Measuring the Rise and Fall of New Zealand’s Small and Medium Glaciers

Resulting from an unprecedented marine heatwave, the nationwide average temperature in New Zealand for the record-breaking summer of 2017-2018 was 18.1oC, over 2oC above average. Sea surface temperatures varied from 2-4oC above average and even reached 6-7oC above in some areas, the highest temperature anomalies in the world at the time. More, small and medium-sized glaciers in New Zealand’s Southern Alps lost over 13 percent of their total ice volume.

The Southern Alps mountain range, which cuts diagonally across New Zealand’s South Island, is home to over 3,000 small and medium-sized glaciers, which respond to climatic changes––both anthropogenic and natural––much faster than large glaciers. Since the last Little Ice Age ended in 1860, these glaciers in the Southern Alps have notably receded, save for four periods of advancement: around 1950, 1980-1987, 1991-1997, and 2004-2008.

Aerial view of the Southern Alps, New Zealand (Source: Tim Williams/Flickr).

In a new study, published in the International Journal of Climatology, lead researcher Michael J. Salinger of Pennsylvania State University and his co-researchers provide new estimates of glacier ice volume changes and the impact of climate variability on New Zealand’s small and medium-sized glaciers. From 1977 to 2018, the total ice volume of small and medium glaciers went from 26.6 to 17.9 cubic kilometers, a 33 percent decrease.

The researchers utilized a 42-year set of measurements––an annual measurement of the altitude of the end-of-summer-snowline (EOSS)––from 1977 to 2018 to calculate the ice volume changes for a sample of 50 glaciers in the Southern Alps. The EOSS is the boundary between the current year’s new, clean snow and older, dirty snow and is measured in mid to late March, which is the end of New Zealand’s snowy season.

If a particular year experiences lots of melting, the snow line rises in elevation, whereas if snow accumulation exceeds ablation, the snow line will move down. “It’s like doing your annual budget reconciliation,” said Salinger. “So on the 31st of March, [you are] working out whether you’ve received more or less income.”

When researcher and co-author Trevor Chinn started the EOSS monitoring program in 1977, Chinn calculated the volume for all of the over 3,000 glaciers he had mapped. Salinger explained that for this study, the researchers looked at current EOSS elevation compared to years past, using that information to work out the area lost or gained, then convert that to volume of water. “I can work out the glacier contribution from sea level rise, and what I’ve found is that it has been much higher than expected,” he noted.

Valley at an entrance to the snow-covered mountains of the Southern Alps (Source: Richard/Flickr).

Natural climate variability was a primary contributor to interannual fluctuations in glacier ice volume during this time period, even though anthropogenic warming is ultimately responsible for the accelerating downward trend. Volume gains in the 1980s and 1990s were offset and quickly surpassed by rapidly accelerating ice loss from 1998-2018.

The primarily land-covered mid-latitudes of the Northern Hemisphere are much different compared to the mostly ocean-covered midlatitudes of the Southern Hemisphere, which results in strong westerly winds. Salinger cited the Southern Annular Mode (SAM) as the most important source of variability in the Southern Hemisphere. “You can think of the [SAM] as squeezing and relaxing of the westerlies, or the Roaring Forties and Furious Fifties as we call them, over the Southern Ocean,” said Salinger.

In its negative phase, the SAM produces enhanced westerlies, cooler weather, and storm activity. In the positive phase, the strong westerlies move south while westerlies in the mid-latitudes weaken, and the weather gets warmer.

“Temperatures go up and you get less precipitation producing weather and more rain than snow precipitation,” said Salinger. The SAM usually fluctuates between positive and negative phases over weeks to months, but in response to anthropogenic warming, it is becoming increasingly positive.

Salinger noted that to a lesser extent, the El Niño Southern Oscillation also causes interannual climate variability in New Zealand. During an El Niño event, the equatorial easterly trade winds are subject to westerly wind anomalies, which would enhance the negative phase of SAM, leading to even cooler temperatures. La Niña pulls the trade winds in the opposite direction, further weakening westerlies over New Zealand and contributing to more warming.

As anthropogenic warming intensified over the last century, glaciers all around the world retreated, losing ice volume, and contributing to sea level rise. At the same time, natural climate variations happening on interannual and decadal timescales also worked to temporarily offset this massive retreat, even contributing to periodic glacier advances for small and medium-sized glaciers in New Zealand. Ultimately though, glaciers are driven primarily by temperature, and so the impacts of the global warming trend will prevail.

Fox Glacier in the Southern Alps of New Zealand (Source: CameliaTWU/Flickr).

Changing glacier ice volumes throughout New Zealand pose great risks to the country, which relies heavily on hydropower for energy production and on tourism and agriculture for economic output. Salinger cited recent agricultural droughts on the South Island, and the mounting problems faced by farmers without access to irrigation on tap.

Interestingly, New Zealand uses the visual of their rapidly retreating glaciers as an opportunity to raise awareness about climate change. “Our glaciers are iconic, and people are not too far from them, so they are very familiar with them. They’ve seen the huge retreat of some of the glaciers up valleys with melting, because of global warming. It’s something tangible and people can see the long-term change,” said Salinger. “So that’s why we find our glaciers as sort of the canary in the coal mine.”

Read more on GlacierHub:

Photo Friday: New Zealand’s Glacier Retreat from Space

The Curious Case of New Zealand’s Shrinking Glaciers

What the Newest Global Glacier-Volume Estimate Means for High Mountain Asia


A Lake in Bolivia Dries Up

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Boats on the dry bed of Lake Poopó (source: D. Hoffmann)

In December 2015, while the world’s eyes were on the UN Climate Conference in Paris, Bolivia’s Lake Poopó—once the country’s second-largest lake, with an area of 2700 square kilometers–dried up completely. This event was first recognized by the regional government, located in Oruro, and soon drew national and international concern. This attention has opened a discussion on the causes of this event and on the troubling possibility that the lake may never return to its earlier size.

Some people, like Bolivian President Evo Morales, were quick to attribute the drying of Lake Poopó to natural cycles, pointing out that the lake had previously dried out, but always recovered. But others claim that climate change has played a role that will continue into the future, and also note the negative impact of human activities–irrigation schemes and mining activities–which are very unlikely to end.  

Map of the Poopó basin, with Lake
Map of the region. Lake Poopó immediately below the city of Oruro (source: Sayri)

Based on available documentation and a field visit earlier this month,  we are now in a position to share some preliminary conclusions on what happened to Lake Poopó, as well as to the perspectives for its recovery.

The current sharp decline is due most immediately to the strong El Niño event of 2015-16, which has greatly reduced rainfall in the November-March wet season, now reaching its final weeks. But the problem is rooted in long-term processes, which will not be reversed when the current El Niño event ends, most likely later this year.

The Physical Environment of Lake Poopó

Lake Poopó, like all other lakes, can be characterized by what limnologists–fresh-water ecologists–call a “water balance,” the relation between the water that enters the lake, and the water that leaves it. If unimpeded, a negative water balance will lead to the drying up of a lake. The water balance of Lake Poopó is influenced by its location in a semi-arid area (the average annual precipitation is about 370 mm) and its shallowness (the greatest depth is only 2.4 m).

Sajama, a glaciated peak in the Lake Poopó basin (source: D. Hoffmann)
Sajama, a glaciated peak in the Lake Poopó basin (source: D. Hoffmann)

Historically, Lake Poopó receives around two thirds of its water from a sole source, the Río Desaguadero; the remaining third comes from smaller rivers that flow directly into the lake and from rainfall onto the lake’s surface. The Río Desaguadero originates in Lake Titicaca, a large lake that straddles the border between Bolivia and Peru. As this river flows towards Poopó, it receives water from other tributaries, particularly the Río Mauri, an international river whose sources lie in Peru and Chile. Lake Titicaca and the other tributaries of Río Desaguadero receive water from rainfall, snowmelt and runoff from the glaciers on the cordilleras that ring the entire Titicaca-Poopó basin.

These sources provide Lake Poopó with water inputs that fluctuate from year to year, reflecting variations in the precipitation that the region receives. A set of locks that were constructed on Lake Titicaca in 2001 could permit the Binational Commission charged with managing the lake to release more water to the Río Desaguadero in dry years, but this possibility has never been realized and, given the water scarcity on the Peruvian side of the Titicaca basin, it seems very unlikely.     

Group interviewing fishermen at the dry bed of Lake Poopó (source: D. Hoffman)
Group interviewing fishermen at the dry bed of Lake Poopó (source: D. Hoffmann)

Local residents report a decrease in rainfall over the last 10-15 years, a pattern that is confirmed by data from weather stations for the last few decades and by tree-ring records that track rainfall over several centuries. Moreover, glacier retreat has diminished the contribution of meltwater to the lake–a valuable component of the water budget, since it historically compensated in part for the scanty rainfall in dry years. Bolivia has lost about half of its glacier area in the last 40 years, with particularly rapid retreat in the eastern portions of the Titicaca-Poopó basin, where the largest glaciers are located.  

Moreover, climate change affects another component of the lake’s water budget: its losses. Higher temperatures lead directly to higher evaporation rates, a significant effect in this extremely shallow body of water.  

Human Activities Impact Lake Poopó

In addition to these physical factors, human activities have reduced the water input into the lake. These activities begin far away, since new irrigation facilities draw from rivers on the Peruvian side of the basin, diverting water away from it.

In the last 10 years, new irrigation systems for small farmers have been built closer to the lake as well. During our trip around and onto Lake Poopó, we saw a large number of canals, many of them of makeshift construction, which  divert water from the Río Desaguadero for agricultural purposes. According to Eduardo Ortíz, the Oruro regional government’s director for watershed management, there are around 250 irrigation schemes legally established on the Río Desaguadero. Other experts estimate that the total number of irrigation projects is closer to 1,000, suggesting that many of them lack legal authorization. Further down its course, the Río Desaguadero was entirely dry. When we came to the former shores of the lake, we found many small villages half-abandoned, especially on the western side of the lake. The final concern is the deterioration of water quality in the lake because of contamination from nearby mines at Huanuni and other site. Salts containing lead, cadmium, arsenic and other heavy metals leach into the lake. Local communities have protested this pollution in recent years. These toxic substances become concentrated in periods of low lake levels, and could affect the restoration of lake ecosystems even in years of heavier rainfall.

Dried bed of Lake Poopó (source: D. Hoffman)
Dried bed of Lake Poopó (source: D. Hoffmann)

The drying of the lake has led hundreds of fishermen to lose their source of income, accelerating migration by the local population to urban areas.  Antenor Rojas Flores, a local fisherman from the village of Untavi in his late 50s, has begun to work as a laborer in construction in the nearby city of Oruro to support his family. He says that he hopes that water and fish will return, so that he can go back to his life as it was before, but “only God knows” whether that will happen.  

The decline of fishing has also impacted the commercial activities of women, many of whom have participated in local and regional markets. These people are members of the indigenous Uru Murato, an ethnic group with ancient roots in the region. Their livelihoods have always centered on the water, and the drying of the lake is threatening their continuity as a community; the barter relations with neighboring agricultural and pastoral communities, which supported them during dry spells in earlier historical periods, have weakened as these communities also face climate change and other pressures.

Worrying Perspectives for Lake Poopó

This set of circumstances leads to a bleak outlook for the lake. Its full recovery seems rather unlikely. The strong El Niño event of 1991-92, followed by a weaker event in 1994-95, led the lake to dry up as well; in the decades since then, it recovered neither  its full size nor its full potential in terms of productivity and biodiversity. Historic lake sizes ranged between 2,500 and 2,700 square kilometers; for the current century it has been closer to 1,500 square kilometers, reflecting the impacts of climate change on evaporation and on glacier retreat. The irrigation facilities are likely to continue to divert water. It would take strong political will to reallocate water extensively throughout the international Titicaca-Poopó basin to bring the lake back to even a semblance of its state in the last century.

Dirk Hoffmann is a researcher with the La Paz based Bolivian Mountain Institute – BMI and can be contacted at: dirk.hoffmann@bolivian-mountains.org

Climate Variability Shapes Glacier Retreat in Peru and Norway

Two recent studies, one in Peru and the other in Norway, link glacier retreat, not to climate change as many researchers have done, but to climate variability—the fluctuations in temperature and precipitation across large regions of the world, on time scales of years or decades. These studies add an important level of detail to the role of glacier science in building awareness of climate change. On the one hand, glaciers around the world are shrinking, and rising temperatures, due to the growth of greenhouse gas emissions, are the principal cause of this decline. On the other hand, glaciers do not respond uniformly and homogenously to greenhouse gas concentration and to global mean temperatures; instead, their dynamics are more varied. Indeed, one of the studies shows that some glaciers have periods of growth lasting several years, even though longer-term research indicates that they are shrinking when they are examined on a time scale of decades. The other study shows that even in an area of steady glacier retreat, there can be months with slight growth, though there are no years of net glacier growth.

These two studies are striking, because they examine glaciers which are located in different continents, at different latitudes, and in proximity to different oceans. Moreover, they use different methods, indicating the variety of techniques in glaciology. However, they both point to the influence of major patterns of climate variability on glacier dynamics.

Glacier in the Cordillera Blanca (source: University of Innsburck)
Glacier in the Cordillera Blanca (source: University of Innsburck)

In the study of a Peruvian glacier, published recently in The Cryosphere, Fabien  Maussion and his coauthors, all at the University of Innsbruck in Austria, used detailed weather data and glacier mass balance to study the Shallap Glacier in the Cordillera Blanca, a region known to have a strong influence of El Niño.  For their study period of 2006-2009, they obtained monthly data on the glacier mass balance, on the energy balance at the surface (including  incoming and outgoing shortwave and longwave radiation and  heat fluxes) and on a number of meteorological variables (temperature, precipitation, cloud cover, relative humidity, air pressure, wind speed and wind direction).  They assessed the mass balance through the use of ablation stakes. They linked these variables to each other and to  the El Niño/Southern Oscillation (ENSO), a major form of climate variability in the tropical Pacific. To assess the state of ENSO, they used a standard measure, the anomalies of the sea surface temperatures in a region of the western tropical Pacific, close to the Cordillera Blanca. (This ocean variabilility is the El Niño component of ENSO; there is also an atmospheric component, the Southern Oscillation, which is tied to the difference in atmospheric pressure between Darwin, Australia, where pressure is typically low, and Tahiti, where it is usually high. Since the ocean and atmospheric components of the variability in the tropical Pacific are highly correlated, the researchers used only the ocean component.)

Monthly mass balance of Shallap Glacier, calculated from modeling. Period of field data shown between green bars. Black line indicates calculated trend, with gray showing confidence intervals. Note greater rate of shrinking in El Niño periods, with some months of slight growth during La Niña periods. (source: The Cryosphere)
Monthly mass balance of Shallap Glacier, calculated from modeling. Period of field data shown between green bars. Black line indicates calculated trend, with gray showing confidence intervals. Note greater rate of shrinking in El Niño periods, with some months of slight growth during La Niña periods. (source: The Cryosphere)

As shown in the figure above, during the drier, warmer El Niño periods, the Shallap Glacier lost mass more rapidly. In the moister, cooler La Niña periods, the loss was slower, and there were a few months of gain, though there were no years of net growth.

In the study of Norwegian glaciers, also published recently in The Cryosphere, Mathias Trachsel and Atle Nesje of the University of Bergen used statistical methods to link three datasets. The first consists of mass balance data for eight Norwegian glaciers, some closer to the ocean and others further inland. The mass balance data begins between 1946 and 1970, depending on the specific glacier, and extends to 2010. It includes both seasonal mass balance (winter, summer) and total annual mass balance. The second is the weather data for the glaciers for the period for which mass balance data is available. The third is  climate data for two major forms of climate variability, the North Atlantic Oscillation (NAO) and the Atlantic Multidecadal Oscillation (AMO).  The NAO is an atmospheric phenomenon which reflects the variation of two major weather systems, the high-pressure system centered over the Azores and the Icelandic low-pressure system. The NAO is positive when the two systems are both relatively strong, and negative when they are weak. A positive NAO strengthens westerly winds and brings winter storms to northern and central Europe; a negative NAO sends the storms further south.  The AMO reflects the variability of the temperature of the surface waters in the North Atlantic Ocean. It is positive when these waters are warmer than normal, and negative when they are cooler.  The AMO is associated with precipitation variability across parts of North America, Europe and Africa.  These atmospheric and oceanic systems in the North Atlantic are less tightly linked that El Niño and the Southern Oscillation in the tropical Pacific, so these researchers considered them separately.

Rembesdalsskaka Glacier, one of the 8 study glaciers (source:NVE)
Rembesdalsskaka Glacier, one of the 8 study glaciers (source: NVE)

The researchers found that variability in winter precipitation had a strong influence on the mass balance of maritime glaciers, where annual temperature variability is relatively low, because of the proximity to the ocean. For the continental glaciers further inland, variability in summer temperature had a stronger influence, with greater loss during the warmer summers. These precipitation and temperature variations are associated with the NAO and AMO.

The AMO was negative for a long period, between 1963 and 1996, and this was a period of cooler than normal summers. The NAO was positive, bringing mild, wet winters, for a portion of this time, between 1987 and 1995. This period in the late 1980s and early 1990s was a time of positive mass balance, so the glaciers grew in size—a difference from Peru, where the glaciers shrank every year during the study period, though their rate of change also varied from year to year.

Net glacier growth for 8 Norwegian glaciers [top] and climate variability [bottom] (source: The Cryosphere)
Net glacier growth for 8 Norwegian glaciers [top] and climate variability [bottom] (source: The Cryosphere)
This association is important, because it shows that a general trend towards glacier retreat, caused by global warming, can be masked for a time by climate variability. None of the eight glaciers in the study have grown  since the mid-1990s (six have shrunk, and two are the same). However, four of them grew considerably in the period of favorable conditions, so they are larger than they were at the start of the research. The figure in the paper, included here, shows that two had significant net growth and remain steady, while two have lost much of their growth in this period; four of them have grown smaller, though the pace of retreat has varied.

All of these glaciers are highly sensitive to climate variability, since they are relatively warm (in Peru because of the tropical location, in Norway because of the moderating influence of the Gulf Stream); in colder glaciers, net accumulation of snow is relatively slow (because cold air does not hold as much water vapor that can form into precipitation) and net ablation or loss of ice is also slow.  The steepness of the mountain ranges in both areas may also contribute to the sensitivity to climate variability, because the ice that forms during a few years of favorable conditions will flow downslope more quickly, where it will be exposed to warmer conditions, where it will melt; glaciers in areas of gentler slopes take longer to respond, so their processes of growth will smooth out the variability from year to year or month or month—much as a small swimming pool will grow warmer or cooler as weather changes  at a more noticeable rate than a large lake.

Nonetheless, these studies show the importance of including climate variability as well as climate change in the study of glacier dynamics. Climate change skeptics were quick to pounce on a short period of glacier growth in Norway to challenge the overall global patterns of glacier retreat. Though there have been fewer claims in the last five years of such growth, these studies show the importance of offering more detailed, nuanced accounts of glacier processes. Such information is also of importance to water managers and to local communities.

El Niño is Melting Glaciers, Flooding California

Recent research has suggested an increasingly important role between the pacific decadal oscillation (PDO) and the El Niño Southern Oscillation (ENSO) on natural phenomena around the globe, including glacial melt variability. These relationships are particularly strong when the PDO and ENSO are in-phase, as they are now.

One study by Bijeesh Kozhikkodan Veettilab, Nilceia Bianchinic, Ulisses Franz Bremerab, Éder Leandro Bayer Maierd, and Jefferson Cardia Simõesa looked at the formation of supraglacial lakes on the Baltoro Glacier in the Pakistani Himalayas from 1978 to 2014. Using a combination of various satellite images the study demonstrated that most of the lakes formed or expanded during the late 1970s to 2008, and that after 2008 the number and size of the lakes decreased.

They discovered that, “the formation and expansion of glacial lakes occurred during the warm regime of PDO, in particular in phase with the ENSO,” and that the shift in 2008 corresponded precisely with the onset of a cool phase of the PDO.

Image of the PDO phases.
PDO warm and cool phases from University of Alaska-Fairbanks Physics Department

The PDO is primarily a sea surface temperature phenomenon that oscillates in the Pacific Ocean, usually switching from a warm or positive phase to a cool or negative phase every 20-30 years. In the positive phase the Eastern Pacific, along the West coast of the Americas is unusually warm, while the Western Pacific along the East coast of Asia is unusually cool. During the negative phase the opposite occurs.

The PDO is often described as a long lasting ENSO-like event. ENSO is what is commonly referred to as El Niño and La Niña, a sea surface temperature oscillation in the southern Pacific Ocean that is a strong predictor of precipitation anomalies, and therefore drought or flooding, around the globe.

Image of the ENSO phases.
ENSO warm and cool phases from University of Alaska-Fairbanks Physics Department

In fact, this summer we are seeing a strong El Niño, also known as a positive ENSO, corresponding with a strong, positive PDO.

Researchers have known or suspected since the early 20th century that El Niño brings strong rains along the United States’ west coast. However, we now know, thanks to the results of the study on the Baltoro Glacier, that the formation and expansion of glacial lakes in the Karakoram Himalayas also occurs during the warm phase of the PDO, in particular when it is in phase with ENSO.

What this means is that the same events that are the likely cause of recent heavy rains and storms hitting Southern California are also likely causing increased glacial melt in the Himalayas.

According to The Weather Chanel, “Los Angeles, San Diego and over a dozen other California cities set all-time rainfall records for the month of July.” In fact, a National Weather Service meteorologist described these recent rains as “super historic.”

Researchers are beginning to pay more attention to sea surface temperature in the Pacific Ocean, and around the globe, as we are realizing that they influence everything from strong storms in California to glacial melt in the Himalayas.

The PDO was only relatively recently discovered, found in 1997 due to its influence on Pacific Northwest salmon production. Understanding what scientists call teleconnections between these various natural phenomenon can help us better prepare ourselves for the volatile environment in which we live. Knowing ahead of time that when Southern California will have heavy storms, mountain villages in the Himalayas should be wary of glacial lake flooding, can help save time, money, and lives.