>> the ocean beneath is probably the least accessible part of the world ocean. and just getting access to that is a triumph frankly as far as we are concerned. the ice shelf extends from the glacier and floats on the ocean. they believe it acts like a dam, holding back ice from sliding into the sea. if it goes away, sea levels go up. is there a sense of urgency in the work that you are doing? >> the sea level rises, the big question we are trying to get at. and peterman glacier, this experiment here, gives us an opportunity to get at the processes, and try to understand the basic physics to how that can happen. >> our visit to the ice camp was cut short. our pilots warned of something, ice fog moving in. and could strand us here for days. we high tailed it back to the helicopter. heading to another outpost of the expedition. what the scientists call boulder camp. set up on the edge of peterman glacier.

have been here for weeks gathering samples from rocks. >> this was probably deposited when the ice was maybe a few hundred to few thousand feet thicker. when deposited you are probably talking about, 600 feet of ice above us. >> above where we are now. >> above where we are now. peterman would have been much larger, dropping the rocks all over the surface. >> to the person at home who is looking at you guys chipping at rocks why should i care about this? >> we know if you warm the planet up. glaciers respond. they melt. the question is at what rate? how fast is that going to that pen? where is if the going to happen? where are the vulnerable spots in the ice sheet. to understand all that you have to understand how the ice sheet, what controls an ice sheet. we need to understand this glacier to provide a better prediction for the ice sheet. that matters to us because of sea level. if the glaciers can respond die namingly, we should all be concerned. because the that can create dynamic changes in sea level and flood infrastructure. we need new know that planning

>> reporter: we camped out next to the scientists. with 24 hours of light. we slept in the tents under the midnight sun. in the morning, we were shuttled out to meet the swedish ice breaker making its way around peterman glacier. it supports the scientists on land and acts as a floating laboratory. named after a norse god who sought wisdom. it is home to 50 climate scientists from around the world with similar convictions. their work is funded mostly by the swedish government. and the u.s. national science foundation. larry mayor, is one of geologists on the ship. and using sonar to map the ocean

creating the first detailed maps that show how peterman glacier slid into the sea. see it like skid marks of a car at an accident scene. >> yeah, the ice went here. the ice went there. we can see it. oh, stopped here. >> reporter: how much of the world's oceans have been mapped with detail. >> 6%, 7%. >> reporter: you can make the trip to peterman glacier a few weeks each summer when the ice melts enough to allow passage. >> see the blocks of ice drifting by. >> reporter: allen mix is running the ship's coring operation. trying to grab sediment from the sea floor. >> actually the coring site is under the block of ice. we just can't get there. we are trying to drift with the ice and sort of snook up on it. gently. >> reporter: it is hard to sneak up on anything in an ice breaker. he doesn't so much as sail, as it does smash the ice like a 13,000 ton hammer. once in position they throw a piston core, like a dart, at the

>> that doesn't sound good. >> after multiple attempts. >> go to the next up. hit it with a gravity core. >> a core sample look this is collected. inside the ship's lab, the multiyear process of investigating those cores, begins. what is your best guess. how old is this? >> so the base of this core -- probably is no more than 10,000 years. >> reporter: ann jennings with institute of arctic and alpine research. she says each core holds clues about peterman glacier's past. >> we didn't really expect to find things living under the ice shelf. we have. >> what have you found? sivisivides-storfi. >> easy for you to say. >> it is a seashell. single celled animal.

animal like all living creatures is made out of carbon allowing scientists to determine when they lived. take the depth scale here. convert it to age. then we can say when did the ice retreat? how quickly did it retreat? was there a lot of melt water coming out? >> you can get all of that from what looks like mud? >> yes. >> reporter: after a week in greenland, we headed home. but the scientists kept working. taking advantage of the final days of the short arctic summer. the 66 core samples they collected during their month at sea will be studied by scientists around the world for decades. >> this is the largest core repository in the world. >> a paleo climatologist at columbia university. he says cores collected in greenland are like a black box of the earth's inner workings. this one he collected south of

>> this is today's climate. we have had 10,000 years of relatively warm climate. then we go, 10,000 years in the past. boom. there is the last ice age. this is when long island was formed. cape cod was formed. go on. just find this color. this is filled with these rocks. ice rafted treditis. this period. whoa, a warm phase. cold phase. then another warm phase. short cold phase. longer warm phase. boom, another ice age. so you have had, cold, warm, cold, warm, cold -- warm. today. you can see the full report on our website. cbsnews.com. the overnight news will be right back.'re new liquid gels. and you're coming with me... you realize i have gold status? mucinex sinus-max liquid gels. dissolves fast to unleash max strength medicine. let's end this.

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