BBC News: Hocus pocus:the disappearing and reappearing Ngozumpa glacial lake

Figure 1: Time lapse video of the Ngozumpa glacial lake filling and draining over a fifteen day period (Source: Live Science, 7th December 2011).

Reflecting the general trend across the region, melting of the debris-covered Ngozumpa glacier in Nepal is of growing concern for scientists due to the rapid growth of the glacial lake at the glacier's snout. Named the 'Spillway', the glacial lake is equivalent in size to 40 Olympic swimming pools contained behind a terminal moraine dam (BBC News, 26th December, 2011). Although it is claimed the threat of a glacial lake outburst flood (GLOF) is less imminent than other glacial lakes, scientists are still monitoring changes in the dynamics of the lake. Using timelapse cameras, research by the Cooperative Institiute for Environmental Sciences (CIRES) have demonstrated dynamic fluctuations in the lake volume reflecting complex interaction of factors controlling inflow and outflow to the lake (Figure 1). Observations from the time-lapse cameras showed a decrease in volume by over 100,000m³ in two days, followed by a recovery of around half of this volume in the five days following this event (BBC News, 26th December 2011).

Although assessments of the Spillway suggest this glacial lake is less of an imminent threat to outburst compared to other glaciers in the region, the results from the timelapse videos demonstrate the complex interaction of factors controlling the growth of glacial lakes in the Himalayas. Beyond a basic understanding of the relationships between glacial lake growth and glacier melt this research highlights our limited understanding of the mechanisms regulating volume within these glacial features. Coinciding increased rates of glacial melt due to climate change, the frequency of GLOFs are increasing. Thus understanding the dynamics behind the formation and regulation of lake volume, being undertaken in studies such as this is becoming increasing important.

Reference:

Amos, J. (2011) 'Taking the pulse of Ngozumpa', BBC News, 26th December 2011. 

National Geographic Special Issue: Water Is Life

Source: Hogshon, R. National Geographic 21st December 2011).

This week the National Geographic have released a special series dedicated to the importance of freshwater for humans and global biomes around the world. Specifically related to this blog, one of the articles summaries recent research presented at the American and Geophysical Union last month (National Geographic News, 20th December 2011). Findings from different mountain ranges around the world including the Andes, Himalayas and the Canadian Rockies indicate that rates of retreat are occurring faster than previously anticipated. For example, research by the University of British Columba, Vancouver suggest in the Saint Ellias region of the Canadian Rockies glaciers could decrease to 50% of their size by 2100, of which many may even disappear completely. The article also states that global changes in glacier melt will have severe consequences on local and regional river discharge, as discussed in my last post.

The national geographic provide a variety of interactive applications including: calculating your own water footprint and visual representations that put your water use into perspective compared to other regions of the world. As our population continues to increase, trying to use our freshwater as efficiently as possible has never been more important.

In the news this week...

PAPER COMPARING THE MEDIEVAL WARM PERIOD, LITTLE ICE AGE AND THE 20TH CENTURY WARMING RATES

Using the climate system model 'FGOAL', TianJun et al., (2011) compared the differences between the rates of global warming between the Medieval Warm Period (MWP), Little Ice Age (LIA) and twentieth century. Multiple proxies were used in the model obtained from tree rings, ice cores, pollen and other records from thirty areas around the world, resulting in forcing data on volcanic events, solar insolation, nirous oxide, carbon dioxide and methane (Figure 1). Simulating changes on a global scale, the model indicated a warming during the MWP in all regions except the North Pacific. The model also demonstrated that warming was not uniform, with rates greater in the Northern hemisphere, than in the Southern hemisphere, and greater warming at higher latitudes. However, the overall warming during the MWP was not as strong as observations during the 20th century (Figure 2). During the LIA overall a global cold anomaly was observed in surface temperature, although mean surface temperature remained around +0.5° C in North-east America (although this is comparitively lower than during the MWP and 20th century anomaly).

Figure 1: Time series of forcing data used in the FGOAL model (Source Tian et al., 2011: 3084)



Figure 2: Annual mean surface air temperature anomalies for top to bottom (Medieval Warm Period, Little Ice Age and the 20th century).

Observations from the model support the concept of accelerated warming during the 20th century due to increased inputs of greenhouse gases into the atmosphere. This is evident in Figure 1, where there are significant increases in carbon dioxide, methane and nitrous oxide concentrations in the atmosphere from the Industrial Revolution in the mid-18th century, and is claimed by some (Crutzen, 2002) as the start of the 'anthropocene'.  


PALEOCLIMATIC RECORD SUGGESTS TIBETAN PLATEAU TEMPERATURES WILL DECREASE UNTIL 2068

A paper released by Lui et al., (2011) using palaeorecords from tree rings in the central-eastern Tibetan Plateau suggests that temperatures in the region will decrease until AD 2068 and will then begin to increase. Based on a 2485 year record, the tree ring record observes changes in temperature coincising with the MWP, LIA and 20th century warming, and cycles in temperature related to sunspot activity. Six cold and six warm events (half a standard deviation,±0.4°C, from the mean) were observed during the 2485-year period. Several significant cycles at 1324 year, 800 year, 190 year and 110 year were noted in the temperature series, and the cold events observed in the time-series coincided with periods of sunspot minimum. From the reconstructed temperature record, Lui et al., (2011) projects a decrease in temperature until 2068 reflecting as the earth enters a sunspot minimumn, followed by an increase in temperatures to 2088 (Figure 1).

However Lui et al.,'s (2011) study does not consider other forcings that influence global temperatures. Studies in previous posts have suggested that anthropogenic emissions of GHG's have accounted for a greater amount of the variability in global temperatures during the 20th century relative to insolation and volcanic activity. Therefore further research using multiple proxies covering a larger area is required to validate these findings. 

Figure 1: Reconstructed temperature record from a tree ring proxy in the central-eastern Tibetan Plateau over the last 2485years, and future changes projected due to sunspot variability.

Reference:

Liu, Y., Q. Cai, H. Song, Z. An and H. W. Linderholm (2011) 'Amplitudes, rates, periodicities and causes of temperature variation in the past 2485 years and future trends over the central-eastern Tibetan Plateau', Chinese Science Bulletin, 56: 2986-2994.

TianShun, Z., B. Lou, W. Man, L. Zhang and J. Zhang (2011) ' A comparison of the Medival Warm Period, Little Ice Age and 20th century warming simulated by the FGOALs climate systems model', China Science Bulletin, 56: 3028-3041.

Christmas Number One? Not quite 'I saw mummy kissing santa'!

Now here's a challenge. Making a song about glaciation. Now call me a scrudge but current Christmas songs don't seem to have any relation to Christmas or snow in them at all. So here's my contribution. I can't say I wrote it myself, and it is based on glaciation rather than Christmas so no relation to Santa, but its got snow in it so why could this not be number one? Then we could have education and festivities at the same time. Okay, so maybe I'm taking it too far, but I believe this song produced by Dan Bull on 'glaciation' provides a unique way of explaining scientific topics to a wide variety of people. Coming from someone who cannot think of a word to rhyme with glaciers, I was impressed and thought this song was worth sharing. Let me know what you think…

BBC report: Melting glaciers and changes to the River Ganges (1st November 2009)

I found this clip of a BBC report explaining how the melting Gangotri glacier (the source of the headwaters of the River Ganges) is affecting the the flow of the River Ganges and the communities that rely on the river (Figure 1). Although rather basic, it provides a brief review of the points made in my post last week about the link between melting glaciers and changes in the dynamics of rivers in the Himalayas. However, there are some overlooked generalities made in the report that are worth highlighting:

1) States that all glaciers in the Himalayas are retreating, but at different rates.

Work by Hewitt (2005) has demonstrated this statement cannot be applied to all glaciers in the Himalayas. Hewitt (2005) shows that glaciers in the Karakoram region are largely remaining static and some are advancing. This highlights the spatial complexity of glaciers within the Himalaya, and emphasises the importance of local research, as general patterns cannot be generalised across the entire region.

2) The retreat of the Gangotri glacier by 15m in 6 months.

The period of retreat described in the clip occurred during the summer months between May to October when the rates of glacier melt are at that greatest in most parts of the Himalayas. Although it visually provides a persuasive argument for the retreat of glaciers, in order to assess the significance of this rate of retreat can only be evaluated by comparison of long-term changes in the extent of the Gangotri snout.

Figure 1: Video of a BBC report on the melting Gangotri glacier and potential impacts on the River Ganges. First aired on the 1st of November in 2009 this report occurred in the weeks before the 2009 Copenhagen Summit and the release of the ClimateGate scandal where the IPCC were forced to retract their statement that all Himalayan glaciers potentially all vanishing by 2035.


Reference:
Hewitt, K. (2005) 'The Karakoram anomaly? Glacier expansion and the 'elevation effect', Karakoram Himalayas', Mountain Research and Development, 24, 4: 332-340.

In the news this week...

USAID STUDY TO ASSESS ASIAN WATER RESOURCES

United States Agency for International Development have teamed up with a University Boulder team to carry out a four year study investigating the contribution of snow and glacier melt to water resources supplied by the Himalayas. This report aims to increase our understanding of the snow and glacial input to river discharge which can then be used to predict future variability in river discharge under climate change.Due to the limited data available in the region, USAID will use a combination of remotely sensed data to produce time-series maps of intra-annual snowfall and glacial ice melt (NSIDC, 7th December, 2011). This will be combined with meterological and hydrological data in the region to estimate current relationships between snow and glacier contribution and river discharge that can then be extrapolated to predict future river discharge under differenet warming scenarios.

The findings of this study will be highly beneficial for scientists and policy makers within the regions, potentially highlighting the regions that will be at most risk under climate change allowing mitigation methods to be put in place to reduce water scarcity threat in these areas. The data could also be informed in further development schemes, such as avoiding the development of new irrigation plants in areas that are assessed at being at high risk of reductions in river discharge. As my last post has stated, changes to Himalayan glaciers is anticipated to have substantial intra-annual and longer term impacts on river discharge in the region, however, with studies like this being undertaken, our ability to understand the factors determining these changes and how they may change in the future may allow mitigation measures to be put in place to attempt to reduce their impacts.

Figure 1: Major rivers within the ten countries surrounding the Himalayas with headwaters in the mountain area (Source: NSIDC, 7th December 2011).

ICIMOD RELEASE NEW REPORTS SUGGESTING HIMALAYAN GLACIERS ARE MELTING

Following the retraction of a statement in the Fourth IPCC report that ‘all of the Himalayan glaciers would have melted by 2035’, the IPCC has announced that the most recent conclusions from three ICIMOD reports provide new evidence Himalayan glaciers are melting Compiling data from across the Hindu-Kush Himalaya (HKH) Region, these reports provide the most recent data regarding climate change for the region. However, although these reports are the most comprehensive studies yet, ICIMOD state that further research needs to be carried out (ICIMOD, 4th December, 2011)

The reports:

1) The Status of Glaciers in the Hindu-Kush Himalayan Region.

The first report used remotely sensed data to estimate the current extent and distribution of glaciers within the HKH region. Identifying approximately 54,000 glaciers within the region, the lack of data in the region is underlined as of these only ten have been continously monitored to assess changes in glacial mass. Conclusions from the remotely sensed data showed an overall reduction in glacial mass in the central and eastern Himalayas, with reductions over the last thirty years being 22% and 21% in Bhutan and Nepal respectively.

Although additional research will need to be carried out this comprehensive report provides a baseline that can be used to inform discussions over climate change within the Himalayas and can be used to direct further research in the area.

2) Snow Cover Mapping and Monitoring in the Hindu-Kush Himalayas

This report uses regional monitoring to observe changes in the HKH region over the last decade. It concludes that there has been regional disparities within the mountain chain with snow cover decreasing within the central part of the Himalayas, but monitoring indicating a slight increase within the eastern and western regions.

3) Climate Change in the Region: The State of Current Knowledge..

Reviewing the current literature available under the three broad headings: climate and hydrology; biodiversity and ecosystems; and atmospheric changes. The reports underlines the bias of the limited spatial data within the region, often restricted to areas of easier access at lower elevations. Despite this, the report identifies several conclusions within the region including:

•  More pronouced warming in the winter months than the summer months (A claim supported by Singh et al., (2006) report cited in my last post).
• The average overall warming in the region (around 0.74°C in the last 100years) is greaer than the global average, although the ICIMOD emphasis that this is not evenly distributed across the region.
• The report found that warming was most pronounced in the higher altitudinal regions such as the central Himalayas and the Tibetan Plateau, and related to the second report may partially account for the reduction in snow cover in these regions 

• Significant changes in mountain habitats are beginning to occur with the mountain treeline shifting to higher elevations, and the report suggests that some species at higher elevations may disappear as the ecosystems change.

Overall these three reports represent a significant step in bridging some of the major knowledge gaps present in this region, and highlights the benefits of using remotely sensed data when access is to the study area is limited. These reports also support the growing evidence that changes due to global warming may be exaccerbated in the Himalayan region, and therefore the continuation of studies such as this are highly important.

Up the creek without a paddle: Intra-annual and longer term changes to river discharge in the Himalayas

Continuing from last weeks post on GLOFs, this post shall review the impacts that glacier distribution and mass may have on discharge of rivers whose headwaters are situated in the Himalayas. Supporting one-third of the world’s global population (Singh  et al., 2006) changes in glacial melt will alter the discharge of these rivers on both intra-annual and also longer-term timescales.

CONTRIBUTION FROM GLACIAL MELT

It is estimated that the River Ganges is replenished by meltwater from approximately 4,000 glaciers and over 3,300 are calculated to contribute to the annual discharge of the River Indus (Thayyen and Gergan, 2010). Rees and Collins (2006) demonstrated that Himalayan glaciers contribute to both intra-annual variations in river flow and also in addition to precipitation, longer-term changes in annual river discharge. The contribution of a glacier to river flow is basin-specific with the glacial melt component comparatively higher in glacierised basins than less glacierised basin, with the latter receiving a greater contribution from surface runoff (Rees and Collins, 2006).

However, although the extent glacial coverage in the basin will undoubtedly contribute to the initial contribution, and thus subsequent change, of the glacial melt component to the river discharge, the significance of the affect of changing glacier discharge will also depend on surface runoff input by precipitation. This applies to both intra-annual and longer-term river discharge variability.

INTRA-ANNUAL VARIABILITY

Thayygen and Gergan's (2010) study of the Dokriani glacier in Garwhal, Himalaya monitored the summer variability of runoff at three hydrometric and meterological stations at different altitudes in the basin between 1998-2004 (from 3,400masl just below the glacier snout to 2,360masl in an unglacierised region further down in the valley).  Over this six-year period, summer streamflow gradually decreased from 290 x10⁶m³ in 1998 to the lowest measured discharge of 123 x 10⁶m³ in 2004 (Thayyen and Gergan, 2010). Discharge from the uppermost station, 600 metres below the glacier snout also recorded a 50% decline in discharge over the same period. However, observations at the lowest station (Tela) indicate that the glacier component to the total river discharge downstream nearly doubled, from 18% in 1998 to 34% in 2004. Thus contribution of the glacial component to river flow increased despite the actual discharge from the glacier decreasing. Comparison against precipitation values between 1998-2004 showed a fall in summer precipitation. Therefore, glacier melt was acting as a buffer against reduced surface runoff, augmenting the years of low summer flow (Thayyen and Gergan, 2010). This is an key point as it highlights the importance of glacial discharge to maintaining river discharge during low flow periods, thus supplying communities with a freshwater source when the demand is the greatest during the summer months. This is underlined by the lowest specific runoff values recorded in the study with the lowest specific yield from the glacierised catchment 15mm day^-1, 4mmday^-1 higher than the non-glacierised (precipitation-dependent) catchment (Thayyen and Gergan, 2010).

Singh et al. (2006) also demonstrated the intra-annual importance of glacier melt to river flow. Applying the SNOWMOD snowmelt model to same glacier, Dokriani, between 1997 and 1998, the model showed a linear increase in stream discharge with a rise in temperature for both of years, with glacial melt and rainfall contributing 87% and 13% respectively. The model also highlighted variation in runoff within the summer months with the largest percentage changes in runoff occurring in September and the smallest in July in 1997, whilst the reverse was recorded in 1998. Related to 1998, the highest percentage change in June (23%) attributed to a later onset of the monsoon (Singh et al., 2006). However, in the subsequent months, the impact of precipitation changes decrease and the glacial component becomes more important and thus air temperature, which influences glacial melt becomes the main factor. Using the limited duration of data available, the model projected that a 2°C rise in temperature would cause summer discharge to increase by approximately 28% (Singh et al., 2006).

LONGER TERM VARIABILITY

In addition to augmenting low flow during the summer months, changes in glacier melt will affect long-term annual discharge of rivers with headwaters in the Himalayas.

Bhutiyani et al., (2008) studied the flow of four rivers in the northwestern Himalaya from 1961-2004, with an extended study for one of the rivers, Satluj River, from 1922-2004. In the absence of specific catchment data, regional temperature and precipitation were used to analysed the changes in discharge in each of the rivers obtained from hydrographs. Initial observations from the basins showed insignificant changes in the relatively less glacierised Beas and Ravi river discharge, whilst Chenab, the most glacierised catchment showed a significant increase in discharge between 1961-2004. However, precipitation from the summer monsoon in the Beas catchment decreased, demonstrating that glacial melt is again buffering against reductions in river flow. Temperature in the northwest region of the Himalayas has being warmed by approximately 4.4°C in the winter months in the last two decade (Bhutiyani et al., 2008). This has caused an increase in glacial melt as the transient snowline increases in altitude causing greater ablation rates at the glacier snout. The short-term implications of increased glacial discharge, as observed in Beas, Ravi and Chenab is either a maintenance of river discharge as precipitation decreases or, as in the case of Chenab where precipitation was relatively constant, an increase in river flow.

Although in the short-term (four decade) period of these three rivers, glacial retreat causes a rise in stream discharge which would be beneficial to local communities, the longer term (1922-2004) study at Satluj shows a reversal of this increase in a longer time frame. Between 1922-2004 the river discharge fluctuated from above normal to below normal discharge (Bhutiyani et al., (2006). From 1945-1990 above normal discharge was observed within the Satluj river. Whilst the initial rise (1945-67) coincided with relatively static temperature changes and a rise in precipitation, the later phase (1968-90) occurred during a period of increasing temperature and a decline in monsoon precipitation suggesting glacial melt was buffering river discharge against falling surface run-off input (Bhutiyani et al., (2008). Since 1990, discharge has begun to decrease. Bhutiyani et al., (2008) argues that this decline is due to a reduction in the glacier-melt component of discharge which reached its maximum during the 1968-1990 period and has now thinned considerably. The key observations from the longer-term study suggest that in the short term, assuming precipitation remains constant, river discharge will increase. However, in the long-term once glaciers have reached a maximum, their contribution to river flow will begin to decline and subsequently river discharge will also decrease. The current observed weakening of the monsoon will only exacerbate river discharge changes further, with a reduction in flow likely to occur sooner as glacial melt is augmenting against reductions in surface runoff input. This will have significant impacts on communities within the Himalayan region, and will be expanded upon further in my next post.

REGIONAL DISPARITIES.

The complex regional climate with the Himalayas, mean the impacts of future warming on river flow will vary across the mountain chain, The glacio-hydrological regimes in the Himalaya differ related to the decrease in the influence of the monsoon from the east (monsoonal) to the drier west (Rees and Collins, 2006). Using a temperature-index based model, Rees and Collins (2006) modelled the changes in river discharge of two hypothetical catchments, one in the west and one in the east. By using hypothetical catchments, the study could maintain other parameters such as glacial coverage and basin size that could otherwise influence the response of the river to changing glacial melt rate. A baseline scenario using climate data from 1961-90 and a warming scenario of 0.0.6°C were run for a 150 year period starting from 1990. As shown in Figure 1, in the short-term river discharge increases due to rising temperatures increasing glacial melt discharge cause the hypothetical glacier to retreat. Once the rate of new ice exposed by the increasing snowline is no longer offset by the melt of the glacial ice below this line, then the glacial discharge begins to decrease indicated by a fall in river discharge (Rees and Collins, 2006). The diagram also shows that the impacts of the retreating glacier are more distinct in the drier western catchment (Figure 1a), and the initiation in the decrease is sooner and rate comparitively greater in the western catchment compared to in the east where the monsoon suppresses the changes in glacial melt.



Figure 1: Variation in annual mean flow under the 0.06°C yr^-1 warming scenario for a)the western catchment and b) the eastern catchment (Source: Rees and Collins, 2006:2166)



CONCLUSIONS

Review of some of the current literature on hydro-glaciological regimes in the Himalayas demonstrates the important contribution of glacial-melt to both intra-annual and longer-term changes in Himalayan river flow. In addition to augmenting periods of low summer flow, glacial melt also buffers against yearly variations in precipitation across the mountain chain. In the short-term, rising temperatures are anticipated to cause an increase in the glacial melt component to river discharge, with the subsequent change in short-term river discharge (remaining static or increasing) depending on the precipitation regime in that area (declining or stable/increasing). Intra-annual changes to river discharge will also depend on summer precipitation, and under the current pattern of a weakening monsoon, glacial melt is becoming increasing important in augmenting against low summer flow. If current global warming continues, in the long term it is predicted that after a peak in river discharge, discharge will subsequently begin to fall, a pattern simulated in both the east and west Himalaya. This will have significant implications for countries bordering the Himalayas, with over one-third of the world’s population currently dependent on Himalayan rivers for freshwater, and this value is growing. Therefore, changes to river discharge are of growing political and social concern and significant investment will be needed to prepare for declining river discharge in the future.   

Reference:

Bhutiyana, M. R., V. S. Kale and N. J. Pawar (2008) ‘Changing streamflow patterns in the rivers of northwestern Himalaya: Implications of global warming in the 20^th century’ Current Science, 85, 5: 618-626.

Rees, H.G. and D. N. Collins (2006) ‘Regional differences in response of flow in glacier-fed Himalayan rivers to climatics warming’, Hydrological Processes, 20, 10: 2157-2169.

Singh, P., M. Arora and N. K. Goel (2006) ‘Effect of climate change on runoff of a glacierised Himalayan basin’, Hydrological Processes, 20: 1979-1992.

Thayyen, R. J., and J. T. Gergan (2010) ‘Role of glaciers in watershed hydrology: a preliminary study of a “Himalayan catchment”, The Cryosphere, 4: 115-128.