了Jakobshavn冰川(右侧,浅灰色)与山谷壁之间的浮冰(顶部,底部,深灰色)之间的当前边界。 The other colored lines show where this boundary was in previous years.其他彩色线显示了该边界在前几年的位置。The blue line shows the current boundary between the Jakobshavn Glacier (right side, light gray) and the floating ice (center, white) between the valley walls (top and bottom, dark gray).蓝线显示了Jakobshavn冰川(右侧,浅灰色)与山谷壁之间的浮冰(顶部,底部,深灰色)之间的当前边界。 The other colored lines show where this boundary was in previous years.其他彩色线显示了该边界在前几年的位置。 米卡莉亚·金(Michalea King), CC BY-ND

持续的亏损状态

Ocean and air temperatures have strong effects on glaciers.海洋和气温对冰川有强烈影响。 Both都 海洋气温 正在崛起。

For Greenland's glaciers, the warming ocean is the biggest cause of glacial retreat.对于格陵兰岛的冰川而言,变暖的海洋是造成冰川退缩的最大原因。 On average the glaciers have retreated about平均而言,冰川退缩了 自3年代中期以来1980公里,大部分撤退发生在2000年至2005年之间。

My colleagues and I used thousands of satellite images to measure changes in length, thickness and flow speed of Greenland's glaciers.我和我的同事们使用了数千个卫星图像来测量格陵兰冰川的长度,厚度和流速的变化。 With this information, we found two important things: Glacial retreat is accelerating, and the ice sheet is losing an astonishing – and also increasing – amount of ice each year.有了这些信息,我们发现了两件重要的事情:冰川退缩正在加速,冰盖每年都在失去惊人的冰量,而且还在增加。

我们的小组发现,今天,冰川流失了 每年从冰盖上多出14%的冰 –大约500亿吨–比1985年至1999年的平均水平要多。这种更快的流动导致覆盖格陵兰大部分地区的冰原收缩,但也改变了整个系统的动力。

The ice sheet is now in a new, unbalanced state of persistent mass loss.现在,冰盖处于持续失重的新的不平衡状态。 Before the year 2000, ice loss roughly equaled the ice added from snowfall, so the ice sheet was stable.在XNUMX年之前,冰的损失大致等于降雪增加的冰量,因此冰盖是稳定的。 Now, ice mass losses consistently exceed mass gains – even in the coolest years of relatively high snow accumulation.现在,即使在相对高积雪的最凉爽的年份,冰块的损失也始终超过质量的增加。 The glaciers used to act as an important traffic jam, keeping ice loss in check.过去,冰川起着重要的交通堵塞的作用,可控制冰块的流失。 Now, however, traffic flows more freely and the ice is able to more easily flow away from the ice sheet.然而,现在,交通更加自由地流动,并且冰能够更容易地从冰盖流走。

不幸的是,气温升高 表面融化增加,导致格陵兰岛目前积雪减少。 Given all these factors, my colleagues and I now estimate that the ice sheet may see a mass gain year考虑到所有这些因素,我和我的同事现在估计冰盖可能会出现质量增长的一年。 一个世纪只有一次.

有严重的麻烦,但尚未注定

Our study showed how widespread retreat drove both an increase in glacier discharge and a shift to persistent ice sheet mass loss.我们的研究表明,大范围的撤退既推动了冰川排放的增加,又使冰盖持续失去质量。 But this doesn't mean the ice sheet is doomed.但这并不意味着冰盖注定要失败。 Continued retreat and further increases in discharge are limited by topography.地形继续限制了撤退和排放量的进一步增加。

在接下来的几个世纪中,冰川可能会撤退到更高的地面上,并最终形成一个完整的 内陆冰盖,流量最小 –格陵兰岛上的冰块基本上很大,没有冰川可以将其排出。 Under this future scenario, the balance of the ice sheet would be determined only by surface changes – snow accumulation and surface melt.在这种未来情况下,冰盖的平衡将仅由表面变化(积雪和表面融化)决定。 This loss of ice would equal冰的损失等于 海平面上升米.

At this point, the fate of the ice sheet simply depends on whether it is melting faster than it grows from snowfall.此时,冰盖的命运仅取决于冰盖融化的速度是否快于降雪的速度。 In a warm world where climate change is not addressed, the ice sheet will slowly melt and ultimately disappear.在一个无法解决气候变化的温暖世界中,冰盖将缓慢融化并最终消失。 But if climate change is controlled and cooler temperatures are maintained for a prolonged period, it is possible that the Greenland ice sheet could regrow.但是,如果控制气候变化并长时间保持较凉的温度,格陵兰岛的冰盖可能会重新生长。 That day may be hundreds of years into the future, but it is actions made today that will decide the fate of Greenland's ice sheet.那天可能是未来数百年,但今天采取的行动将决定格陵兰冰原的命运。谈话

关于作者

博士后气候科学研究员Michalea King 美国俄亥俄州立大学

本文重新发表 谈话 根据知识共享许可。 阅读 原创文章.

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