Mallemaroking

Mark Brandon • October 15, 2024

I love looking at satellite images of the Antarctic and picking out the icebergs. In the last few years we have had great stories about the giant icebergs A68 in 2020, A76 in 2022 and most recently A23a currently in the Southern Scotia Sea.

At the moment there are two of very large icebergs at the southern end of Antarctic Sound. Here is a map to orientate yourself and show where they are.

A basemap with a MODIS image from 7 October 2024. The yellow box is the location of Antarctic Sound and is expanded on below.

There is a lot in the image above. As well as the Antarctic Peninsula there are clouds, sea ice, and icebergs. Zooming into Antarctic Sound shows the giant icebergs more clearly.

A MODIS satellite image of Antarctic Sound taken on 7 October 2024. Two large icebergs are at the southern end of the Sound. These are A80A and A76C.

And in the radar sensor on Sentinel-1 the icebergs leap out because that sensor “sees” through the clouds.

A Sentinel-1 SAR image from 8 October 2024. Land is coloured blue, the giant icebergs are solid grey, and sea ice and smaller icebergs make up the grey shades colouring the rest of the image.

A80A is 10×9 nautical miles and it calved from the Larsen D Ice Shelf in November 2022. A76C is currently 16×7 nautical miles and was part of iceberg A76 that calved from the Ronne Ice Shelf in May 2021. These are pretty decent sized icebergs: A80A looks to be pinned against Rosamel Island and Andersson Island at the southern end of Antarctic Sound, and A76C grounded against A80A.

Personally I would be surprised if they broke out before the start of the Antarctic season proper, so they could cause some complexities in navigating into the Weddell Sea through Antarctic Sound.

Finally we can’t forget the current monster of them all: A23A at 40×32 nautical miles, and it has been spinning above Pirie Bank north of the South Orkney’s since April 2024. I described it as “the iceberg that just refuses to die” when I spoke to the BBC, and it has been spinning for seven months in pretty much the same location. When it finally breaks free, it’ll head up towards South Georgia and it’s inevitable demise rapid demise.

A MODIS satellite image from 13 October 2024 showing iceberg A23A just north of the South Orkney Islands.

It’s amazing to think that A23A has been in existence since 1986 when it fractured from the Filchner-Ronne Ice Shelf.

The summary? It looks like if you’re going South this season you could see some very big icebergs, and navigation could be complicated in the North West Weddell Sea.

Posted in Science, Uncategorized. Tags: Antarctic Peninsula, Antarctic Sound, antarctica, iceberg, Icebergs on October 15, 2024 by Mark Brandon. Mark Brandon • September 26, 2019 Greenland’s ice sheet suffered major melting in July 2019, dumping billions of tons of meltwater into the Atlantic Ocena. Jennifer Latuperisa-Andresen/Unsplash, CC BY-SA

Mark Brandon, The Open University

The Intergovernmental Panel on Climate Change (IPCC) – the UN body responsible for communicating the science of climate breakdown – has released its long-awaited Special Report on the Ocean and Cryosphere in a Changing Climate.

Based on almost 7,000 peer-reviewed research articles, the report is a cutting-edge crash course in how human-caused climate breakdown is changing our ice and oceans and what it means for humanity and the living planet. In a nutshell, the news isn’t good.

Most of us rarely come into contact with the cryosphere, but it is a critical part of our climate system. The term refers to the frozen parts of our planet – the great ice sheets of Greenland and Antarctica, the icebergs that break off and drift in the oceans, the glaciers on our high mountain ranges, our winter snow, the ice on lakes and the polar oceans, and the frozen ground in much of the Arctic landscape called permafrost.

Read more: What is the cryosphere? Hint: It’s vital to farming, fishing and skiing

The cryosphere is shrinking. Snow cover is reducing, glaciers and ice sheets are melting and permafrost is thawing. We’ve known this for most of my 25-year career, but the report highlights that melting is accelerating, with potentially disastrous consequences for humanity and marine and high mountain ecosystems.

At the moment, we’re on track to lose more than half of all the permafrost by the end of the century. Thousands of roads and buildings sit on this frozen soil – and their foundations are slowly transitioning to mud. Permafrost also stores almost twice the amount of carbon as is present in the atmosphere. While increased plant growth may be able to offset some of the release of carbon from newly thawed soils, much will be released to the atmosphere, significantly accelerating the pace of global heating.

Sea ice is declining rapidly, and an ice-free Arctic ocean will become a regular summer occurrence as things stand. Indigenous peoples who live in the Arctic are already having to change how they hunt and travel, and some coastal communities are already planning for relocation. Populations of seals, walruses, polar bears, whales and other mammals and sea birds who depend on the ice may crash if sea ice is regularly absent. And as water in its bright-white solid form is much more effective at reflecting heat from the sun, its rapid loss is also accelerating global heating.

Glaciers are also melting. If emissions continue on their current trajectory, smaller glaciers will shrink by more than 80% by the end of the century. This retreat will place increasing strain on the hundreds of millions of people globally who rely on glaciers for water, agriculture, and power. Dangerous landslides, avalanches, rockfalls and floods will become increasingly normal in mountain areas.

All this melting ice means that sea levels are rising. While seas rose globally by around 15cm during the 20th century, they’re now rising more than twice as fast –- and this rate is accelerating.

Thanks to research from myself and others, we now better understand how Antarctica and Greenland’s ice sheets interact with the oceans. As a result, the latest report has upgraded its long-term estimates for how much sea level is expected to rise. Uncertainties still remain, but we’re headed for a rise of between 60 and 110cm by 2100.

Arctic sea ice is melting at an unprecedented rate, contributing to sea level rise. Netta Arobas/Shutterstock

Of course, sea level isn’t static. Intense rainfall and cyclones – themselves exacerbated by climate breakdown – can cause water to surge metres above the normal level. The IPCC’s report is very clear: these extreme storm surges we used to expect once per century will now be expected every year by mid-century. In addition to rapidly curbing emissions, we must invest millions to protect at-risk coastal and low-lying areas from flooding and loss of life.

Up to now, the ocean has taken up more than 90% of the excess heat in the global climate system. Warming to date has already reduced the mixing between water layers and, as a consequence, has reduced the supply of oxygen and nutrients for marine life. By 2100 the ocean will take up five to seven times more heat than it has done in the past 50 years if we don’t change our emissions trajectory. Marine heatwaves are also projected to be more intense, last longer and occur 50 times more often. To top it off, the ocean is becoming more acidic as it continues to absorb a proportion of the carbon dioxide we emit.

Collectively, these pressures place marine life across the globe under unprecedented threat. Some species may move to new waters, but others less able to adapt will decline or even die out. This could cause major problems for communities that depend on local seafood. As it stands, coral reefs – beautiful ecosystems that support thousands of species – will be nearly totally wiped out by the end of the century.

While the document makes some striking statements, it is actually relatively conservative with its conclusions – perhaps because it had to be approved by the 195 nations that ratify the IPCC’s reports. Right now, I would expect that sea level rise and ice melt will occur faster than the report predicts. Ten years ago, I might have said the opposite. But the latest science is painting an increasingly grave picture for the future of our oceans and cryosphere – particularly if we carry on with “business as usual”.

Read more: Not convinced on the need for urgent climate action? Here’s what happens to our planet between 1.5°C and 2°C of global warming

The difference between 1.5°C and 2°C of heating is especially important for the icy poles, which warm much faster than the global average. At 1.5°C of warming, the probability of an ice-free September in the Arctic ocean is one in 100. But at 2°C, we’d expect to see this happening about one-third of the time. Rising sea levels, ocean warming and acidification, melting glaciers, and permafrost also will also happen faster – and with it, the risks to humanity and the living planet increase. It’s up to us and the leaders we choose to stem the rising tide of climate and ecological breakdown.

Mark Brandon, Professor of Polar Oceanography, The Open University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Posted in Science. Tags: IPCC, SROCC on September 26, 2019 by Mark Brandon. Mark Brandon • April 26, 2019

On 25^th April 2019, the Arctic sea ice extent was 1.2 million km² below the 1981-2010 mean.

Sea ice in the Arctic currently ~1.2 million km² below the 1981-2010 mean. 25 April 2019.

If we compare the sea ice extent today, with the mean sea ice extent for the period 1989-93, the red colours show where there is currently relatively low sea ice.

The Arctic sea ice extent on 25 April 2019 (LHS), with the mean extent 25 April 1989-93. On the RHS blues = more sea ice than 89-93 mean, reds less sea ice.

As we expect the sea ice edge around virtually the whole Arctic has moved poleward compared with 1989-93, and there has been a lot written about the incredibly low sea ice extent in the Bering Sea over the last year year. For example this from twitter:

There is something significant going on in the Bering Sea: a very low ice extent for the second year in a row. pic.twitter.com/mrSlrT398Z

— Lars Kaleschke (@seaice_de) March 3, 2019

And of course this year follows on from the historic lows highlighted in spring 2018 by NASA.

Zooming in on Hudson Bay shows the current conditions there.

The Hudson Bay sea ice extent on 25 April 2019 (LHS), with the mean extent 25 April 1989-93. On the RHS blues = more sea ice than 89-93 mean, reds less sea ice.

On the west of Hudson Bay the sea ice is clearly 10-20% lower now than 1989-93 mean.  With a quick comparison of two MODIS satellite images just 1 day apart, you can see that the sea ice is mobile.

MODIS images from 21 and 22 April 2019 showing the heavily fractured sea ice in Hudson Bay.

What I think is happening is that the spring break up is coming earlier. If you look at the science literature you can see that the cycle of sea ice in Hudson Bay. This is from de la Guardia et al. (2017). I have added the shaded yellow box to show the time period we are looking at. When spring comes earlier that drop off as the sea ice decreases in concentration moves to the left, so the result is the sea ice is low compared with the 1989-93 mean.

Sea ice concentration (SIC) climatology in Hudson Bay from 1979 to 2000 (mean 1 SD). Estimated with Canadian Ice Service monthly SIC data (CIS; solid line with open triangles), passive microwave satellite SIC data from Comiso (1999) (PMW-BS; dashed line with open circles) and Cavalieri et al. (1996) (PMW-NT; solid line with open squares), and model run using realistic atmospheric forcing fields (NCEP; dashed line with dots), and using atmospheric output from the CGCM 3.1 (T64) – 20C3M run (solid line with open circles). Figure 2 From de la Guardia et al. (2017)

The early break up is on trend with the literature as well. For example, all of the blue dots in the grid below (From Kowal et a; 2017) show a trend for earlier sea ice breakup over the time period 1971-2011. In that paper they also show a trend to later freeze up as well, meaning the sea ice season is getting shorter in Hudson Bay.

Fig. 9 Significance of points according to the Mann-Kendall trend analysis for current analysis using ice-free dates. *p15% sea ice cover) 23 November 2017. From NSIDC.

I will write some more about this next week but for interest here is the Antarctic sea ice extent anomaly for 2017.

I made these movies using the excellent Antarctic Mapping Toolbox by Chad Greene. Antarctica is the Landsat Image Mosaic Of Antarctica (LIMA), and the coastline and shelf outlines come from the BEDMAP2 data set. Sea ice data is from NSDIC.

Posted in Science. Tags: anomaly, antarctica, sea ice, Weddell Polynya on November 24, 2017 by Mark Brandon. Mark Brandon • November 20, 2017

Antarctic sea ice extent remains low compared with the 1981-2010 median extent. This image shows the mean from 1989-93, the extent on 20 November 2017 and the difference between the two. Red colours imply that there is a decreased sea ice extent compared with the mean.

The mean Antarctic sea ice for the years 1989-93 on 20 Nov, the sea ice concentration on 20 Nov 2017 and the difference between the two data sets. Reds imply decreased sea ice compared with the mean, blue shades imply more. The original data come from the DMSP SMMI data set at the NSIDC.

And obvious low region is the vicinity of the Weddell Sea Polynya. I have written about the polynya this season on 17 September and 25 September, as well showing how it developed through the winter on 11 September 2017.

Something exciting is happening in the ocean under the polynya, and based on new data sources such as the SOCCOM buoy that surfaced in the polynya:

Last month, SOCCOM scientists were astonished to discover that a float in the Weddell Sea had surfaced inside the polynya, making contact with satellites in the dead of winter. Its new ocean measurements, transmitted when it surfaced, are being analyzed as part of a study in preparation on Weddell Sea polynyas. With these new observations comes the possibility that the polynya’s secrets may finally be revealed.

We should expect some exciting research articles soon.

Sea ice extent currently ~1.2 million km² low

The overall sea ice extent is currently ~1.2 million km² below 1981-2010 median extent. This sounds a lot.

Antarctic sea ice extent (with greater >15% sea ice cover) 18 November 2017. From NSIDC.

But at this time of the year the Antarctic sea ice is about to dramatically fall as spring develops. If spring “arrives” early then the extent will – as we see, be relatively low.

Seasonal cycle of Antarctic sea ice extent

Whilst the full on development and opening of the Weddell / Maud Rise Polynya is unusual, if you compare the sea ice on 18 November 2017 with the extent from the same day on 1989-1995 it is clear that the extent is often lower over Maud Rise, at this time.

This is the sea ice on 18 November for 1989, 91, 92, 93, 94, 95 and 18 November 2017. The original data come from the DMSP SMMI data set at the NSIDC.

I will keep watching the sea ice as the summer season develops

MODIS mosaic from the AQUA satellite on 18 November 2017.

** UPDATED 20th November 2017 replacing the first figure from 17  November to 20 November.

Posted in Science. Tags: antarctica, extent, Maud Rise, sea ice, SMMI, Weddell Polynya on November 20, 2017 by Mark Brandon.