Temperature and mineral dust variability recorded in two low-accumulation Alpine ice cores over the last millennium

Among ice core drilling sites in the European Alps, Colle Gnifetti (CG) is the only non-temperate glacier to offer climate records dating back at least 1000 years. This unique long-term archive is the result of an exceptionally low net accumulation driven by wind erosion and rapid annual layer thinning. However, the full exploitation of the CG time series has been hampered by considerable dating uncertainties and the seasonal summer bias in snow preservation. Using a new core drilled in 2013 we extend annual layer counting, for the first time at CG, over the last 1000 years and add additional constraints to the resulting age scale from radiocarbon dating. Based on this improved age scale, and using a multi-core approach with a neighbouring ice core, we explore the time series of stable water isotopes and the mineral dust proxies Ca2+ and insoluble particles. Also in our latest ice core we face the already known limitation to the quantitative use of the stable isotope variability based on a high and potentially non-stationary isotope/temperature sensitivity at CG. Decadal trends in Ca2+ reveal substantial agreement with instrumental temperature and are explored here as a potential site-specific supplement to the isotope-based temperature reconstruction. The observed coupling between temperature and Ca2+ trends likely results from snow preservation effects and the advection of dust-rich air masses coinciding with warm temperatures. We find that if calibrated against instrumental data, the Ca2+-based temperature reconstruction is in robust agreement with the latest proxy-based summer temperature reconstruction, including a “Little Ice Age” cold period as well as a medieval climate anomaly. Part of the medieval climate period around AD 1100–1200 clearly stands out through an increased occurrence of dust events, potentially resulting from a relative increase in meridional flow and/or dry conditions over the Mediterranean.



https://cp.copernicus.org/articles/14/21/2018/

Figure 11 which shows temperature reconstruction with a two-year resolution. Very impressive. Note the steepness of both warming and cooling trends. Dropping by 2.3C between 1190 and 1240 and increasing by the same amount 850 - 855885. So 50 years and 35 years. but somehow 1C in 150 years is "alarming".

And all this when, apparently, there was little change in CO2 levels.

I guess the "control knob" forgot.

lee wrote on Jul 25^th, 2020 at 2:41pm:


cool................

chimera wrote on Jul 27^th, 2020 at 2:23pm:



Nope. There are pieces both under and over the +1C and -1C markings.

chimera wrote on Jul 27^th, 2020 at 2:23pm:


Described by whom? Since 1979?



"In the graphical illustration of Late Holocene West Greenland sea ice changes shown above, Kolling and colleagues (2018) indicate that both present-day and Little Ice Age era (~1300s to 1800s AD) sea ice does not melt until May.(Fig. 6a).

During most of the last 2,200 years — especially during the Medieval Warm Period (MWP) and Roman Warm Period (RWP) — spring sea ice melted in March, two months earlier than today (Fig. 6b)."

https://notrickszone.com/2018/08/16/new-arctic-study-finds-spring-sea-ice-melted...

The_Barnacle wrote on Jul 27^th, 2020 at 4:16pm:



Poor petal. Perhaps you can show where I said anything different? It is just another view, with a much tighter resolution. Perhaps you thought I meant global temperatures?

The_Barnacle wrote on Jul 27^th, 2020 at 4:16pm:



What did I cherry pick petal? Please be specific. 

chimera wrote on Jul 27^th, 2020 at 5:16pm:



The faint blue line decreases from +0.8C to at least -1.5C, between 1190 and 1240. That is 2.3C.

The second date has been edited a strikethrough on 855 and changed to 885.

Between 850 and 885 it is at least 1.9C.  But I'll let you quibble the slight differences.

chimera wrote on Jul 27^th, 2020 at 5:16pm:


So nothing on your Arctic ice claim? How unusual.

Captain Nemo wrote on Jul 27^th, 2020 at 5:43pm:



And even without those uncertainty bars, far faster changes than the recent warming.