题型：阅读理解 题类：模拟题 难易度：普通
上海市嘉定区2020届高考英语一模试卷
A tiny clue found in ancient deposits has unlocked big secrets about Greenland's past and future climate. Just beyond the northwest edge of the vast Greenland Ice Sheet, researchers have discovered lake mud that have survived the last ice age. The mud, and remains of common flies in it, record two interglacial periods(间冰期)in northwest Greenland.
Although researchers have long known these two periods—the early Holocene and Last Interglacial—experienced warming in the Arctic, the mix of fly species shows that Greenland was even warmer than previously thought. "As far as we know, it has never been found in Greenland. We think this is the first time anyone has reported it in ancient deposits or modern lakes there," Axford said. "We were really surprised to see how far north it migrated (迁徙)."
This new information could help researchers better measure Greenland's sensitivity to warming, by testing and improving models of climate and ice sheet behaviour. Those models could then improve predictions of how Greenland's ice sheet might respond to man-made global warming. After all, Greenland covers 80 per cent of the Arctic country and holds enough ice to equal 20 feet of global sea level. "Northwest Greenland might feel really remote, but what happens to that ice sheet is going to matter to everyone in every coastal city around the world," said Yarrow Axford, an associate professor in the team. "One of the big uncertainties in climate science is how fast the Earth changes when it gets warmer. Geology gives us an opportunity to see what happened when the Earth was warmer than today," said Axford.
People might be surprised to see how today's Greenland looked during the last two interglacial periods. During the Last Interglacial, global sea levels increased by 15 to 30 feet, largely due to thinning of Greenland and Antarctica's ice sheets. However, now researchers believe northern Greenland's ice sheet experienced stronger warming than previously thought, which could mean that Greenland is more responsible for that sea-level rise.
Finding lake deposits older than about 10,000 years, however, has been historically very difficult in Greenland. To measure these ancient temperatures, researchers look to ice cores (冰核) and lake deposits. Since ice and lake deposits form by a gradual buildup on annual layers of snow or mud, these cores contain history of the past. By looking through the layers, researchers can obtain climate clues from centuries ago.
Nowadays airfare isn't getting any cheaper with fuel costs rising every day. Luckily, there are plenty of ways to find the most affordable fares and also avoid paying as many extra charges as possible when you plan ahead.
♦ Getting the best fare Fly during the least popular times. Tuesday, Wednesday and Saturday are the slowest days to fly, which means cheaper deals than the rest of the week. You can also find reduced rates on early morning flights, since many people don't like to get up before the sun to get to the airport. Earlier boarding times can also considerably cut down your chances of getting delayed because of other delayed flights or mechanical issues. Choose your seat later. Some airlines charge you to pick your seat when you book online, adding even more to the bottom line of your ticket cost. If you show up early on your travel day, you can still have a chance to get suitable seats that others are not willing to pay extra for ahead of time. Fly on holidays. You already know that summer is the most expensive time to fly, but the days surrounding holidays can also be crazy. Save big if you're willing to travel on major holidays, such as Thanksgiving and Christmas. Don't wait until the last-minute to book. Book too early or too late and you could end up paying more than you need to. The best time to book is between three months and six weeks from when you want to travel. ※ ※ ※ ※ ※ ※ ※ ※ ♦Avoiding extra fees Avoid the upgrade(升级). It's not necessary. Sometimes upgrades are free, but mostly you will be charged for seeking a last-minute bump to first class, and the cost can be very high. Fly carry-on only. Baggage fees vary wildly, but almost all airlines charge them and charge big. It's easy to reduce the amount of stuff if you pack less clothes and only travel-sized toiletries. Planning to do a bit of laundry on your trip will also do. Pack your own snacks. Unless you're flying internationally, it's rare your flight comes with a free meal. So put some of your own snacks — homemade muffins, fruit and granola bars all make fantastic travel foods — into your bag and eat a lot better, and cheaper, than other passengers. |
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