Solar forcing as an important trigger for West Greenland sea-ice variability over the last millennium

Posted: December 7, 2015 by tallbloke in Natural Variation, sea ice, Solar physics
Tags: ,

H/T to Andrew for alerting me to this new paper published in Quaternary Science Reviews.

From the paper:

14C-greenland-sea-ice

Fig. 5. Reconstructed sea-ice concentrations from core GA306-GC4 compared to the 14C production rate corrected for the fossil fuel (Suess) effect for the period from 1850 to 1950 AD (Muscheler et al., 2007). (a) The direct comparison of sea-ice concentration (blue) and 14C production rate (red), as well as with DTSI (orange; difference of total solar irradiance from 1365.57 W/m2 ) (Steinhilber et al., 2012)

To investigate the feedback processes linking solar activity and sea-ice cover, we used the coupled climate model COSMOS, which indicates that a decrease in solar radiation results in increased sea-ice cover (Fig. 7a) and decreased sea-surface temperature (Fig. 7b). A strong negative correlation between sea-ice variability and solar forcing is observed along the eastern and southwestern coast of Greenland and in the Arctic Ocean, indicating that in this model solar variability is critical for simulating changes in local sea-ice production. A small change in incoming shortwave radiation, and associated ice-albedo effects, resulted in a large response of local ice formation, according to ‘bottom-up’ (solar heating of the sea surface) mechanisms (Gray et al., 2010; Hunke et al., 2010).

In addition, the significant 216-year period is similar to the well known de Vries solar cycle of ~210 years, while the periodicity of 26 years may be related to the periodicity of the 22-year Hale cycle (Fig. 4). We note, however, that the latter periodicity (~26 years) lies close to the Nyquist period and therefore may be an artefact of the sampling frequency. Notably, the 56-year cycle in our sea-ice record is not associated with any well-known solar cycles, but falls within the range of the 55e70 year spectrum calculated for the Atlantic Multidecadal Oscillation (AMO) over the last 8000 years (Knudsen et al., 2011), although the sea-ice variability linked to solar forcing may also have impacted the AMO cycle (Knudsen et al., 2014).

 

Comments
  1. J Martin says:

    Presumably carbon 14 is s proxy for UV. Looks like there are some other components needed to get a better match.

  2. ren says:

    Abstract

    The climatic mechanisms driving the shift from the Medieval Warm Period (MWP) to the Little Ice Age (LIA) in the North Atlantic region are debated. We use cosmogenic beryllium-10 dating to develop a moraine chronology with century-scale resolution over the last millennium and show that alpine glaciers in Baffin Island and western Greenland were at or near their maximum LIA configurations during the proposed general timing of the MWP. Complimentary paleoclimate proxy data suggest that the western North Atlantic region remained cool, whereas the eastern North Atlantic region was comparatively warmer during the MWP—a dipole pattern compatible with a persistent positive phase of the North Atlantic Oscillation. These results demonstrate that over the last millennium, glaciers approached their eventual LIA maxima before what is considered the classic LIA in the Northern Hemisphere. Furthermore, a relatively cool western North Atlantic region during the MWP has implications for understanding Norse migration patterns during the MWP. Our results, paired with other regional climate records, point to nonclimatic factors as contributing to the Norse exodus from the western North Atlantic region.

    Fig. 3
    Climate records across the North Atlantic region.
    (A) Summed probability of radiocarbon ages from Baffin Island marking the last period of plant growth and the onset of regional snowline lowering (5). (B) Summed probability of 10Be ages from each moraine in the Naqsaq valley with the mean age and SD (fig. S2). Also shown are the dated moraines in Ayr Lake (AYR) and the proximal moraine in Uigordleq Lake valley (UIGP). (C) Summed probability of radiocarbon ages from the Cumberland Peninsula on southern Baffin Island (64). (D) Summit Greenland δ15N-δ40Ar gas-derived temperatures (37). (E) Alkenone-based lake temperatures in western Greenland (38). (F) Alkenone-based SSTs of the Labrador Current (35). (G) Reconstructed NAO index (6). (H) Alkenone-based SSTs off northern Iceland (35). (I) Varve thickness record from proglacial lake Hvítárvatn, Iceland (40). Increasing varve thickness represents increasing glacier size. (J) Glacier extent in the Swiss Alps (19).
    http://advances.sciencemag.org/content/1/11/e1500806.full

  3. The figure you show (numbered 5) displays a range of not much more than 0.9 Wm-2 which may be interpreted as radiative imbalance.

    James Hansen of NASA used ocean heat content among other variables to derive his estimate of radiative imbalance. In 2011 Hansen and others revised their 2005 estimate of global energy imbalance from 0.85 Wm-2 to 0.58 Wm-2 based on later data. Nir Shaviv used a variation on this approach to ocean heat content.

    Loeb et al and Stephens et al. accepted Hansen’s estimates but for more recent years they revised his figure to 0.5 Wm-2. This appears consistent with the graphs you provide in your comment: the positive global energy imbalance seems to have been falling for a couple of decades.

    Steinhilber and others estimated that there has been an increase of 0.9 Watts per square meter in solar power since the Maunder Minimum 400 years ago. This suggests that the increase in solar power since the Maunder Minimum is 80% greater than the total radiative imbalance derived from ocean heat content in 2012. That implies the radiative imbalance was negative for much of the period between about 1600 and 1850, which would explain the Little Ice Age. The decline in solar activity probably began before 1300.

    I would not claim that all of the warming during the last 400 years has been caused by the Sun, but it does appear that the increase in solar activity can explain most of the global warming. If we merely applied Occam’s Razor, we would ignore greenhouse gases, except water vapor.

    While we cannot be certain about any of these claims, we can see that natural factors may be more important as drivers of climate change than is being recognized by governments worldwide when they allocate funding for scientific research.

    References:
    1.Steinhilber, F., J. Beer, and C. Fröhlich. “Total solar irradiance during the Holocene.” Geophysical
    Research Letters 36.19 (2009).
    2.Hansen, James, et al. “Earth’s energy imbalance and implications.”Atmospheric Chemistry and Physics 11.24 (2011): 13421-13449.
    3.Loeb, Norman G., et al. “Observed changes in top-of-the-atmosphere radiation and upper-ocean heating consistent within uncertainty.” Nature Geoscience 5.2 (2012): 110-113.
    4.Stephens, Graeme L., et al. “An update on Earth’s energy balance in light of the latest global observations.” Nature Geoscience 5.10 (2012): 691-696.
    5. Shaviv, Nir J. “Using the oceans as a calorimeter to quantify the solar radiative forcing.” Journal of Geophysical Research: Space Physics (1978–2012)113.A11 (2008).

  4. oldbrew says:

    ‘Notably, the 56-year cycle in our sea-ice record is not associated with any well-known solar cycles’

    But is close to 3 lunar nodal cycles = 55.84~ years.

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