You are currently browsing the daily archive for August 11, 2007.

Here is a mixed bag of recent papers on the Cryosphere in general. It’s not meant to be comprehensive, but illustrative of the work that has been going on, and some recent adjustments to ideas about what is going on, in particular in the oceans, and some of the mechanisms which may either influence, or be influenced by, the current state of the Arctic sea ice.

I have tried to briefly explain why this might be significant, hopefully without too many errors or misunderstandings.

This seems to be a significant finding, so we’ll start with:

Shindell, Drew

Local and remote contributions to Arctic warming

Geophys. Res. Lett., Vol. 34, No. 14, L14704


20 July 2007 [Full Article] [Print Version] [Abstract]

Concludes that: ozone and aerosols affect Arctic climate more strongly per unit global forcing than well-mixed greenhouse gases, typically 2.5–5 times in non-summer seasons, making them powerful levers for influencing Arctic climate.

Next, there is:

Jongma, J. I.; Prange, M.; Renssen, H.; Schulz, M.

Amplification of Holocene multicentennial climate forcing by mode transitions in North Atlantic overturning circulation

Geophys. Res. Lett., Vol. 34, No. 15, L15706


08 August 2007 [Full Article] [Print Version] [Abstract]

As this seems quite an interesting paper, here is the whole abstract:

Using a three-dimensional global climate model, we show that mode-transitions in North Atlantic deep-water production can provide an amplifying mechanism of relatively weak climate perturbations during the Holocene. Under pre-industrial boundary conditions, a freshwater forcing in the Labrador Sea pushes the North Atlantic overturning circulation into a deterministically bistable regime, characterized by stochastic “on” and “off” switches in Labrador Sea convection. On a multicentennial time-scale these stochastic mode-transitions can be phase-locked by a small (subthreshold) periodic freshwater forcing. The local small periodic forcing is effectively amplified with the assistance of noise, to have a large-scale impact on North Atlantic overturning circulation and climate. These results suggest a stochastic resonance mechanism that can operate under Holocene boundary conditions and indicate that changes in the three-dimensional configuration of North Atlantic deep-water formation can be an important component of multicentennial climate variability during interglacials.

Then, there’s more on the Palaeoclimate:

Hillaire-Marcel, C.; de Vernal, Anne; Piper, David J. W.

Lake Agassiz Final drainage event in the northwest North Atlantic

Geophys. Res. Lett., Vol. 34, No. 15, L15601


02 August 2007 [Full Article] [Print Version] [Abstract]

From the abstract: Proxies of sea-surface and deep-current conditions do not indicate significant concomitant changes in the NW North Atlantic. The dataset, however, supports the concept that the 8.2 ka “climate” event may represent one of the manifestations of climate instability during an interval with major changes of land drainage in NE America, due to the collapse of the Laurentide Ice Sheet, subsequent fast sea level rise and large scale reorganization of the North Atlantic thermohaline circulation pattern.

This is a bit of an oddity, but it might suggest that we can’t simplify relations between ice and circulation too much, in case the models get it wrong:

Saenko, Oleg A.; Weaver, Andrew J.; Robitaille, Daniel Y.; Flato, Gregory M.

Warming of the subpolar Atlantic triggered by freshwater discharge at the continental boundary

Geophys. Res. Lett., Vol. 34, No. 15, L15604


04 August 2007 [Full Article] [Print Version] [Abstract]

Shows a slightly contradictory picture; when freshwater influx increases, the NA surface gets warmer, if there is plenty of ice in the Labrador Sea: the postulated relationship between freshwater influx and surface temperature may well be dependent on other conditions at the time.

This one is on permafrost, supporting previous hypotheses about lake loss due to GW:

Grippa, M.; Mognard, N. M.; Le Toan, T.; Biancamaria, S.

Observations of changes in surface water over the western Siberia lowland

Geophys. Res. Lett., Vol. 34, No. 15, L15403


07 August 2007 [Full Article] [Print Version] [Abstract]

Concludes: These observations support the hypothesis that climate warming in discontinuous permafrost environments may lead to a reduction of small lakes and wetland areas.

On the Antarctic and climate change signals, this could be of some significance:

Zenk, Walter; Morozov, Eugene

Decadal warming of the coldest Antarctic Bottom Water flow through the Vema Channel

Geophys. Res. Lett., Vol. 34, No. 14, L14607


26 July 2007 [Full Article] [Print Version] [Abstract]

It concludes that the Antarctic Bottom Water flowing through the Vema Channel has been warming at a rate of 2.8 mK -1 per year since 1992.

A ‘blogmate’ writes:

Schröder, D.; Connolley, W. M.

Impact of instantaneous sea ice removal in a coupled general circulation model

Geophys. Res. Lett., Vol. 34, No. 14, L14502


19 July 2007 [Full Article] [Print Version] [Abstract]

Suggests that sea ice levels could recover fairly rapidly under the right circumstances, but more importantly, that the current models could be way out in their estimates, and need some serious work done on them.

This seemed important, because of its connection to Curry & Mauritzen’s work at Woods Hole (WHOI), which linked a circulation shift with the freshwater regime in this area:

Boessenkool, K. P.; Hall, I. R.; Elderfield, H.; Yashayaev, I.

North Atlantic climate and deep-ocean flow speed changes during the last 230 years

Geophys. Res. Lett., Vol. 34, No. 13, L13614


14 July 2007 [Full Article] [Print Version] [Abstract]

Variations in the near-bottom flow speed of Iceland-Scotland Overflow Water (ISOW) are documented in a 230-year-long deep-sea sediment record from the eastern flank of Reykjanes Ridge in the subpolar North Atlantic at (sub)decadal time scales. For recent decades, the ISOW palaeocurrent reconstructions show similarities with observational hydrographic data. Furthermore, recent ISOW flow changes fall mostly within the range of its variability of the past 230 years. The record also reveals a hitherto unrecognized coupling of deep flow speeds in the subpolar North Atlantic with the North Atlantic Oscillation (NAO) index, with more (less) vigorous ISOW flow during negative (positive) phases of the NAO. Our results suggest that the changes in ISOW vigor are largely controlled by the transport and characteristics of Labrador Sea Water rather than variations in the overflow itself, with implications for the meridional overturning of the Atlantic Ocean and climate.

Though it hasn’t yet been officially published, this is the journal I’m keeping a close eye on:


Practically every paper here has some interest, though I must admit to some perplexity about the most recent one. Perhaps something has been lost in translation.


And here is a link to the home site of the IPY. I haven’t started looking at their output or links yet, so if you want to get a jump, you can do it for yourself:


As this is already long, Comments on the implications (if any) of this and other research will follow later…


Be loved.


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August 2007