Category: Science

Source: NIWA – National Institute of Water and Atmospheric Research

A team of NIWA scientific divers have successfully searched for a freshwater freak of nature in Otago’s alpine lakes.

They have unearthed plants that comprise moss and liverwort species, which are collectively known as deep-water bryophytes when found deep within lakes.

They were first discovered by NIWA divers in Otago’s lakes in the 1980s and 1990s and are a globally rare plant community, with New Zealand being one of the few places worldwide to support blankets of these species.

This year, Otago Regional Council (ORC) commissioned NIWA to undertake a submerged plant survey in Lakes Whakatipu, Wānaka, and Hāwea, hoping to build upon the knowledge gained over three decades ago and establish a regular monitoring protocol.

NIWA freshwater ecologist Mary de Winton was part of the dive team that first studied the bryophytes in the 1990s.

“I was apprehensive about whether we’d find them again because climate and lake catchments have changed a lot in 30 years, but we were delighted to see the plants still thriving down there. Bryophytes are usually found in moist environments like damp forest floors and shady rock faces, but we saw them in Lakes Whakatipu and Wānaka up to 50 m down.

“It’s a really unusual place for them to grow, but we think they were washed into the lakes eons ago and have found a niche in the quiet twilight depths. If it wasn’t for the extreme transparency of our lake water, we don’t think this ‘freak of nature’ would have survived,” said de Winton.

ORC’s Scientist – Lakes, Hugo Borges says the survey was a success, with more work planned later in the year.

“We haven’t done a full analysis yet, but we successfully revisited all sites and found deep-water bryophyte in some of them. We used a remotely operated vehicle to explore the lakebed, so have hours of footage to study – this will give us a better understanding of the extent of bryophytes coverage, which we can compare to the previous surveys,” says Mr Borges.

NIWA and ORC have scheduled a dive programme every three years to monitor Otago’s submerged plant communities.

The results of this initial study will provide a baseline to monitor the health of this unusual community, which will be crucial for tracking environmental change, while the depths they grow down to will provide an indicator of the long-term clarity of the lakes.

“Despite being simple organisms, deep-water bryophytes play a vital role in ecosystem functioning by providing habitats, improving water quality, and aiding biodiversity. They are highly sensitive gauges of water transparency, light transmission, sedimentation rates, temperature fluctuations, and changes in dissolved gases, all of which give us clues into the health of our freshwater environments,” says Mr Borges.

Light levels where deep-water bryophytes are found have been estimated at less than 1% of the sunlight falling on the lakes surface. A record of 128 m for deep-water bryophytes was described for an Oregon lake in the year 2000. 

Source: NIWA – National Institute of Water and Atmospheric Research

Ship anchors may cause extensive and long-lasting damage to the seafloor, according to new NIWA research.

NIWA anchored their research vessel in Wellington Harbour and observed in real-time how its anchor changed the surrounding environment.

Dr Sally Watson is a marine geophysicist at NIWA who led the study. She says they saw broomstick-like scarring on the seabed.

“Our preliminary findings showed marks on the seabed typical of an anchor being moved around due to wind and currents. The damage caused is often compared to that of trawling, but anchoring differs in that it tends to happen in shallow waters and repeatedly over the same locations, with potentially more intense and deeper seabed penetration,” said Dr Watson.

This work is part of a multi-year MBIE Smart Ideas project to redesign anchoring practices for a more sustainable shipping industry. Little research is available on how anchoring damages the environment, particularly in relation to larger vessels.

“Currently, most research is conducted on small recreational boats in shallow water, so this gave us a great insight into how bigger ships impact the seafloor at different depths. The findings will eventually be used to develop alternative solutions to current anchoring practices, including introducing new disturbance criteria and using designated drop points,” said Dr Watson.

During the study, Watson and her team anchored NIWA’s 73m long research vessel Tangaroa in Wellington Harbour, collecting over 1,000 water samples, taking before and after surveys of the seafloor, and capturing video footage from drones, a GoPro, and underwater cameras.

They battled several disturbances, including gales, shifts in wind direction, and changes in location due to other ships coming into port. Serendipitously, another vessel was anchored nearby and gave permission for NIWA to study their impact too, giving scientists a great comparison opportunity.

“These challenges were all blessings in disguise because we now have a rich set of data. The drone and GoPro footage was particularly fascinating, as they captured striking visuals of plumes of sediment being dredged from the seafloor as the anchors were raised,” said Dr Watson.

Globally, it is predicted that there will be a four-fold increase in shipping by 2050. Wellington Harbour is considered a moderate congestion port, handling approximately 13,000, 3.8 million tonnes of cargo, and 1.5 million passengers annually.

“This year, New Zealand saw its biggest ever summer cruise season, with 1,000 port visits and 300,000 passengers. Cruise ships often visit pristine locations and are a massive and a constant presence, so they likely put huge pressure on marine ecosystems,” said Dr Watson.

NIWA were also able to compare their findings to underwater maps taken of the same area in 2009. They discovered that some features were still visible on the seabed over 15 years later.

“Until this point, we knew that damage could last up to four years, but it turns out the legacy lasts a lot longer – our marine activities can leave their mark over decades. Anchoring may need to be rethought to mitigate potential impacts to the marine environment, while balancing this against the projected growth in shipping,” said Dr Watson.

CentrePort, which has been a key contributor to the study, indicated this work was important and aligned with its efforts to continuously improve the management of environmental risks and impacts to the harbour.

“We’re eager to support efforts that improve the sustainability of the shipping industry and continue to improve the management of environmental risks and impacts, such as those that may prove to be associated with ship anchors. While most of the ships that come to Wellington don’t anchor, studies like this offer a great opportunity to learn more and gather vital information that will inform what the shipping industry does to protect the precious marine floor,” Environmental Manager Thomas Marchant said.

The next stages in this project involve case studies from around Aotearoa New Zealand using ship tracking technology, as well as analysing biological data. 

Source: NIWA – National Institute of Water and Atmospheric Research

A weekly update describing soil moisture patterns across the country to show where dry to extremely dry conditions are occurring or imminent. Regions experiencing significant soil moisture deficits are deemed “hotspots”. Persistent hotspot regions have the potential to develop into drought.

Recent rainfall and current soil moisture conditions:

North Island:

• The upper and central North island generally saw rainfall totals of 25-50 mm in the past week, with localised amounts of 75 mm or more.
• However, generally meagre rainfall occurred along the east coast, where totals were less than 10 mm.
• Moderate to large soil moisture increases were observed across the western and central North Island in the past week, but additional decreases occurred along the east coast.
• The driest soils across the North Island, when compared to normal for this time of the year, are found in the Coromandel Peninsula, Gisborne, and Hawke’s Bay, while the wettest soils for this time of the year are found in western Northland along with western and southern Waikato.
• Most previous hotspots in the upper North Island, Manawatū-Whanganui and western Wellington have now dissipated, but hotspots are still located in parts of the Coromandel Peninsula and much of the east coast from East Cape to Wairarapa.
• As of 12 April, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Northland, northern Auckland, Coromandel Peninsula, coastal Gisborne and Hawke’s Bay, coastal Taranaki, southern Manawatū-Whanganui, and Wellington. Very dry to extremely dry conditions are located in much of Northland, northern Coromandel, southern Hawke’s Bay, and Wellington, while parts of eastern Northland are experiencing meteorological drought.

South Island:

• Very heavy rain affected the West Coast in the past week, with high elevations receiving 500 mm or more in many instances. The upper South Island also received substantial rainfall totals of 60-120 mm.
• Interior Canterbury, Otago, and Southland received 30-60 mm, but the east coast generally saw 10-25 mm.
• This resulted in moderate to large soil moisture increases across much of the South Island, although northern Canterbury saw little change.
• The driest soils across the South Island, when compared to normal for this time of the year, are found in northern Canterbury, while the wettest soils for this time of the year are found in Marlborough and western Southland.  
• Previous hotspots in the upper South Island have all dissipated due to the recent rainfall, but hotspots are still located in coastal northern and central Canterbury.  
• As of 12 April, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in northern Tasman, Nelson, northern Marlborough, parts of Canterbury, and northern Otago. Very dry to extremely dry conditions are located in northern Tasman, Nelson, western Marlborough, and parts of northern Canterbury.

Pictured above: Soil Moisture Anomaly Maps, relative to this time of year. The maps show soil moisture anomalies over the past two weeks.

As of 12 April, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Northland, northern Auckland, Coromandel Peninsula, coastal Gisborne and Hawke’s Bay, coastal Taranaki, southern Manawatū-Whanganui, Wellington, northern Tasman, Nelson, northern Marlborough, parts of Canterbury, and northern Otago. Very dry to extremely dry conditions are located in much of Northland, northern Coromandel, southern Hawke’s Bay, Wellington, northern Tasman, Nelson, western Marlborough, and parts of northern Canterbury. In addition, parts of eastern Northland are experiencing meteorological drought. Please note: some hotspots in the text above may not correspond with the NZDI map. This difference exists because the NZDI uses additional dryness indices, including one which integrates the rainfall deficit over the past 60 days. Changes are therefore slower to appear in the NZDI compared to soil moisture anomaly maps that are instantaneously updated.

The week ahead:

North Island:

• Daily rounds of showers will affect the northern and western North Island from Monday to Friday (15-19 April), while the east coast will remain generally dry during this time. 
• A more substantial area of rain may move across the island on Friday night and Saturday morning, followed by more isolated showers on Sunday (21 April).
• Weekly rainfall totals could reach 25-50 mm across the upper and western North Island. However, rainfall totals along the east coast may be 15 mm or less.
• Due to the expected rainfall in the next week, small soil moisture increases may occur in the western North Island, but small decreases could again occur along the east coast.
• Current hotspots located along the east coast could strengthen slightly in the next week.  

South Island:

• Showers will move through the West Coast and lower South Island on Tuesday (16 April), followed by mostly dry weather across the island on Wednesday and Thursday.
• However, a more substantial band of rain will move across the island on Friday (19 April). More showers will be possible on Sunday (21 April).  
• Weekly rainfall totals could reach 50-120 mm along the West Coast, with 25-50 mm possible in the lower South Island.
• However, lighter rainfall totals of less than 25 mm are likely in the upper and eastern South Island.
• Due to the expected rainfall in the next week, some soil moisture decreases may occur in the upper and eastern South Island, with other regions generally seeing little change.
• The current hotspots located in Canterbury may strengthen at least slightly in the next week.

Long-term outlook (through mid-May):

• The drier (25^th percentile) and middle (50^th percentile) rainfall scenarios both show near normal to below normal rainfall across much of both islands.
• In the wetter (75^th percentile) scenario, near normal to above normal rainfall is signalled across much of the country.
• Very dry soil conditions may affect parts of eastern NZ in the middle and drier scenarios, but this is not forecast to be widespread.  

Pictured above: 35-day forecast rainfall anomaly scenarios (Top), and 35-day forecast dryness and drought scenarios (Bottom). These maps are updated daily at https://niwa.co.nz/climate/seasonal-climate-outlook 

Background:

Hotspot Watch: a weekly advisory service for New Zealand media. It provides soil moisture and precipitation measurements around the country to help assess whether extremely dry conditions are imminent. 

Soil moisture deficit:  the amount of water needed to bring the soil moisture content back to field capacity, which is the maximum amount of water the soil can hold.

Soil moisture anomaly:  the difference between the historical normal soil moisture deficit (or surplus) for a given time of year and actual soil moisture deficits.

Definitions: “Extremely” and “severely” dry soils are based on a combination of the current soil moisture status and the difference from normal soil moisture (see soil moisture maps at https://www.niwa.co.nz/climate/nz-drought-monitor/droughtindicatormaps)

Hotspot: A hotspot is declared if soils are “severely drier than normal” which occurs when Soil Moisture Deficit (SMD) is less than -110 mm AND the Soil Moisture Anomaly is less than -20 mm.

Source: NIWA – National Institute of Water and Atmospheric Research

A weekly update describing soil moisture patterns across the country to show where dry to extremely dry conditions are occurring or imminent. Regions experiencing significant soil moisture deficits are deemed “hotspots”. Persistent hotspot regions have the potential to develop into drought.

Recent rainfall and current soil moisture conditions:

North Island:

• Rainfall totals of 10-25 mm were generally observed in the eastern North Island in the past week, although northern Hawke’s Bay saw an area of 30-40 mm.
• However, it was another week of generally meagre rainfall for the rest of the North Island, where totals were mostly 10 mm or less.
• Small to moderate soil moisture decreases were observed across nearly the entire North Island in the past week.  
• The driest soils across the North Island, when compared to normal for this time of the year, are found in eastern Northland, the northern Coromandel Peninsula, and parts of Taranaki and Wellington, while the wettest soils for this time of the year are found in western and southern Waikato.
• Hotspots are currently located across most of Northland, northern Auckland, northern Coromandel Peninsula, parts of coastal Bay of Plenty and Gisborne, southern Hawke’s Bay to Wairarapa, and coastal Manawatū-Whanganui to Kāpiti Coast.
• As of 2 April, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Northland, northern Auckland, northern Coromandel Peninsula, southern Hawke’s Bay, southern Manawatū-Whanganui, and Wellington. Very dry to extremely dry conditions are located in much of Northland and Wellington, while parts of eastern Northland are now experiencing meteorological drought.

South Island:

• Much of the West Coast and Fiordland received 20-50 mm in the past week, with up to 25 mm in Southland.
• However, the upper and eastern South Island again received meagre rainfall amounts of 5 mm or less.
• This resulted in small soil moisture decreases across the entire South Island.
• The driest soils across the South Island, when compared to normal for this time of the year, are found in northern Tasman, while the wettest soils for this time of the year are found in western Southland.  
• Hotspots are currently located across northern and eastern Tasman, Nelson, parts of Marlborough, and northern and central Canterbury, while southern Canterbury and eastern Otago are near hotspot status.
• As of 2 April, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in northern Tasman, Nelson, parts of Marlborough, several parts of Canterbury, and northern Otago. Very dry to extremely dry conditions are located in northern Tasman, Nelson, western Marlborough, parts of northern and far southern Canterbury, and northern Otago.

Pictured above: Soil Moisture Anomaly Maps, relative to this time of year. The maps show soil moisture anomalies over the past two weeks.

As of 2 April, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Northland, northern Auckland, northern Coromandel Peninsula, southern Hawke’s Bay, southern Manawatū-Whanganui, Wellington, northern Tasman, Nelson, parts of Marlborough, several parts of Canterbury, and northern Otago. Very dry to extremely dry conditions are located in much of Northland, Wellington, northern Tasman, Nelson, western Marlborough, parts of northern and far southern Canterbury, and northern Otago. In addition, parts of eastern Northland are experiencing meteorological drought. Please note: some hotspots in the text above may not correspond with the NZDI map. This difference exists because the NZDI uses additional dryness indices, including one which integrates the rainfall deficit over the past 60 days. Changes are therefore slower to appear in the NZDI compared to soil moisture anomaly maps that are instantaneously updated.

The week ahead:

North Island:

• A front will move up the North Island through Friday morning (5 April), bringing showers to most regions.
• From Friday afternoon, high pressure will deliver several consecutive days of generally dry weather through Wednesday of next week (10 April).
• However, an area of low pressure could bring moderate to heavy rain to the North Island around Thursday-Friday (11-12 April).
• Weekly rainfall totals could reach 25-50 mm across much of the North Island by late next week, with isolated higher amounts. However, rainfall totals along the east coast may be lower.
• Due to the expected rainfall in the next week, at least small soil moisture increases are likely across much of the North Island, although little change may occur along the east coast.
• Current hotspots in the upper and western North Island will have the best chance to ease somewhat in the next week, while those located along the east coast may not change significantly.

South Island:

• High pressure will result in mostly dry weather across the South Island through Monday (8 April).
• However, Tuesday through Thursday (9-11 April) look to be quite active, with heavy rain impacting the western South Island and some rain spilling over into the eastern South Island.
• Weekly rainfall totals could be quite substantial in the West Coast, with 200-400 mm possible.
• Amounts of 40-75 mm will be possible in the upper South Island, with 30-50 mm in the lower South Island.
• However, lower rainfall amounts of 25 mm or less are possible along the east coast.
• Due to the expected rainfall in the next week, meaningful soil moisture increases will be likely in the western and upper South Island, with smaller increases in the south, and little change along the east coast.
• The current hotspots in the upper South Island may ease moderately to substantially in the next week, while those located in Canterbury may not change substantially.

Long-term outlook (through early May):

• The drier (25^th percentile) and middle (50^th percentile) rainfall scenarios both show drier than normal conditions across much of both islands, leading to higher confidence for that outcome.
• In the middle (50^th percentile) scenario and wetter (75^th percentile) scenario, near normal to above normal rainfall is signalled in the eastern North Island and parts of the West Coast.
• Very dry soil conditions will affect the upper and eastern South Island in all three rainfall scenarios, with areas of meteorological drought signalled in the upper South Island in all three scenarios.

Pictured above: 35-day forecast rainfall anomaly scenarios (Top), and 35-day forecast dryness and drought scenarios (Bottom). These maps are updated daily at https://niwa.co.nz/climate/seasonal-climate-outlook 

Background:

Hotspot Watch: a weekly advisory service for New Zealand media. It provides soil moisture and precipitation measurements around the country to help assess whether extremely dry conditions are imminent. 

Soil moisture deficit:  the amount of water needed to bring the soil moisture content back to field capacity, which is the maximum amount of water the soil can hold.

Soil moisture anomaly:  the difference between the historical normal soil moisture deficit (or surplus) for a given time of year and actual soil moisture deficits.

Definitions: “Extremely” and “severely” dry soils are based on a combination of the current soil moisture status and the difference from normal soil moisture (see soil moisture maps at https://www.niwa.co.nz/climate/nz-drought-monitor/droughtindicatormaps)

Hotspot: A hotspot is declared if soils are “severely drier than normal” which occurs when Soil Moisture Deficit (SMD) is less than -110 mm AND the Soil Moisture Anomaly is less than -20 mm.

Source: NIWA – National Institute of Water and Atmospheric Research

A weekly update describing soil moisture patterns across the country to show where dry to extremely dry conditions are occurring or imminent. Regions experiencing significant soil moisture deficits are deemed “hotspots”. Persistent hotspot regions have the potential to develop into drought.

Recent rainfall and current soil moisture conditions:

North Island:

• Rainfall totals of 20-40 mm were generally observed in the western and central North Island in the past week.
• However, much of Northland, Auckland, the east coast, and lower North Island only received meagre rainfall totals of 5 mm or less.
• Overall the soil moisture situation across the North Island did not change significantly in the past week, although additional soil moisture decreases were observed in the eastern and lower North Island.
• The driest soils across the North Island, when compared to normal for this time of the year, are found in eastern Northland and the northern Coromandel Peninsula, while the wettest soils for this time of the year are found in western and southern Waikato.
• Hotspots are currently located across most of Northland, northern Auckland, northern Coromandel Peninsula, parts of coastal Gisborne, southern Hawke’s Bay to Wairarapa, and coastal Manawatū-Whanganui to Kāpiti Coast.
• As of 26 March, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Northland, northern Auckland, northern Coromandel Peninsula, southern Hawke’s Bay, southern Manawatū-Whanganui and Wellington. Very dry to extremely dry conditions are located in much of Northland and Wellington. In addition, parts of eastern Northland are on the precipice of meteorological drought.

South Island:

• Much of the West Coast and Fiordland received 50-100 mm in the past week, with isolated amounts above 125 mm.
• Rainfall in the upper West Coast, interior Canterbury, and Southland was as high as 25 mm.
• However, a majority of the upper South Island and coastal Canterbury only saw meagre totals of 5 mm or less.
• This resulted in small soil moisture decreases in the upper South Island along with small to moderate increases along the West Coast. Elsewhere, little change was observed.
• The driest soils across the South Island, when compared to normal for this time of the year, are found in northern Tasman, while the wettest soils for this time of the year are found in western Southland.  
• Hotspots are currently located across northern and eastern Tasman, Nelson, parts of Marlborough, northern and central Canterbury, and small parts of eastern Otago, although the remainder of Canterbury and eastern Otago are near hotspot status.
• As of 26 March, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in eastern Tasman, Nelson, Marlborough, several parts of Canterbury, and northern Otago. Very dry to extremely dry conditions are located in eastern Tasman, Nelson, western Marlborough, parts of northern and far southern Canterbury, and northern Otago.

Pictured above: Soil Moisture Anomaly Maps, relative to this time of year. The maps show soil moisture anomalies over the past two weeks.

As of 26 March, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Northland, northern Auckland, northern Coromandel Peninsula, southern Hawke’s Bay, southern Manawatū-Whanganui, Wellington, eastern Tasman, Nelson, Marlborough, several parts of Canterbury, and northern Otago. Very dry to extremely dry conditions are located in much of Northland, Wellington, eastern Tasman, Nelson, western Marlborough, parts of northern and far southern Canterbury, and northern Otago. In addition, parts of eastern Northland are on the precipice of meteorological drought. Please note: some hotspots in the text above may not correspond with the NZDI map. This difference exists because the NZDI uses additional dryness indices, including one which integrates the rainfall deficit over the past 60 days. Changes are therefore slower to appear in the NZDI compared to soil moisture anomaly maps that are instantaneously updated.

The week ahead:

North Island:

• Scattered showers will affect most of the island on Friday (29 March), with the heaviest showers along the east coast.
• The east coast will continue to see rain on Saturday (30 March) while other regions will be mostly dry.
• From Sunday, generally dry weather is expected through Wednesday (3 April).
• Late next week, an arriving front could bring light to moderate rain.
• Weekly rainfall totals are likely to be meagre once again, especially in the upper North Island where amounts are likely to remain below 10 mm. Along the east coast and lower North Island, weekly amounts are likely to be 20 mm or less.
• Due to the expected rainfall in the next week, additional soil moisture decreases are likely in the upper North Island, with generally little change expected elsewhere.
• Current hotspots in the upper North Island will have the best chance to strengthen in the next week, while those located elsewhere may not change significantly.

South Island:

• Other than isolated showers on Friday (29 March), high pressure will bring generally dry weather through Tuesday (2 April).
• A front could bring at least moderate rain to the West Coast during the middle of next week. 
• Weekly rainfall totals of 40-60 mm will occur across much of the West Coast, with 15-30 mm possible in the lower South Island.
• However, meagre rainfall amounts of 10 mm or less are possible in the upper and eastern South Island.
• Due to the expected rainfall in the next week, additional soil moisture decreases will be likely in the upper and eastern South Island, while other regions may see little change.
• The current hotspots in the South Island will likely strengthen and expand in the next week, with new hotspots potentially forming in southern Canterbury and Otago.  

Long-term outlook (through late April):

• The drier (25^th percentile) and middle (50^th percentile) rainfall scenarios both show drier or much drier than normal conditions across the upper North Island and much of the South Island, leading to higher confidence for that outcome.
• In the middle (50^th percentile) scenario and wetter (75^th percentile) scenario, above normal rainfall is signalled in the eastern North Island.
• Very dry soil conditions will affect the upper and eastern South Island in all three rainfall scenarios, with meteorological drought signalled in the upper South Island in the drier scenario.

Pictured above: 35-day forecast rainfall anomaly scenarios (Top), and 35-day forecast dryness and drought scenarios (Bottom). These maps are updated daily at https://niwa.co.nz/climate/seasonal-climate-outlook 

Background:

Hotspot Watch: a weekly advisory service for New Zealand media. It provides soil moisture and precipitation measurements around the country to help assess whether extremely dry conditions are imminent. 

Soil moisture deficit:  the amount of water needed to bring the soil moisture content back to field capacity, which is the maximum amount of water the soil can hold.

Soil moisture anomaly:  the difference between the historical normal soil moisture deficit (or surplus) for a given time of year and actual soil moisture deficits.

Definitions: “Extremely” and “severely” dry soils are based on a combination of the current soil moisture status and the difference from normal soil moisture (see soil moisture maps at https://www.niwa.co.nz/climate/nz-drought-monitor/droughtindicatormaps)

Hotspot: A hotspot is declared if soils are “severely drier than normal” which occurs when Soil Moisture Deficit (SMD) is less than -110 mm AND the Soil Moisture Anomaly is less than -20 mm.

Source: NIWA – National Institute of Water and Atmospheric Research

New Zealand’s glaciers appear “smashed and shattered” due to enduring ice loss, says NIWA.

Since the 1970s, NIWA has been flying over Aotearoa New Zealand’s mountain ranges to conduct their end of summer snowline survey, observing the state of our glaciers and elevation of the snowline.

Dr Andrew Lorrey is the programme lead and NIWA’s Principal Scientist – Climate and Environmental Applications. He said the research paints a picture of how Aotearoa’s stunning landscape is transforming.

“This year, we covered nearly the full set of index glaciers that have been monitored since the 1970s. We flew to the southern-most glaciers, ones that we’ve not seen since 2018. Back then, they were incredibly small and functionally dead, and one is now two thirds of the size it was on our last visit.

“Overall, the snowline has been rising and in the most recent years we’re seeing that rise accelerate, so we’re experiencing a continued trend of glacial ice loss,” said Dr Lorrey.

The past decade has seen eight of the 10 warmest years that New Zealand has experienced since records began. 2023 was the 2 nd warmest year on record – a trend that followed the rest of the world, with 86% of the planet having above average temperatures that year.

“Even if we got a few cooler seasons, they wouldn’t be enough to undo the damage that’s already been done. My colleague Dr Trevor Chinn, who started the survey nearly 50 years ago, put it perfectly – he said that the difference between today and five decades ago is like going to a ski field in the summer and then in the winter. That’s how stark it is, and it’s not just happening in New Zealand but all over the world,” said Dr Lorrey.

Glaciers form a significant part of New Zealand’s environment, economy, and culture. They are important sources of meltwater, which sustains stream habitats, as well as delivering nutrients into lakes, rivers, and oceans.

They also feed hydroelectric lakes, impacting the availability of renewable energy, and contribute millions of dollars to New Zealand’s economy through tourism (estimated at NZD 100 million in 2007).

“New Zealand is one of the few mid-latitude places where people live near glaciers, where people can see and visit them easily. But this is getting tougher. Tourism operators are having to penetrate further and further into the mountains to reach them.

“They hold tremendous value, but I worry that they won’t be around for our children to enjoy. Not to mention the impacts their disappearance will have on our environment and cultural heritage. A warming planet means fewer cold places and less ice. The message remains the same: we must tackle the issue of rising greenhouse gases if we are to save our glaciers from melting away,” said Dr Lorrey.

Source: NIWA – National Institute of Water and Atmospheric Research

NIWA and NIWAWeather social media accounts are places for people interested in climate, weather, freshwater and marine science. We welcome comments and look forward to joining the conversation. To ensure the quality of discussion, please don’t:  

• harass, insult or be abusive toward others
• make defamatory, libellous, false or misleading comments
• use obscene, insulting, racist, sexist or otherwise discriminatory or offensive language
• promote unsubstantiated, non-scientific theories
• post personal information about yourself or others such as private addresses or phone numbers
• promote commercial interests
• violate the intellectual property rights of others
• violate any laws or regulations
• post multiple versions of the same view to the wall or make excessive postings on a particular issue. 

NIWA will remove any comments or posts that it feels breach these terms of use. Offenders may be blocked from contributing to our pages. Please also refer to and comply with Facebook’s Rights and Responsibilities statement, as well as NIWA’s Privacy Policy.

Source: NIWA – National Institute of Water and Atmospheric Research

A weekly update describing soil moisture patterns across the country to show where dry to extremely dry conditions are occurring or imminent. Regions experiencing significant soil moisture deficits are deemed “hotspots”. Persistent hotspot regions have the potential to develop into drought.

Recent rainfall and current soil moisture conditions:

North Island:

• Parts of the central North Island including Waikato, Bay of Plenty, and Hawke’s Bay saw moderate rainfall amounts in the past week of 20-40 mm.
• However, upper and lower parts of the North Island generally received meagre rainfall amounts of 10 mm or less.
• Overall the soil moisture situation across the North Island did not change significantly in the past week, but some small additional decreases were observed.    
• The driest soils across the North Island, when compared to normal for this time of the year, are found in eastern Northland and the northern Coromandel Peninsula, while the wettest soils for this time of the year are found in western and southern Waikato.
• Hotspots are currently located across most of Northland, northern Auckland, southern Hawke’s Bay to Wairarapa, and Kāpiti Coast.
• As of 20 March, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Northland, Auckland, northern Coromandel Peninsula, eastern Bay of Plenty, southern Hawke’s Bay, southern Manawatū-Whanganui and Wellington. Very dry to extremely dry conditions are located in much of Northland and Wellington. In addition, parts of eastern Northland are on the precipice of meteorological drought.

South Island:

• Much of the South Island saw rainfall totals of 15-25 mm in the past week, with pockets of the lower South Island receiving 30-40 mm.
• Rainfall was again meagre in Tasman, Nelson, and much of Marlborough where weekly totals were less than 10 mm.
• This resulted in small soil moisture decreases across much of the South Island, although central and southern Canterbury and eastern Otago saw minor soil moisture increases.     
• The driest soils across the South Island, when compared to normal for this time of the year, are found in northern Tasman, while the wettest soils for this time of the year are found in western Southland.  
• Hotspots are currently located across eastern Tasman, Nelson, parts of Marlborough, large portions of Canterbury, and small parts of eastern Otago, although the remainder of Canterbury and Otago are near hotspot status.
• As of 20 March, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Wellington, eastern Tasman, Nelson, several parts of Canterbury, and eastern Otago. Very dry to extremely dry conditions are located in Nelson, parts of Marlborough, parts of northern and far southern Canterbury, and northern Otago.

Key Messages for the Top of the South Island:

• From October 2023 through February 2024, Blenheim recorded just 88 mm of rain – the lowest rainfall over that period since at least 1941.
• Many parts of the region experienced six or seven consecutive months with below normal rainfall, depending on the location.
• This severe rainfall deficit culminated in a precipitation drought for parts of Marlborough, Nelson, and Tasman.
• Read the government’s declaration of a medium-scale adverse event here.

Pictured above: Soil Moisture Anomaly Maps, relative to this time of year. The maps show soil moisture anomalies over the past two weeks.

As of 20 March, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Northland, Auckland, northern Coromandel Peninsula, eastern Bay of Plenty, southern Hawke’s Bay, southern Manawatū-Whanganui, Wellington, eastern Tasman, Nelson, several parts of Canterbury, and eastern Otago. Very dry to extremely dry conditions are located in much of Northland, Wellington, Nelson, parts of Marlborough, parts of northern and far southern Canterbury, and northern Otago. In addition, parts of eastern Northland are on the precipice of meteorological drought. Please note: some hotspots in the text above may not correspond with the NZDI map. This difference exists because the NZDI uses additional dryness indices, including one which integrates the rainfall deficit over the past 60 days. Changes are therefore slower to appear in the NZDI compared to soil moisture anomaly maps that are instantaneously updated.

The week ahead:

North Island:

• An area of light to moderate rain will move across the upper half of the North Island on Saturday (23 March), followed by scattered showers on Sunday afternoon (24 March).
• Monday through Wednesday (25-27 March) will feature isolated to scattered showers in western regions, while other areas generally remain dry.
• There will be a better chance for more numerous showers or even areas of steadier rain towards the end of next week.
• Weekly rainfall totals of 30-50 mm will be possible in the western and central North Island, but eastern Northland and parts of the east coast may again see light rainfall totals below 15 mm.
• Due to the expected rainfall in the next week, moderate soil moisture increases may occur in the western North Island, but additional decreases may occur in the Far North and parts of the east coast.
• Current hotspots in the Far North and lower east coast will have the best chance to strengthen at least slightly in the next week.

South Island:

• A few showers will affect the lower South Island on Saturday afternoon (23 March).
• Monday through Thursday (25-28 March) will likely be quite unsettled, with several rounds of moderate to heavy rain affecting the West Coast and lower South Island. However, the upper South Island and coastal Canterbury may miss out on the bulk of this rainfall.
• Weekly rainfall totals of 100-200 mm will affect the central and lower West Coast, with 30-70 mm possible in parts of Otago and Southland.
• However, coastal Canterbury and the upper South Island may only receive 15-20 mm or less.
• Due to the expected rainfall in the next week, additional soil moisture decreases could occur in the upper South Island, while notable increases will be possible in the lower South Island and parts of the West Coast.
• The current hotspots in the upper South Island could strengthen at least slightly in the next week, with those in southern Canterbury and Otago potentially easing to an extent.  

Long-term outlook (through late April):

• The drier (25^th percentile) and middle (50^th percentile) rainfall scenarios both show drier or much drier than normal conditions across nearly all of New Zealand , leading to higher confidence for that outcome.
• Even in the wetter (75^th percentile) scenario, below normal rainfall remains forecast in many regions across both islands.
• Very dry soil conditions could affect the eastern South Island in all three rainfall scenarios, along with parts of the upper and eastern North Island in the drier scenario.

Pictured above: 35-day forecast rainfall anomaly scenarios (Top), and 35-day forecast dryness and drought scenarios (Bottom). These maps are updated daily at https://niwa.co.nz/climate/seasonal-climate-outlook 

Background:

Hotspot Watch: a weekly advisory service for New Zealand media. It provides soil moisture and precipitation measurements around the country to help assess whether extremely dry conditions are imminent. 

Soil moisture deficit:  the amount of water needed to bring the soil moisture content back to field capacity, which is the maximum amount of water the soil can hold.

Soil moisture anomaly:  the difference between the historical normal soil moisture deficit (or surplus) for a given time of year and actual soil moisture deficits.

Definitions: “Extremely” and “severely” dry soils are based on a combination of the current soil moisture status and the difference from normal soil moisture (see soil moisture maps at https://www.niwa.co.nz/climate/nz-drought-monitor/droughtindicatormaps)

Hotspot: A hotspot is declared if soils are “severely drier than normal” which occurs when Soil Moisture Deficit (SMD) is less than -110 mm AND the Soil Moisture Anomaly is less than -20 mm.

Source: NIWA – National Institute of Water and Atmospheric Research

A weekly update describing soil moisture patterns across the country to show where dry to extremely dry conditions are occurring or imminent. Regions experiencing significant soil moisture deficits are deemed “hotspots”. Persistent hotspot regions have the potential to develop into drought.

Recent rainfall and current soil moisture conditions:

North Island:

• Meagre rainfall was widespread across the entire North Island in the past week, with most locations receiving 5 mm or less. Isolated pockets up to 15 mm were observed in the Coromandel Peninsula and parts of the Central Plateau.
• This resulted in moderate soil moisture decreases across the entire North Island.   
• The driest soils across the North Island, when compared to normal for this time of the year, are found in eastern Northland, while the wettest soils for this time of the year are found in western and southern Waikato.
• Hotspots are currently located across the Far North and eastern Northland, far northern Auckland, coastal Gisborne, southern Hawke’s Bay to Wairarapa, and parts of western Wellington.
• As of 13 March, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Northland, Auckland, part of the Coromandel Peninsula, eastern Bay of Plenty, and much of the lower North Island. Very dry to extremely dry conditions are located in much of Northland and Wellington.

South Island:

• Much like the North Island, a majority of the South Island saw only meagre rainfall in the past week, with 5 mm or less observed in most of the upper and eastern South Island.
• Pockets of the upper West Coast, central Canterbury, and Southland received up to 20 mm.
• Weekly rainfall totals in the lower West Coast and Fiordland were much higher, however, with generally 50-100 mm observed.  
• This resulted in small to moderate soil moisture decreases across most of the upper and eastern South Island, with little change observed elsewhere.    
• The driest soils across the South Island, when compared to normal for this time of the year, are found across parts of Tasman, Nelson, Marlborough Sounds, and Canterbury, while the wettest soils for this time of the year are found in western Southland.  
• Hotspots are currently located across much of the upper and eastern South Island, including eastern Tasman, Nelson, parts of Marlborough, nearly all of Canterbury, and eastern Otago.
• As of 13 March, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in eastern Tasman, Nelson, Marlborough, northern and southern Canterbury, and eastern Otago. Very dry to extremely dry conditions are located in Nelson, Marlborough, parts of northern and far southern Canterbury, and northern Otago.

Pictured above: Soil Moisture Anomaly Maps, relative to this time of year. The maps show soil moisture anomalies over the past two weeks.

As of 13 March, the New Zealand Drought Index (NZDI) map below shows that abnormally dry conditions are currently found in Northland, Auckland, part of the Coromandel Peninsula, eastern Bay of Plenty, much of the lower North Island, eastern Tasman, Nelson, Marlborough, northern and southern Canterbury, and eastern Otago. Very dry to extremely dry conditions are located in much of Northland, Wellington, Nelson, Marlborough, parts of northern and far southern Canterbury, and northern Otago. Please note: some hotspots in the text above may not correspond with the NZDI map. This difference exists because the NZDI uses additional dryness indices, including one which integrates the rainfall deficit over the past 60 days. Changes are therefore slower to appear in the NZDI compared to soil moisture anomaly maps that are instantaneously updated.

New Zealand Drought Index (NZDI) – 13 March 2024 [NIWA]