File:Sea Ice and Icebergs off East Antarctica.jpg
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Summary
DescriptionSea Ice and Icebergs off East Antarctica.jpg |
English: Image of a variety of ice types off the coast of East Antarctica.
Brilliant white ice fills the right half of this image. It is fast ice, and derives its name from the fact that it holds fast to the shore. This ice is thick enough to completely hide the underlying seawater, hence its brilliant white colour. Trapped within the fast ice, and stuck along the edge of it, are icebergs. Icebergs form by calving off ice shelves—thick slabs of ice attached to the coast. Ice shelves can range in thickness from tens to hundreds of meters, and the icebergs that calve off of them can tower over nearby sea ice. One iceberg, drenched with meltwater, has toppled and shattered (image upper right). The water-saturated ice leaves a blue tinge. The icebergs along the edge of the fast ice are likely grounded on the shallow sea floor, and their presence may help hold the fast ice in place. Farther out to sea is pack ice that drifts with winds and currents. Much thinner than the fast ice, the translucent pack ice appears in shades of blue-gray. The pack ice includes some newly formed sea ice. As seawater starts to freeze, it forms tiny crystals known as frazil (image center). Although the individual crystals are only millimeters across, enough of them assembled together are visible from space. Constantly moved by ocean currents, frazil often appears in delicate swirls. Frazil crystals can coalesce into thin sheets of ice known as nilas (image top). Sheets of nilas often slide over each other, eventually merging into thicker layers of ice. Français : La glace blanche et unie à droite de l'image est celle de la banquise côtière (ce nom tire son origine du fait qu'elle tient bien sur le rivage) Elle est assez épaisse pour toujours complètement masquer la mer sous jacente. Des icebergs sont ici piégés (probablement échoué sur le fond) contre la banquise côtière et collés à sa périphérie (Leur présence peut aider à maintenir la banquise côtière en place). ils se forment en vêlant à partir des glaciers et plateaux de glace (grandes dalles de glace fixées à la côte). L'épaisseur des plates-formes de glace variee de quelques dizaines à plusieurs centaines de mètres, et les icebergs qui en vêlent peuvent dominer la banquise. En haut à droite un iceberg imbibé d'eau de fonte, s'est renversé et s'est brisé (image en haut à droite). La glace saturée d'eau est bleutée.
Plus loin en mer se trouve une banquise libre qui dérive avec les vents et les courants : Bien plus fine que la banquise côtière, elle est translucide et apparaît dans des tons de bleu-gris. Elle inclue de la "glace de mer" nouvellement formée. Quand la mer commence à geler, elle forme de minuscules cristaux dits frazil (au centre de l'image). Bien que les cristaux individuels ne mesurent que quelques millimètres, un nombre suffisant de cristaux assemblés sont visibles de l’espace. Constamment déplacé par les courants océaniques, le frasil apparaît souvent sous forme de tourbillons délicats. Les cristaux de frasil peuvent former une fine couche de glace appelée nilas (image du haut). Des nappes de nilas glissent souvent les unes sur les autres, pour finalement se fondre en couches de glace plus épaisses |
Date | |
Source | NASA Earth Observatory |
Author | Jesse Allen and Robert Simmon |
Image captured by the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite. EO-1 ALI data provided courtesy of the NASA EO-1 team.
Licensing
Public domainPublic domainfalsefalse |
This file is in the public domain in the United States because it was solely created by NASA. NASA copyright policy states that "NASA material is not protected by copyright unless noted". (See Template:PD-USGov, NASA copyright policy page or JPL Image Use Policy.) | ||
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Items portrayed in this file
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7 October 2011
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Date/Time | Dimensions | User | Comment | |
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current | 02:46, 24 October 2011 | 1,954 × 4,800 (2.46 MB) | Originalwana | {{Information |Description ={{en|1=Image of a variety of ice types off the coast of East Antarctica. Brilliant white ice fills the right half of this image. It is fast ice, and derives its name from the fact that it holds fast to the shore. Th |
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Metadata
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Image title |
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Width | 6,841 px |
Height | 10,771 px |
Bits per component |
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Compression scheme | LZW |
Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 100 dpi |
Vertical resolution | 100 dpi |
Data arrangement | chunky format |
Software used | Adobe Photoshop CS5 Macintosh |
File change date and time | 15:59, 20 October 2011 |
Color space | Uncalibrated |
Date and time of digitizing | 07:25, 12 October 2011 |
Date metadata was last modified | 11:59, 20 October 2011 |
Unique ID of original document | xmp.did:0A801174072068119457CFC56BBA7858 |