AGW Observer (a most excellent resource on what is being published on AGW), see also Kwok & Cunningham at the bottom on loss of multi-year Arctic Sea ice:
Published last week:
Ocean transporting heat to Arctic leads to more warming
A new study has looked at Arctic warming and sea ice. The study concentrated on the ocean heat transport. The results: “Those models which transport more energy to the Arctic show a stronger future warming, in the Arctic as well as globally. Larger heat transport to the Arctic, in particular in the Barents Sea, reduces the sea ice cover in this area. More radiation is then absorbed during summer months and is radiated back to the atmosphere in winter months. This process leads to an increase in the surface temperature and therefore to a stronger polar amplification. The models which show a larger global warming agree better with the observed sea ice extent in the Arctic. In general, these models also have a higher spatial resolution.” And conclusion: “These results suggest that higher resolution and greater complexity are beneficial in simulating the processes relevant in the Arctic, and that future warming in the high northern latitudes is likely to be near the upper range of model projections, consistant with recent evidence that many climate models underestimate Arctic sea ice decline.”
Citation: Irina Mahlstein and Reto Knutti, Ocean heat transport as a cause for model uncertainty in projected Arctic warming, Journal of Climate 2010, doi: 10.1175/2010JCLI3713.1. [abstract]
Positive low-cloud feedback from CERES and ECMWF data
Eitzen and others have studied how low-altitude cloud amount changes with sea surface temperature. Their data doesn’t cover very long period, only 5 years of data from CERES and from ECMWF reanalysis. The results: “First, the low cloud amount … and the logarithm of low cloud optical depth … tend to decrease while the net cloud radiative effect … becomes less negative as SST anomalies increase.” And: “The residual positive change in net cloud radiative effect … and small changes in low cloud amount … and decrease in the logarithm of optical depth … with SST are interpreted as a positive cloud feedback, with cloud optical depth feedback being the dominant contributor.” There are some differences regionally in the feedback amount: “with the largest positive feedbacks (~4 W m−2 K−1) in the southeast and northeast Atlantic regions and a slightly negative feedback (−0.2 W m−2 K−1) in the south-central Pacific region.”
Citation: Zachary A. Eitzen, Kuan-Man Xu, and Takmeng Wong, An Estimate of Low Cloud Feedbacks from Variations of Cloud Radiative and Physical Properties with Sea Surface Temperature on Interannual Time Scales, Journal of Climate 2010, doi: 10.1175/2010JCLI3670.1. [abstract]
Whales measuring ocean temperature
This article reports narwhals measuring ocean temperature: “Fourteen narwhals were instrumented with satellite-linked time-depth-temperature recorders between 2005 and 2007.” The whales took dives and temperatures were recorded. Results: “Whale data correlated well with climatological temperature maxima; however, they were on average 0.9°C warmer ±0.6°C (P < 0.001). Furthermore, climatology data overestimated the winter surface isothermal layer thickness by 50–80 m. Our results suggest the previously documented warming in Baffin Bay has continued through 2007 and is associated with a warmer West Greenland Current in both of its constituent water masses." But really the point of this article is: “This research demonstrates the feasibility of using narwhals as ocean observation platforms in inaccessible Arctic areas where dense sea ice prevents regular oceanographic measurements and where innate site fidelity, affinity for winter pack ice, and multiple daily dives to >1700 m offer a useful opportunity to sample the area.”
Citation: Laidre, K. L., M. P. Heide-Jørgensen, W. Ermold, and M. Steele (2010), Narwhals document continued warming of southern Baffin Bay, J. Geophys. Res., 115, C10049, doi:10.1029/2009JC005820. [abstract]
Sea level spectrum shows global sea level rising
A new study has taken the spectrum of sea level variations. In addition to that: “We present a method of plotting spectral information as color, focusing on periods between 2 and 24 weeks, which shows that significant spatial variations in the spectral shape exist and contain useful dynamical information.” With this method: “For global mean sea level, the statistical error reduces to 0.1 mm/yr over 12 years, with only 2 years needed to detect a 1 mm/yr trend. We find significant regional differences in trend from the global mean. The patterns of these regional differences are indicative of a sea level trend dominated by dynamical ocean processes over this period.”
Citation: Hughes, C. W., and S. D. P. Williams (2010), The color of sea level: Importance of spatial variations in spectral shape for assessing the significance of trends, J. Geophys. Res., 115, C10048, doi:10.1029/2010JC006102. [abstract]
Cryo-hydrologic warming making it easier for Greenland to melt
Cryo-hydrologic (CH) warming means that the melt-water in the surface of the ice-sheet warms the ice which then of course melts some more. A new study has used a thermal model of ice sheets including the CH-warming to research the situation. The CH-warming does wonders to the timescales of the ice-sheet melt: “The corresponding time-scale of thermal response is of the order of years-decades, in contrast to conventional estimates of thermal response time-scales based on vertical conduction through ice (∼10^2–3 m thick), which are of the order of centuries to millennia.” That doesn’t sound very promising. Is it occurring yet? Yep: “We show that CH warming is already occurring along the west coast of Greenland. Increased temperatures resulting from CH warming will reduce ice viscosity and thus contribute to faster ice flow.”
Citation: Phillips, T., H. Rajaram, and K. Steffen (2010), Cryo-hydrologic warming: A potential mechanism for rapid thermal response of ice sheets, Geophys. Res. Lett., 37, L20503, doi:10.1029/2010GL044397. [abstract]
Rapid climate change lessons from the past
Rapid climate changes have occurred in the past, as can be seen in the geological record. The journal Global and Planetary Change is publishing a special issue on the rapid climate changes. The introduction paper has now been published and the abstract says: “Rapid climate changes are known to have occurred over time periods equal to or even less than a human lifespan: moreover, their impacts on the global system are sufficiently large to have had significant societal impacts.” We currently seem to be facing a rapid climate change, so the knowledge of rapid climate changes in the past is important. The introductory paper gives an overview of the papers in the special issue. The overall conclusion is: “The results confirm the importance of freshwater forcing in triggering changes in Atlantic Meridional Overturning Circulation (MOC) and the close links between MOC and rapid climate change.”
Citation: Jonathan Holmes, John Lowe, Eric Wolff, and Meric Srokosz, Rapid climate change: Lessons from the recent geological past, Global and Planetary Change, doi:10.1016/j.gloplacha.2010.10.005. [abstract]
Northern Annular Mode causes uncertainties to future northern climate
The Northern Annular Mode (NAM) is a variability in the atmosphere that has an effect to climate in Northern Hemisphere. NAM is expected to change with increasing greenhouse effect. The changes in NAM are not known very well, the climate models give different kinds of responses to greenhouse forcing. A new study has looked how much uncertainty NAM introduces to northern regional climate. That was estimated from the spread of different model results. The result: “We show that the intermodel spread of the future NAM projections account for up to 40% of the variance of the surface temperature and precipitation projections over some regions in Eurasia and North America across the simulations. This result implies that the uncertainty in the future NAM makes a considerable contribution into the overall uncertainty in regional climate predictions.”
Citation: Karpechko, A. Yu. (2010), Uncertainties in future climate attributable to uncertainties in future Northern Annular Mode trend, Geophys. Res. Lett., 37, L20702, doi:10.1029/2010GL044717. [abstract]
Pine Island Glacier contribution to sea level less than 3 cm
Pine Island Glacier (PIG) in Antarctica might contribute considerably to the global sea level rise as PIG is losing mass rapidly. A new study has created a model for studying that contribution. The reasons for mass loss are discussed: “While oceanic melt likely played the leading role in recent thinning and retreat, we find that the particular grounding-line geometry with an extended ice plain in the 1990s made it susceptible to such forcing. Our model further indicates that while the rate of grounding-line retreat should diminish soon, the glacier’s mass loss may continue at rates similar to, or moderately elevated from, the present.” Then on the rate of mass loss: “While substantial, our model-derived maximum rate of 2.7 cm/century is considerably smaller than previous heuristically-derived bounds on the sea-level contribution.”
Citation: Joughin, I., B. E. Smith, and D. M. Holland (2010), Sensitivity of 21st century sea level to ocean-induced thinning of Pine Island Glacier, Antarctica, Geophys. Res. Lett., 37, L20502, doi:10.1029/2010GL044819. [abstract]
Measuring the heat flux to the oceans
The net air–sea surface heat flux has been measured in North Pacific and North Atlantic between 1984 and 2004. It turns out that the net heat flux is going into the oceans in most of the measured areas. Both in the areas of heat flux going into the oceans and in the areas of heat flux going into the atmosphere the underlying causes can be traced to the global warming.
Citation: Gen Li, Baohua Ren, Jianqiu Zheng and Chengyun Yang, Net air–sea surface heat flux during 1984–2004 over the North Pacific and North Atlantic oceans (10°N–50°N): annual mean climatology and trend, 2010, Theoretical and Applied Climatology, DOI: 10.1007/s00704-010-0351-2. [abstract]
Biodiversity suffers in Europe with climate change
A new study has used environmental and climate models to estimate stable area of species and species turnover. Climate change will have remarkable effects: “We show that if global temperature increases, then both species turnover will increase, and mean stable area of species will decrease in all biomes. The most dramatic changes will occur in Northern Europe, where more than 35% of the species composition in 2100 will be new for that region, and in Southern Europe, where up to 25% of the species now present will have disappeared under the climatic circumstances forecasted for 2100.”
Citation: Rob Alkemade, Michel Bakkenes and Bas Eickhout, Towards a general relationship between climate change and biodiversity: an example for plant species in Europe, Regional Environmental Change, DOI: 10.1007/s10113-010-0161-1. [abstract]
Review article on global drought situation
Apparently there are some original research in this work as well. I don’t need to say much about this as there is a press release on this from UCAR.
Citation: Aiguo Dai, Drought under global warming: a review, Wiley Interdisciplinary Reviews: Climate Change, 2010, DOI: 10.1002/wcc.81. [abstract, full text]
Multiyear ice melting rapidly in the Beaufort Sea
New study by Kwok & Cunningham has made estimates on the multiyear ice trends in Beaufort Sea: “For the summers of 1993 through 2009, we estimate the loss of multiyear sea ice (MYI) area in the Beaufort Sea due to melt.” The loss of area was: “Net loss of area (with fractional MYI coverage >50%) over the 17-year period is ∼900 × 103 km2. Three-quarters of that area, ∼10% of the area of the Arctic Ocean, was lost after 2000.” (The “∼” is most likely a “~”.) Rest of the abstract is worth quoting as well: “There is a clear positive trend in the record, with a distinct peak of 213 × 103 km2 in 2008; this is twice the summer outflow at the Fram Strait that year. The net melt area of 490 × 103 km2 between 2005 and 2008 accounts for nearly 32% of the net loss of 1.54 × 106 km2 of Arctic Ocean MYI coverage over the same period. Volume loss, for the years with ICESat thickness (2004–2009), is highest at 473 km3 in 2008 followed by 320 km3 in 2007. Net loss in MYI volume for the six summers is ∼1400 km3. This is ∼20% of the loss in MYI volume of 6300 km3 during 2004–2008. This adds to the freshwater content of the Arctic Ocean and locally to the freshening of the Beaufort Gyre.”
Citation: Kwok, R., and G. F. Cunningham (2010), Contribution of melt in the Beaufort Sea to the decline in Arctic multiyear sea ice coverage: 1993–2009, Geophys. Res. Lett., 37, L20501, doi:10.1029/2010GL044678. [abstract]
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