Isostatic rebound Amundsen Bay: a negative feedback that acts on West Antarctic grounding line retreat

In our series ‘Understanding Sea Level Rise’ we’ve paid ample attention to positive melting feedbacks, mechanisms that accelerate ice melt and ice sheet dynamics as global temperatures keep rising. Now of course there are also negative feedbacks, like local relative sea level lowering around ice sheets (due to decreasing gravitational pull and isostatic rebound as the ice mass shrinks), a factor that can influence the position of the grounding line of West Antarctic glaciers, the line that separates where these glaciers move across bedrock and where they start floating, forming ice shelves. In general these grounding lines are retreating as a consequence of a warming water wedge and thinning of the ice shelves and the actual ice sheet, however the local relative sea level lowering as a result of this ice loss has the opposite effect, promoting an advance of these grounding lines – therefore acting as a stabilising factor for West Antarctic glaciers, like the Twaites Glacier and Pine Island Glacier, glaciers that are potentially important contributors to acceleration of 21st century sea level rise.

Now we presume you want to know which feedbacks are (likely to be) dominant in this area, the positive or the negative feedbacks. Well, apart from reading the title of this article you can also click it, to learn more…

Grounding lines under West Antarctic Ice Sheet
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Climate Change & Anthropocene Extinction 44: Building corridors can increase species survival 5-18%

In face of the Holocene-Anthropocene Mass Extinction conservationists challenge themselves to think of novel biodiversity protection measures. Thinking outside of the box of fenced reserves is literally required, as over 85 percent of Earth’s land does not have nature-protected status, and many stressors, including climate change, also hit home inside nature reserves, decreasing potential refugia in size.

One solution might be to invest in corridors, connecting climate-sturdy refugia, and helping threatened species reach suited habitat.

Local species extinction risk under various climate change scenarios
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Climate Change & Anthropocene Extinction 43: Expert explains biodiversity graph Royal Society report

It’s the end of the year so a good time to evaluate where we’re standing. Our climate-biodiversity series has progressed to episode 43. If you’ve missed it, we highly recommend you start at part 1, preferably under a Christmas tree (in a biodiverse spruce forest) with family. Sadly we cannot guarantee snow.

It’s also a very good time to try to summarise what we’ve been able to learn from the global community of climate researchers, our somewhat classical friends at the Royal Society thought. It’s been a while since the last IPCC report (AR5, 2013/2014) and apart from interesting upcoming IPCC publications about sea level rise and the important 1.5 degrees target it’ll be another long while until the next full-blown climate report will be released (IPCC AR6, 2022).

Let’s bridge that gap, the Royal Society thought – and compile our own climate updates report!
Biodiversity extinction risk under climate change - Mark Urban metastudy in Royal Society report
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Climate Change & Anthropocene Extinction 42: Do grass-eating Arctic geese suffer a climate mismatch?

Arctic geese like the Barnacle goose that breed on the Russian tundra and winter in the Netherlands need to increase the speed of their return trips, as the tundra spring starts weeks earlier – possibly skipping their fuelling stops on Baltic islands and along the White Sea, a model study shows.

Barnacle geese migrating between wintering and Arctic breeding grounds
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Climate Change & Anthropocene Extinction 41: Arctic bird shrinks due to mismatch with tundra insects

Many Arctic species are shrinking in size. Say what? Yes, shrinking in size – polar bears included. Is this some clever climate adaptation (as the opposite holds true: larger body sizes are an adaptation to a cold climate), or is it a sign of increasing malnourishment?

Well, the latter – at least in the case of the red knot (Calidris canutus), a long-distance migratory bird that breeds on the Russian Arctic tundra and winters in tropical West-Africa, using temperate zone tidal wetlands as a refuelling stop on their long road.

Red knots over the Dutch Wadden Sea - Kasper Hendriks
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Climate Change & Anthropocene Extinction 40: Warming changes spread of European ash tree dieback

Under very rare circumstances a spatial mismatch caused by climate change can be a good thing. But before you start betting on compensating one ecological disturbance with another that’s possibly even more dangerous, we think perhaps we should discuss another solution now that forest plagues seem to be increasing everywhere around us.

Ash tree dieback plague, climate change vs biodiversity
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Climate Change & Anthropocene Extinction 39: Warming also causes spatial mismatch interacting species

Climate change can cause a ‘temporal mismatch’ between interacting species, we learned in our previous article. Here’s a short appendix to that piece, illustrating how simultaneously also a spatial mismatch can develop – further promoting population declines and biodiversity loss, especially in Earth’s temperate climate zones.

European butterfly-host plant spatial mismatch caused by climate change
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Climate Change & Anthropocene Extinction 38: European migratory birds offer early climate warning

Migratory birds may seem to be well equipped to cope with the consequences of climate change, because their trait of seasonal migration is of course already an evolutionary adaptation to temperature fluctuations that characterise the seasons of Earth’s temperate climate zones.

But as we have discussed in our special piece about the effects of climate change on temperate zone biodiversity – it’s far more complex, and having evolved under relatively high natural temporal climate variation may actually be a handicap, when trying to adapt to globally rising temperatures under anthropogenic climate change. And birds migrating between Africa and Europe may be ahead of Asian and American species, facing early consequences.

Climate change affects migratory birds between Europe and Africa
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Climate Change & Anthropocene Extinction 37: If the sea ice goes, so does the Arctic ecosystem

All life forms that depend on Arctic sea ice will be hurt when that sea ice disappears. And especially when you also depend on other life forms that depend on sea ice. Polar bears are an obvious example (and if you go a bit deeper humans are also included).

We’ll skip the humans and talk about polar bears in a bit, but let’s first talk about the underlying issue: what science means – and how it’s actually quite easy to harness your own intelligence to interests that may want to try to confuse you. Yes, a scientific mind – a joy forever.

Arctic marine ecosystem: many species (inter)dependent on sea ice - including polar bears
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Climate Change & Anthropocene Extinction 36: Ocean plastic outpaces warming & CO2 in race to bottom

Earth’s oceans currently take up almost 50% of our CO2 emissions and absorb over 90% of the heat the other half of the CO2 traps in the atmosphere. Both ocean CO2 and heat absorption will have major consequences for deep-sea ecosystems, like ocean acidification, ocean anoxia, and increasing food scarcity – impacts that take a long time before they reach rock bottom, at several kilometres depth.

But at the same time humans are also doing something else: we’re also dumping hundreds of millions of tonnes of plastic trash into these same oceans. And for deep-sea organisms, that ocean crisis seems to hit home much faster…

Deep ocean plastic pollution - Mariana Trench
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