Much like the other glaciers around Mt. McKinley, climbers are often found on the Kahiltna Glacier. During May and June the Kahiltna becomes a miniature international airport. People from around the world travel by ski plane to a base camp at 7,000 feet and from there they set out on adventures not only to the summit of Mt. McKinley but also to nearby Mt. Foraker, Mt. Hunter and other peaks of the Alaska Range. As many as 600 climbers each summer ascend Mt. McKinley using the famous West Buttress route. As climbers toil with the difficulties of traveling on the glacier and slowly making their way toward the summit, the glacier beneath their feet steadily transports tons of ice in the opposite direction. Like a huge conveyor belt, the Kahiltna Glacier has moved ice for centuries from 13,000 feet to about 1,000 feet above sea level. Over the last decade, twice-yearly measurements of snowfall and snowmelt have indicated that, like many other glaciers in Alaska and other parts of the world, this great glacier is shrinking. Closer to the terminus and many feet above the present glacier's surface, cuts in the sides of the valley are observable, where the glacier surface existed only a century ago. Brought upon by fluctuations in climate, Changes to glaciers like the Kahiltna are caused by climate fluxuations, currently there is increasing melting. This effect, combined with melting on the much larger coastal glaciers of Alaska contribute more to rising sea level than the immense ice sheet that covers Greenland, which is also melting rapidly.