Back to the Anthropocene! Arctic Sea Ice Edition

By David Middleton – Re-Blogged From WUWT

Do you ever get tired of smarmy, snot-nosed articles like this?

Obituary: Remembering the Holocene Epoch

BY CHRIS WILSON
AUGUST 29, 2016

The Holocene Epoch, which witnessed milestones from the development of Crater Lake to the invention of the electric guitar, died prematurely Monday in Cape Town at the age of 11,650. It is survived and succeeded by the Anthropocene Epoch.

The cause of death was the rapid alteration of the earth’s ecosystem due to nuclear weapon tests, micro-plastic pollution, agriculture, carbon emissions and other human contributions to the changing environment, according to the Anthropocene Working Group. News of the Holocene’s death could not be independently confirmed by the International Geological Congress, which is conducting a review of the evidence surrounding the epoch’s death.

If confirmed, the Holocene’s death at eleven-and-a-half millennia would make it by far the shortest-lived of its ancestors. Its immediate predecessor, the Pleistocene Epoch, died at over 2.5 million years old, while the Eocene Epoch survived to be nearly 22 million. But even for an epoch cut so tragically short, its accomplishments stand out.

“It set up these Goldilocks conditions for human civilization to take off,” says Nicholas Spano, a graduate student researcher at the Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley. “During the Holocene, earth’s climate as a whole became much more stable.”

[…]

Time Magazine

Notes to Chris Wilson:

  • After 10 years of lobbying the media, the Anthropocene Working Group has yet to produce a coherent recommendation for an Anthropocene Epoch and it is a near certainty that they will never produce a recommendation that could even come close to approval.
  • Why in the Hell would you consult with a biology grad student, working in a museum, about the climate of the Holocene?
  • Which Goldilocks conditions? Most of the Holocene was much warmer, with higher sea levels and less ice than today.
  • Your smarmy snot-nosed diatribe is “not even wrong.”

This article is far less smarmy and snot-nosed, but still “not even wrong.”

Anthropocene in the Arctic
A behind the scenes account of how the scientific community came to terms with the changing landscape of the Arctic

By Anant Misra
Last Updated: Monday 28 January 2019

“But the Arctic tells no lies” — It is with these words that Mark C Serreze closes the last chapter of his book, Brave New Arctic. The words are at once mournful as well as menacing. What makes them truly ominous is that throughout the book, Serreze’s tone remains neutral and matter-of-fact, sometimes painfully so. Soon after discussing the declining population of polar bears—which he takes care to point out is due to a variety of factors—Serreze cheerfully mentions that bowhead whales are actually doing quite well as the loss in seaice has led to a bounty of food supply.

As is evident from the aforementioned example, climate change is a complex phenomenon—one whose effects are still not entirely understood even by those who have spent a lifetime studying it. It is this complexity which drives the book and comes across as its most prominent theme. Serreze is forthright in admitting that throughout the 1990s and early 2000s, the scientific community was not clear on how to best distinguish human footprints of global warming from natural climate variability. This was mostly due to unreliable accounts and records which did not go far back enough to provide sufficient data for mapping climate change.

[…]

Down to Earth

The Anthropocene doesn’t exist… It’s not even wrong. But, in the spirit of ridicule, I will pretend that it does exist for the duration of this post.

Insufficient data

Allow me to repeat the last paragraph of Anthropocene in the Arctic:

As is evident from the aforementioned example, climate change is a complex phenomenon—one whose effects are still not entirely understood even by those who have spent a lifetime studying it. It is this complexity which drives the book and comes across as its most prominent theme. Serreze is forthright in admitting that throughout the 1990s and early 2000s, the scientific community was not clear on how to best distinguish human footprints of global warming from natural climate variability. This was mostly due to unreliable accounts and records which did not go far back enough to provide sufficient data for mapping climate change.

Mark Serreze has been the Director of the National Snow and Ice Data Center since 2009. NSIDC publishes a daily Arctic Sea Ice News and Analysis. Whenever someone says something like this, “Arctic sea ice extent for September averaged 4.32 million square kilometers (1.67 million square miles), the third lowest in the 41-year continuous satellite record, behind 2012 and 2007″, they’re usually citing the NSIDC. When the record length is only 41 years, “third lowest” doesn’t tell us very much. As noted in the article about Dr. Serreze, the “records which [do] not go far back enough to provide sufficient data for mapping climate change.”

In addition to lacking climate-relevant context, the measurements also lack a size context.

Figure 1. “Monthly September ice extent for 1979 to 2019 shows a decline of 12.9 percent per decade.” Credit: National Snow and Ice Data Center
High-resolution image

Is 4.32 million square kilometers small? Medium? Large? Geologists are big on context and scale. When a geologist takes a picture with a person in it, the person is just for scale. Since quarters, lens caps and rock hammers are far too small to contextualize 4.32 million square kilometers, we need something bigger.

The Arctic Ocean is the smallest of the world’s five oceans (after the Pacific Ocean, Atlantic Ocean, Indian Ocean, and the Southern Ocean). The Northwest Passage (US and Canada) and Northern Sea Route (Norway and Russia) are two important seasonal waterways. In recent years the polar ice pack has receded in the summer allowing for increased navigation and raising the possibility of future sovereignty and shipping disputes among the six countries bordering the Arctic Ocean (Canada, Denmark (Greenland), Iceland, Norway, Russia, US).

Area:
total: 14.056 million sq km

CIA World Fact Book

Figure 2. The “smallest of the world’s five oceans” doesn’t look so small from above. (NSIDC)

What percentage of the Arctic Ocean is covered by 4.32 million square kilometers of sea ice?

Figure 3. Arctic sea ice extent as a percentage of Arctic Ocean surface area. (Data from NSIDC)

Now we have some context and scale. 4.32 million square kilometers is 31% of the Arctic Ocean… Just a bit below the climate “normal” range. Doesn’t sound like much of a death spiral to me. Bear in mind that the satellite record started right about here:

Figure 4. Science News March 1, 1975 That 70’s climate normal.

However, 41 years is much too short of a record length to determine what the climate “normal” should be. Fortunately, there have been efforts to reconstruct sea ice extent prior to the satellite record.

Figure 5. Arctic sea ice before satellites. “Sea ice charts of the Arctic Ocean show that ice extent has declined since at least the 1950s. Credit: NSIDC and the UK Hadley Center” (NSIDC)

To look back into the past, researchers combine data and records from indirect sources known as proxy records. Researchers delved into shipping charts going back to the 1950s, which noted sea ice conditions. The data gleaned from those records, called the Hadley data set, show that Arctic sea ice has declined since at least the mid-1950s. Shipping records exist back to the 1700s, but do not provide complete coverage of the Arctic Ocean. However, taken together these records indicate that the current decline is unprecedented in the last several hundred years.

NSIDC

“The current decline is unprecedented in the last several hundred years” is a big No Schist Sherlock. Earth has been warming from the coldest climate of the Holocene (the Little Ice Age) for the last 400-500 years.

Kinnard et al, 2008, pieced together a reconstruction back to 1870…

Figure 6. Maximum and minimum sea ice extent, 1870-2003 (Kinnard et al, 2008).

Again, this lacks context and scale. Let’s plot it as a percentage of the Arctic Ocean surface area.

Figure 7. Maximum and minimum sea ice extent, 1870-2003, as % Arctic Ocean (Kinnard et al, 2008).

And now at the same scale as the NSIDC data.

Figure 8. That “death spiral” keeps on getting flatter.

According to the Kinnard reconstruction. The Arctic Ocean still has about half as much summer sea ice as it did at the end of Neoglacition, the maximum extent of Holocene glaciers and sea ice. Why is this a bad thing? Since 1870, Arctic sea ice has been retreating from this sort of climate “normal”…

Figure 9. Yeah, it’s just a movie. (Quartzy)

But these disastrous polar expeditions were real.

Kinnard also featured a neat map:

Figure 10. Probability of sea ice occurrence (1870-2003) A = maximum, B= minimum. (Kinnard et al., 2008)

Ok… So the minimum summer sea ice covered about twice as much area for 90% of the past 150 years… So what? Is 150 years a long time? Is it relevant to the Holocene Epoch? Is it one of the “Goldilocks conditions” of the Holocene? We clearly need more context and scale.

Back to the Anthropocene!

Stein et al., 2017 (H/T tty) provides a great description of a rather novel method of determining paleo sea ice extent.

In a pioneering study by Belt et al. (2007), the ability to (semi-)quantitatively reconstruct paleo-sea ice distributions has been significantly improved by a biomarker approach based on determination of a highly branched isoprenoid (HBI) with 25 carbons (C25 HBI monoene = IP25). This biomarker is only biosynthesized by specific diatoms living within the Arctic sea ice (Brown et al., 2014) and appears to be a specific, sensitive and stable proxy for Arctic sea ice in sedimentary sections representing Late Miocene to Recent times (Stein et al., 2012, 2016; Belt and Müller, 2013; Stein and Fahl, 2013; Knies et al., 2014). The presence of IP25 in the studied sediments is direct evidence for the presence of sea ice.

[…]

For more semi-quantitative estimates of present and past sea ice coverage, M€uller et al. (2011) combined the sea-ice proxy IP25 and phytoplankton biomarkers in a phytoplankton- IP25 index, the so-called ‘PIP25 index’:

PIP25 = [IP25]/([IP25] + ([phytoplankton marker] x c))

with c is the mean IP25 concentration/mean phytoplankton biomarker concentration for a specific data set or core.

[…]

Stein et al., 2017

This schematic diagram from Belt et al., 2013 relates the PIP25 index to sea ice conditions:

Figure 11. Relationship of sea ice conditions to PIP25 index (Belt ea al., 2013). Click to enlarge.

Generally speaking, the PIP25 index correlates to sea ice extent as follows:

  • >0.7 = Extended, perennial (year-round) ice cover
  • 0.5-0.7 = Seasonal ice cover/ice edge situation
  • 0.1-0.3 = Reduced ice cover
  • <0.1 = Ice-free year-round

Here’s an example from the Chukchi Sea:

Figure 12. Sediment core ARA2B-1A. The current sea ice condition at this location is seasonal (0.5 to 0.7). (Stein et al., 2017)

Note that the sea ice at this location has only been seasonal since about 1,600 years ago. It was much lower than it is today for about 85% of the Holocene.

Stein et al. 2017, constructed a cross-section of PIP25 curves across the Arctic from the Fram Strait to the Chukchi Sea.

Figure 13. Location map of sediment cores and cross-section A-A’. (modified after Stein et al., 2017)

All four core locations currently reflect seasonal ice cover/ice edge situations (PIP25 index 0.5-0.7), with the Fram Strait being an ice edge situation and the other three reflecting seasonal ice cover.

Figure 14. Cross-section A-A’. High and low refer to Northern Hemisphere insolation.

Two key takeaways:

  1. Maximum Holocene sea ice extent occurred within the past 500-1,000 years at every location.
  2. The current sea ice extent is higher at all of the locations than over 50% to 85% of the Holocene.

When I plot the cross-section on Kinnard’s probability map, we can see that the entire area of low ice extent larger than present day, has been seasonal throughout most of the Holocene.

Figure 13. Stein cross-section on ice probability map.

A significant reduction in Arctic summer sea ice relative to today, would be returning to Early Holocene conditions. If we currently have an “Anthropocene in the Arctic,” it’s actually icier than most of the Holocene’s “Goldilocks conditions.”

There’s nothing to see here, move along

According to the IPCC, summer sea ice will vanish by 2070 under RCP8.5 or muddle along under RCP2.6.

Figure 15. IPCC AR-5 “future changes” under various scenarios.

The temperature data point to muddling along…

Figure 16. UAH v6.0 vs RCP’s.
Figure 17. HadCRUT4 vs RCP’s.

CONTINUE READING –>

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