Accelerating Sea Level Rise is Being Driven by Rapidly Increasing Melt From Greenland and Antarctica

From 1993 to the present day, global sea level rise has accelerated by 50 percent. And the primary cause, according to recent research, is that land glaciers such as the massive ice sheets of Greenland and Antarctica are melting far faster than they have in the past.

(Assessment of factors involved in the presently increasing rate of global sea level rise.)

Antarctica, in particular, is melting much more rapidly — with melt rates tripling in just the last ten years.

The primary factors contributing to global sea level rise include thermally expanding oceans and the melting of ice on land. During the decade of 1993 to 2004, the World Meteorological Organization notes that oceans rose by 2.7 mm per year. During this time, land ice sheets amounted to 47 percent of that rise — or about 1.35 mm. The same report found that from 2004 to 2015, oceans rose by around 3.5 mm per year and that land ice contribution had risen to 55 percent (1.93 mm per year). Looking at sea level measurements from AVISO, we find that from March of 2008 to March of 2018, the average rate of sea level rise accelerated further to 4.3 mm per year.

The net takeaway is that the rate of global ocean rise has increased by more than 50 percent since the early 1990s and that this acceleration has been driven by increasing melt from large land glaciers like those in Greenland and Antarctica.

(Sea level rise contributors as reported by the World Meteorological Organization in its 2017 report on the state of the global climate.)

Over the coming years and decades, this rate of rise is likely to continue to accelerate — surpassing 5 mm per year sometime rather soon, and likely exceeding the 1 cm per year mark by the 2040s through the 2060s. Melt rates will likely increase substantially as we approach the 1.5 C and 2.0 C warming marks. However, the net heat pressure from fossil fuel emitted greenhouse gasses will also drive sea level rise rates. As a result, it is imperative that we work to cut fossil fuel emissions more rapidly and that we pursue a swift as possible transition to clean energy.

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A Delaware-Sized Iceberg is About to Enter the Southern Ocean — Loss of Larsen C Ice Shelf Possible in Near Future

A rift in West Antarctica’s Larsen C Ice Shelf is about to expel a 1,000 foot tall, Delaware-sized iceberg into the Southern Ocean. The crack began to form in 2011. But over the past year, it has expanded rapidly. Now this massive, newly-forming iceberg hangs by just a thin 13 kilometer wide thread.

As you can see from the above Sentinel 1 animation posted by Adrian Luckman, rift progression has occurred in large leaps as pressure on the shelf reached various breaking points. New additions to the rift have often been in jumps of 20 kilometers or more of rift length in numerous instances over the past year. With just 13 kilometers of connecting ice remaining, the entire state-sized iceberg could now break off at any time.

According to Project Midas, late June observations show the crack continuing to widen at the rate of about 2 meters per day. So the larger section of the newly-forming berg is progressing toward the Southern Ocean at a rather rapid rate. And this movement is increasing strain on the small remaining ice bridge to the larger Larsen C Shelf.

Once the massive berg breaks off, researchers are concerned that it could precipitate a larger collapse of the Larsen C Ice Shelf itself. Such an event would be the third ice shelf loss along the Antarctic Peninsula during recent decades. A series of ice shelf collapses precipitated by warming oceans and atmospheres induced primarily by fossil fuel burning.

(Many cities are already suffering from rising ocean levels. However, future rates of sea level rise can increase considerably over present rates depending on how rapidly glaciers and ice shelves are taken down by human-forced warming. Image source: Tamino.)

Such ice shelf losses are a rather serious affair as they release the glaciers behind them — allowing these massive ice forms to enter the world ocean more rapidly and thus increasing the rate of global sea level rise. Already, numerous cities, islands and nations are under threat from oceans presently rising at the rate of 3.3 millimeters per year globally. But loss of buttressing ice shelves like Larsen C and others around Antarctica and Greenland may double the present rate of rise many times over.

At a recent meeting of over 250 U.S. Mayors in Miami to discuss how climate change is presenting a serious threat to cities, New York’s Bill de Blasio told reporters: “Miami Beach is facing, literally, an existential crisis.” But it’s not just Miami that’s under the gun. It’s pretty much every coastal town, city, state and nation around the world. And Larsen C is just one of the most recent sea level rise canaries to begin to show signs of ailing in the global warming coal mine.

Links:

Project Midas

A New Crack in One of Antarctica’s Largest Ice Shelves Could Mean a Major Break is Near

Miami Beach Mayors Talk Global Warming

Tamino

Hat tip to Abel

Note: 1,000 foot tall reference includes freeboard + below water line measure.

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