New iceberg breaks free in Antarctica

Scientists: Bergs not conclusive about global warming

A satellite image, taken Monday, shows the C-17 iceberg off Antarctica.

SUITLAND, Maryland (CNN) -- A rectangular iceberg more than twice the size of New York's island of Manhattan broke free from an Antarctic glacier this week, adding to the already high number of giant icebergs in southern waters.

Dubbed Iceberg C-17, the 58-square-mile berg shook loose from the Matusevich Glacier in the Ross Sea, an area in the part of the continent closest to New Zealand that's largely covered by the Ross Ice Shelf.

Antarctic researchers have noted an increase in the number of massive icebergs calved from the continent in recent years, an indication of warming temperatures.

Many observers have worried that the apparent warming conditions could be an early sign of the impacts of global warming. But in recent weeks, seemingly contradictory announcements have appeared to support claims of both warming and cooling trends.

Scientists involved in the studies, however, say the results say virtually nothing about global warming. Instead, they say, they're indicative of regional conditions -- a possible warming trend in the part of Antarctica that includes the Ross Sea, and a possible cooling trend elsewhere on the continent.

Only long-term, worldwide studies can confirm global warming, its causes and likely effects, scientists say.

Released in recent weeks were:

- A report in the journal Science that chronicled rising temperatures in a series of lakes near Antarctica's Weddell Sea.

- A report in the journal Nature that documented cooling temperatures in the West Antarctic Ice Sheet.

- A report from the National Science Foundation that found a one-degree Centigrade fall in temperatures since the 1960s in dry valleys near McMurdo Sound.

- A report from meteorologists at the United States' McMurdo Research Station of an unprecedented summer heat wave in early January, including first-ever temperatures above 50 degrees Fahrenheit.

The C-17 iceberg, still close to the Antarctic shoreline, is to be monitored by satellite imaging as it moves and shrinks or breaks up in seawater. The shipping industry has expressed concern that the high number of large bergs in southern waters could eventually pose a navigational hazard.

The National Ice Center, an agency jointly sponsored by several U.S. government scientific and defense entities, currently is monitoring the location of more than 40 massive icebergs near the Antarctic continent; the largest of these is dubbed Iceberg B-15-B. At 1,080 square miles, it's slightly larger than the state of Rhode Island. The Ice Center chart places it about 800 miles south of New Zealand.

The most northerly of these giant bergs is A-22-C, roughly 42 square miles in size. It has drifted to a point about 650 miles south of Cape Town, South Africa.