The hot blob in the Tasman Sea and extreme weather in Australasia

Australia’s Hot Ocean Blob Fuels Record Heat, Extreme Weather, Risk to Coral Reefs

Robertscribbler.,

21 December, 2017

Between Australia and New Zealand there’s a kind of climate change fed thing on the prowl in the off-shore waters. It takes the form of an angry layer of far warmer than normal surface water. And it’s been lurking around since late November.

(A hot, angry blob of much warmer than normal ocean temperatures has erupted between Australia and New Zealand.)

We can see this disruptive beast pretty clearly in the sea surface temperature anomaly maps provided by Earth Nullschool. Today’s readings show temperatures in this new blob hitting between 3.5 and 4.2 degrees Celsius above average across a broad expanse of ocean.

That’s much, much warmer than normal for this region of water. A place where 2 degree above average sea surface readings would tend to be unusual. But with global temperatures now hitting between 1.1 and 1.2 C above 1880s averages, we’re starting to see the climate dice more loaded for these kinds of extreme events. To be clear, this is not the kind of extremity we’d experience in a world at 2 C warming, or 4 C warming, or 7 C warming. But we’ve moved up the scale and weather, temperature, and ocean environmental conditions are being harmfully impacted.

(The above graph shows how temperatures have shifted outside of 20th Century ranges. During 2014-2017, the world dramatically warmed — generating further rightward movement in the bell curve. Temperature has an impact on everything from drought, to the severity of thunderstorms, to the length and intensity of fire season, to the fuel available for the most powerful hurricanes, to algae blooms, to coral bleaching events. Image source: NASA GISS.)

Back on November 30th, the blob contributed to an extreme rainfall event impacting Southeast Australia. One that dumped upwards of 10 inches or more in a rather short period. Since that time, South Australia has been seeing continued instances of extreme weather. Over recent days, towering supercell storms rocked Victoria with lightning, flash floods, damaging winds, and golf-ball sized hail. In Melbourne, a flood washed away a 40 foot section of a foot path. 

Meanwhile western parts of Sydney Australia were sweltering under record-shattering heat — with temperatures hitting a never before seen high of 111 F (44 C) on Tuesday, December 19th. Other regions experienced over 113 F (45 C) temperatures.

(Hot ocean blob feeds record breaking heat across Australia on Tuesday. Image source: WindyTV.)

The off shore hot blob is laying its hot, moist tendrils of influence on these weather extremes in a number of ways. First the blob is belching an enormous amount of moisture into the atmosphere above the local ocean. This moisture is being cycled over SE Australia by the prevailing winds and is adding convective energy to thunderstorms. In addition, the blob is also contributing to a sprawling ridge of high pressure that sits squarely over top it. The ridge, in turn, is baking parts of Australia with record hot temperatures.

Hot ocean blobs like the thing off Australia are a feature of human-caused climate change in that ocean and atmospheric warming generates an environment in which these pools of excessive warmth are more likely to form. These are anomalous events that stretch or break the boundaries of past weather and climate patterns by adding unusual amounts of heat and moisture to local and region climate systems in the environments in which they form. A hot blob forming off the U.S. West Coast during 2014-2015 contributed to a number of climate change associated events like the severe California Drought, a ridiculously resilient ridge of high pressure, western wildfires, intense rains into Alaska and Canada and a number of mortality events among sea life that were triggered by heat, low oxygen content, or blooms of harmful microbes that thrive in warmer ocean environment.

Though short-lived in comparison to the Hot Blob that lurked off the U.S. West Coast for the better part of two years, the Australia-New Zealand blob is already having a variety of atmospheric and oceanic impacts. Notably, in addition to the wrenching influences on local and regional weather described above, the blob is also contributing to risks to Australia’s corals.

(NOAA’s Coral Reef Watch shows strong risk of coral stress continuing through March of 2018. The hot blob of ocean water off Australia is contributing to a situation where reefs like the GBR are again at risk. Image source: NOAA.)

Over the past two years, the Great Barrier Reef (GBR) experienced back to back bleaching events. These were the worst ever seen by the reef. And they were triggered by human-caused climate change. This year, in part due to the blob, risks to corals between Australia and New Zealand are again high. If the blob shifts north and west, then the GBR again falls under the gun. This time for a third year in a row. Notably coral reef stress warnings and alerts abound throughout the zone between Australia and New Zealand in NOAA’s Coral Reef Watch report at present.

Due to the potential to continue to contribute to various weather and ocean impacts, the present climate change influenced hot blob between Australia and New Zealand bears continued monitoring. It has, however, already generated a number of impacts. And it is likely that more will follow.

CREDITS:

Hat tip to Carolyn Copeland

Hat tip to Guy Walton