Oszillierendes Klima: Bond-Zyklen in Marokko entdeckt

Sein Name war Bond, Gerard Bond. Im Jahr 2001 veröffentlichte er zusammen mit Kollegen in Science ein Paper, dessen enormer Wert wohl erst mit einigen Jahrzehnten Verspätung von der Fachwelt voll realisiert werden wird:

Persistent Solar Influence on North Atlantic Climate During the Holocene
Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene. The evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon-14 and beryllium-10 and centennial to millennial time scale changes in proxies of drift ice measured in deep-sea sediment cores. A solar forcing mechanism therefore may underlie at least the Holocene segment of the North Atlantic’s “1500-year” cycle. The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally.

Lüning & Vahrenholt (2016) haben die Literatur intensiv nach den Bond-Zyklen durchforstet und ihren Klimaeffekt auf allen sieben Erdteilen entdecken können:

The Sun’s Role in Climate

Millennial-scale climate variability is a globally well-established Holocene phenomenon described for all oceans and continents. Cycles are known from upper, middle, and lower latitudes, encompassing all climate zones from the Arctic to the tropics. The amplitude of the observed temperature fluctuations is often more than 1°C and thus has a similar or even greater range than the warming that has occurred since the Little Ice Age. Furthermore, many of these Holocene, natural climate fluctuations show the same level of abruptness as the 20th-century warming.

A common characteristic of many of the documented millennial climate fluctuations is their good match with solar activity changes, as well as a North Atlantic climate record by Bond et al. (2001). Besides solar activity changes, internal millennial ocean cycles may have contributed to the observed climate oscillations. Both solar and internal climate system autocyclical drivers are not yet fully implemented in the current climate models, which still do not manage to reproduce the variable Holocene climate development. Yet successful hindcast capability is generally considered a prerequisite that qualifies models to be used for modeling of future climate.

This chapter reviews Holocene millennial-scale climate fluctuations as reported in 64 papers worldwide. Future research needs to attempt a detailed correlation of the existing Holocene climate curves, complemented by additional data sets filling gaps in currently poorly documented regions. A good understanding of global Holocene millennial- and centennial scale climate variability and its possible solar forcing is required as a calibration basis for a new generation of climate models that should have the objective to reliably reproduce past climate change before attempting detailed future simulations.

Im August 2018 berichteten nun Zielhofer und Kollegen über eine Bond-Zyklik im Hydroklima Marokkos:

Western Mediterranean hydro-climatic consequences of Holocene iceberg advances (Bond events)
Gerald C. Bond established a Holocene series of North Atlantic ice rafted debris events based on quartz and hematite stained grains recovered from subpolar North Atlantic marine cores. These so-called ‘Bond events’ document nine large-scale and multi-centennial North-Atlantic cooling phases that might be linked to a reduced thermohaline circulation. Regardless of the high prominence of the Holocene North Atlantic ice rafted debris record, there are critical scientific comments on the study: the Holocene Bond curve has not yet been replicated in other marine archives of the North Atlantic and there exist only very few palaeo-climatic studies that indicate all individual Bond events in their own record. Therefore, evidence for consistent hydro-climatic teleconnections between the subpolar North Atlantic and distant regions is not clear. In this context, the Western Mediterranean region reveals key hydro-climatic sites for the reconstruction of a teleconnection with the subpolar North Atlantic. In particular, variability of Western Mediterranean winter precipitation might be the result of atmosphere-ocean coupled processes in the outer-tropical North Atlantic realm.

Based on an improved Holocene δ18O record from Lake Sidi Ali (Middle Atlas, Morocco) we correlate Western Mediterranean precipitation anomalies with North Atlantic Bond events to identify a probable teleconnection between Western Mediterranean winter rains and subpolar North Atlantic cooling phases. Our data show a noticeable positive correlation between Western Mediterranean winter rain minima and Bond events during the Early Holocene and an opposite pattern during the Late Holocene. There is evidence for an enduring hydro-climatic change in the overall Atlantic atmosphere-ocean system and the response to external forcing during the Mid-Holocene. Regarding a potential climatic anomaly around 4.2ka (Bond event 3) in the Western Mediterranean, a centennial-scale winter rain maximum is generally in phase with the overall pattern of alternating ‘wet and cool’ and ‘dry and warm’ intervals during the last 5,000 years.

Bonds Entdeckung hat vermutlich eine ähnliche Bedeutung für die Klimawissenschaften, wie die Plattentektonik in der Geologie. Erst lange nach Alfred Wegeners Tod war die Fachwelt bereit, das Konzet der wandernden Kontinente anzuerkennen. Leider wird auch Gerard Bond den Durchbruch seiner Theorie nicht mehr erleben. Er starb viel zu früh im Jahr 2005 in New York.

Siehe auch unsere Beiträge “Die Plattentektonik setzt sich durch: Lehren für die Klimadebatte” und “Kontinentalverschiebung und Klimawandel: Die wundersame Wiederholung der Wissenschaftsgeschichte“.