Rapid Indian Ocean warming affecting marine plankton, fish stocks

The ocean heat uptake has doubled since 1997 resulting in warmer surface layers of the oceans, as well as increasing ocean warming at greater depths. One of the symptoms of this can be seen in the rapid warming of the Indian Ocean. This ocean has the largest warming trend in sea surface temperatures in the tropics over the past century. This has resulted in a 20 per cent reduction in primary plankton productivity for the period 1998 to 2013, contributing to reduced fish stocks and adding a threat to food security.

A North Atlantic nasty surprise: AMOC slowing faster than expected

Atlantic Meridional Overturning Circulation slowing much faster than expected

It seems that the 2004 Hollywood blockbuster disaster movie The Day after Tommorrow, while highly exaggerated, had the seed of scientific fact based upon the possible disruption that could occur from the slowdown or catastrophic cessation of the Atlantic ocean Meridional Overturning Circulation (AMOC), also known as the thermohaline circulation or Great ocean conveyor belt.

A new study by Rahmstorf et al (2015) published in Nature Climate Change has found evidence for a slowdown of the overturning circulation. This is based upon multiple lines of observation suggesting that over recent decades the current system has been weaker than ever before in the last century, or even in the last millennium.

The Gulf Stream is part of this circulation system with warm waters, which are naturally lighter, flowing north, and responsible for the mild climate of north western Europe. In the sub-polar region these waters cool, become more dense, and sink to the bottom before they start flowing south along the ocean bottom towards the tropics, then the South Atlantic and the Southern Ocean. The conveyor belt of currents connects the Atlantic, Indian, Pacific and Southern Oceans providing heat transfer and mixing throughout the globe.

Related Links: What’s going on in the North Atlantic? at Realclimate Blog | New Research Shows Exceptional Slowdown In Major Atlantic Ocean Currents Greg Laden's Science Blog

Guest Post: Atmospheric surface warming stalled by strong Trade winds driving heat into Pacific ocean

By Michael Hopkin, The Conversation, who interviewed Steve Rintoul from CSIRO, Richard Allan Professor of Climate Science at University of Reading, and Mathew England a Climatologist at University of New South Wales.

The “pause” in global warming since 2001 can be explained by the discovery of unusually strong winds in the Pacific, climatologists have found.

Global surface air temperatures have more or less flatlined since the turn of the century, prompting some observers to claim that the planetary warming trend has stopped. But the new research, published in Nature Climate Change, shows how stronger winds have driven the excess heat down into the ocean.

Researchers led by Matthew England, a professor of climatology at the University of New South Wales, began by looking at the differences between the 1990s, when Earth’s surface was strongly warming, and the 2000s, after the hiatus began.

Previous research has already shown that cooler temperatures over the eastern Pacific are linked to a slowdown in worldwide warming, but researchers wanted to know why.

Warming may spike when Pacific Decadal Oscillation moves to a positive phase

We are currently in a negative phase of the Pacific Decadal Oscillation, a cycle with phases that can last between 15 to 30 years. During a negative phase waters are cooler and heat mixes into deeper levels of the north Pacific ocean. When the next phase change ocurrs to a positive PDO we are likely to see some of the stored ocean heat released spiking atmospheric temperatures.

The Pacific Decadal oscillation was only identified by scientists in the 1990s, and we only have accurate observational data for identifying it going back some 50-60 years. Nathan J Mantua and SR Hare from the University of Washington in Seattle described the operation of the Pacific Decadal Oscillation in the Journal of Oceanography in 2002 (Mantua & Hare 2002 PDF). Read more about the PDO from the Climate Impacts Group from University of Washington.

Ocean Heat Content to 2000m continues warming

Ocean heat content has continued rising in the last 12 months to December 2013. This is observed in the top 700 meters of depth, as well as down to 2000 meters depth.

What pause in global warming? The Oceans take up about 93 per cent of the solar energy hitting the earth. The graphs show clearly there has been no let up in global warming, with oceans continuing to warm.

While atmospheric temperatures appear to have slowed over the last 15 years - a warming hiatus - but substantial warming is still occurring to the global system including adding heat to the world's oceans, melting Arctic sea ice, and the Greenland and Antarctic ice sheets.

Sea surface temperatures unusually warm around Australia in 2013

Sea surface temperatures around Australia in 2013 were unusually warm reported the Australian Bureau of Meteorology in it's annual climate statement. Record ocean temperatures were recorded for January and February, with November the second-highest on record. This continues a long term trend for increasing sea surface temperatures around Australia and globally.

Updates:

• Western Australian sea surface temperatures
• Sharks and warming waters
• Australian Seaweed species being pushed to the brink
• 2017 article: The Great White shark, climate change and ocean carbon cycles

Climate Departure: Oceans already outside historical variability as cities and ecosystems follow

Researchers from the University of Hawaii have estimated the year when we depart the climate variability we have historically known for cities around the globe. But the study also identifies that the planet's oceans have already passed their climate departure point, and that the greatest impact of global warming will be felt in biodiversity and ecosystems in the tropics.

In a study published in Nature - The projected timing of climate departure from recent variability (abstract) - researchers lead by Camilo Mora from the Geography Department at the University of Hawaii sought to identify the point at which the climate at 54,000 locations on Earth will exceed the bounds of historical variability. They used a baseline period of 1860 to 2005 to determine natural temperature variability. Using results averaged from 39 different climate models, they then determined for each location measured the year point in which the coldest years are likely to be consistently hotter than any of the past 150 years.

NOAA: Record Global Sea surface temperatures for August 2013

In August 2013 global sea surface temperatures (SST) set a new record. The August average sea surface temperature was 0.57°C above the 20th century average of 16.4°C (61.4°F), tying with 1998, 2003, 2005, and 2009 as the record highest for August.

This record warmth comes despite La Nina/El Nino (ENSO) neutral conditions in place for the last 16 months with below-average temperatures in the eastern equatorial Pacific.

Longterm sea level rise estimated at 2.3 metres for every degree Celsius of global warming

"Continuous sea-level rise is something we cannot avoid unless global temperatures go down again," said climate scientist Anders Levermann from the Postdam Institute for Climate Impact Research. "Thus we can be absolutely certain that we need to adapt. Sea-level rise might be slow on time scales on which we elect governments, but it is inevitable and therefore highly relevant for almost everything we build along our coastlines, for many generations to come."

Anders Levermann was taking about the implications of a new study he is a co-author of - The multi-millennial sea-level commitment of global warming. The study is published in the Proceedings of the National Academy of Sciences online during July 2013. It is one of the first studies to combine analyses of four major contributors to potential sea level rise into a collective estimate, and compare it with evidence of past sea-level responses to global temperature changes.

The result is a longterm estimate that global sea levels will rise about 2.3 meters, or more than seven feet, over the next two thousand years for every degree (Celsius) the planet warms. "the total sea-level commitment after 2,000 y is quasi-linear, with a sensitivity of 2.3 m °C" reports the study.

"The study did not seek to estimate how much the planet will warm, or how rapidly sea levels will rise," noted Professor Peter Clark, an Oregon State University paleo-climatologist and co-author on the PNAS article. "Instead, we were trying to pin down the 'sea-level commitment' of global warming on a multi-millennial time scale. In other words, how much would sea levels rise over long periods of time for each degree the planet warms and holds that warmth?"

Heading for cooler waters - Climate Change Impact of warming oceans on global fish stocks

For the first time scientists have demonstrated the impact of climate change on ocean warming and sea surface temperatures affecting global fisheries stocks. Previous studies were limited to individual fisheries. The changes have been occurring clearly since the 1970s, the scientists say. The implications of this research raises the need for timely changes in fisheries management practices and adaptation plans for communities dependant on fishing, particularly climate vulnerable developing countries in the tropics.

"Given global fisheries contribute hugely to the world's economy and food security, this is a significant finding," said co-author Dr Reg Watson from the University of Tasmania's specialist Institute for Marine and Antarctic Studies."We are no longer talking about future hypotheticals - we are talking about impacts on a global scale that we can already demonstrate."

Previous research by Dr Watson published last year demonstrated that marine fishes are now smaller in size. "Last year we showed that one of the consequences of climate change and excessive fishing is that globally marine fishes are smaller," said Dr Watson.

The paper - Signature of ocean warming in global fisheries catch - was published in Nature on 15 May 2013. The study was lead by Assistant Professor William Cheung, University of British Columbia, with collaboration from Professor Daniel Pauly and Dr Reg Watson.

I wrote about a related issue on the Velocity of climate change imperiling ocean diversity, particularly with regard to Australia, in January 2012.

Antarctic Paradox: ocean warming melting ice shelves causing sea ice expansion

Antarctic sea ice extent is a complex and puzzling beast, not following a simple process of rapid Arctic sea ice diminishment. A new paper in Nature Geoscience argues that warm deep ocean currents are contributing to ice shelf melt and causing Antarctic sea ice expansion. While ice mass loss from Antarctica is presently at 250 Gigatonnes per year and accelerating, sea ice is also expanding slowly but to record levels. What a paradox!

The trend for a gradual increase in Antarctic Sea ice has puzzled scientists for some time. The expansion is at odds with general climate model results. I reported on the puzzle of Record Antarctic Sea Ice Growth in November 2012. In that article I explained that (Holland et al 2012) argued that atmospheric variability in the form of local winds was pushing the ice northwards creating space for new sea ice to form. While climate deniers claimed record Antarctic sea-ice was a refutation of climate change, in reality it showed they could not fathom that the cryosphere and the planet's climate are complex processes which we are still trying to understand, with some surprising processees not readily open to be modelled.

Guest Post: Deep Ocean warming Confirms Global Warming Has Accelerated

New Research Confirms Global Warming Has Accelerated (via Skeptical Science)

Posted on 25 March 2013 by dana1981 A new study of ocean warming has just been published in Geophysical Research Letters by Balmaseda, Trenberth, and Källén (2013). There are several important conclusions which can be drawn from this paper. Completely contrary to the popular contrarian myth,…

Southern Ocean warming impact on Antarctic Ice Sheet and global sea level rise

Climate change is causing the southern ocean to warm and freshen which will melt ice shelves and glacier tongues affecting glacier discharge and producing Antarctic Ice Sheet mass loss and global sea level rise. A new study shows that small temperature changes of the Southern Ocean can contribute to far-reaching changes on the Antarctic ice sheet that could lead to substantial future sea-level rise.

Related: Waking the giant: Global Warming in the Weddell Sea, West Antarctic Ice Sheet and sea level rise | Attenborough warns of ice shelf destruction in Antarctica | Global Warming in Antarctica: Thwaites and Pine Island Glaciers accelerating, West Antarctic Ice Sheet losing mass

Seagrass meadows are key carbon sinks for combatting climate change

May 22 is UNESCO's
 International Day for Biological Diversity which focussed strongly on conserving our marine diversity. One of the important marine ecosystems are the seagrass meadows around the coasts of the world. A new global scientific research study just released has shown that seagrass meadows store significantly more carbon than any land based forest. They are very important as carbon sinks. But they are also suffering a major decline due to pollution from agricultural and mining development and chemical runoff, coastal development changing water turbidity upsetting photosynthesis in seagrass, and increasing sea surface temperatures affecting seagrass growth due to global warming.

The new global study of seagrass meadow ecosystems has found that coastal seagrass beds store much more carbon than can be stored in even the most carbon dense forests, such as the temperate native forests of Victoria. Seagrass meadows can store up to 83,000 metric tons of carbon per square kilometre, mostly in the soils below them. In comparison, a typical land forest stores around 30,000 metric tons per square kilometre mostly as wood. It is the first global study to analyze the carbon storage capacity in seagrasses.

Seagrass meadows support a highly level of biodiversity with many fish species using the seagrass during their juvenile period, as well as providing homes for crabs, sea urchin, seahorses shrimp and prawns. Sea tutles, dugongs and manatees depend on seagrass meadows as a primary food source. As Professor Carlos Duarte points out in an article on The Conversation website, Indigenous cultures new the significance and value of seagrass meadows. Conservation and restoration of seagrass ecosystems provides a unique Submarine Carbon Tax Opportunity! Seagrass meadows are intense, but fragile carbon sinks.

More Information: Seagrass Watch | Global Seagrass Monitoring Network

Global Warming intensifying Global Water Cycle by double current climate model projections

New research into ocean salinity levels has revealed a strong global water cycle intensification during the period of 1950 to 2000. The researchers report the rate of change in the global water cycle is double the rate projected by current-generation climate models. The study found "robust evidence of an intensified global water cycle at a rate of about eight per cent per degree of surface warming," said study co-author Dr Durack, a post-doctoral fellow at the Lawrence Livermore National Laboratory in the US.

Ocean acidification increasing at unprecedented rate not seen in last 300 million years

In a new study marine scientists warn that the rate of ocean acidification presently occurring is unprecedented in the last 300 million years. This is due to dissolving carbon dioxide from the atmosphere, much of which human activity has contributed over the last 200 years through the use of fossil fuels. The extent of the acidification and rate of acidification enhances the prospect for a mass marine extinction event this century.

Related: Dec 2011 - Ocean acidification warning to Durban climate negotiators to act on reducing CO2 emissions | June 2011 - Oceans at high risk of unprecedented Marine extinction scientists warn | April 2010 - Paleo-perspectives on ocean acidification - marine ecosystems under threat | Feb 2010 - Marine Extinction looms with Ocean Acidification increasing

Sea Cucumber poo moderates impact of ocean acidification on coral reefs

Ocean acidification is a major threat to coral reefs and other marine zooplankton and creatures using calcium carbonate shells. Marine and Climate scientists working at the University of Sydney's research station, One Tree Island, on the Great Barrier Reef have discovered that sea cucumber poo increases the alkalinity of the reef water providing a buffer to the increasing acidity caused by ocean acidification.

It is a vital marine process that provides some buffer to corals with the impacts of ocean acidification. "We have found that sea cucumbers play a vital role in reducing the harmful impact of ocean acidification on coral growth," said Professor Maria Byrne, the director of One Tree Island Research Station.

Ocean acidification warning to climate negotiators to act on reducing CO2 emissions

Climate negotiators in Durban were urged to consider ocean acidification and changes taking place in the southern ocean due to increasing greenhouse gas emissions and climate change. The International Union for the Conservation of Nature (IUCN) and ocean researchers released important briefings on ocean acidification and changes taking place in the southern ocean on November 29, 2011.

At the United Nations Framework Convention on Climate Change (UNFCCC) Durban climate talks the IUCN and Ocean Acidification Reference User Group urged that Ocean acidification should no longer remain on the periphery of the international debates on climate change and the environment and should be addressed by the UN Framework Convention on Climate Change and other global environmental conventions. At the same time ocean researchers in Australia also released a position analysis paper that the southern ocean was undergoing major changes in becoming warmer, even at great depths; more acidic; and freshening with a drop in salinity levels.

Related: Oceans at high risk of unprecedented Marine extinction scientists warn | IUCN - The acid truth about our oceans: experts urge action to limit ocean acidification | ACE CRC - Research shows that Southern Ocean is warming and freshening

Sea Surface Temperatures around Australia remain elevated, La Niña builds slowly

The Sea Surface temperature Anomaly around Australia in November 2011 remains elevated. A slow cooling in the tropical mid Pacific indicates that La Niña is also slowly building. A persistently warm Indian Ocean is also a main driver for forecast wetter conditions in Australia this summer.

Scientists Estimate Sea level Rise for next 500 years

Rising seas are one of the more long-term catastrophic effects of global warming that will not end at 2100, even with the most drastic emission reductions, but will continue for centuries. Researchers based at the Niels Bohr Institute in Copenhagen have calculated the long-term outlook for the next 500 years for rising sea levels in relation to the emission of greenhouse gases and pollution of the atmosphere using a climate model calibrated against actual historical measurements of sea level rise.

The change in sea levels is driven by massive inertia in the earth's climate system. With anthropogenic global warming melting the Greenland ice sheet and mountain glaciers and warming the oceans, the processes causing sea level rise are now underway and accelerating. Increasing Groundwater extraction for agricultural and mining use is also a small but notable contribution to sea level rise.

Caption: The graph shows how sea levels will change for four different pathways for human development and greenhouse gas pollution. The green, yellow and orange lines correspond to scenarios where it takes 10, 30, or 70 years before emissions are stabilized. The red line can be considered to represent business as usual where greenhouse gas emissions are increasing over time.

Related: Sea Level Rise and Australia | Report assesses climate risks of sea level rise for Australia | Impacts of rising sea level a wake up call on climate change | Scientists confirm Rising Sea Levels may exceed one metre this century | The risks of Sea Level Change - Dr Peter Ward | NASA Climatologist Predicts Disastrous Sea Level Rise