Arctic Sea Ice Extent Rapidly Decreasing Because of Climate Change; Weather & Climate Implications

Today, NOAA presented the State of the Arctic report at the American Geophysical Union annual conference in New Orleans. The news from the report was devastating for potential weather and climate impacts. Lots of important info to talk about from this! Let’s summarize:

  1. Annual Arctic sea ice extent is the lowest in 1600 years. This is based on proxy data (tree rings, lake sediments, ice cores from the Greenland Ice Sheet). There has been an abrupt decrease in extent during the 20th century (continuing to present). 24991395_10215050817330895_108575701643656859_n
  2. Arctic sea ice extent reached a record minimum in the warm season in 2012. However, 2015-17 witnessed consecutive record low maximum extents in the cold season. 2016 also had the lowest extent on record in November or December. 2017 is also witnessing top two or three low daily extents in November into December, with record low sea ice in the northern Bering Sea and the Chukchi Sea (north of the Bering Strait between Alaska and Russia). Also very notable, sea ice VOLUME (which includes thickness of ice) has continued to suffer with 2015-17 in the top 4 for the lowest volume on record going back to 1979 (and based on decreasing of sea ice extent and thickness, likely much much longer than that). Multi-year ice…ice more than a year old…is now nearly extinct in the Arctic Ocean.

    siv_annual_max_loss_and_ice_remaining
    Arctic Sea Ice Volume since 1979. Note consistent and accelerating collapse of sea ice volume. Arctic ice volume may fall below the 2012 record at some point in the month of September in the next several years.
  3. The Arctic had its warmest year on record in 2016 and its second warmest year on record in 2017 in reliable records. The climate of the Arctic is warming to the point that permafrost is increasingly melting releasing methane and carbon dioxide, methane emissions from what are called methane hydrates (methane gas locked in water ice) are increasing from the very shallow continental shelves surrounding the Arctic Ocean and mid-latitude weather patterns are becoming altered because of reduced sea ice (more on this shortly). The Arctic tundra is also greening at an increasing rate because of rapid warming.
  4. NOAA specifically states that “the Arctic shows no signs of returning to a reliably frozen region of recent decades” because of continued climate change related warming.

Discussion – Leaving the Ice Age Era:

One thing that we must remember about the sea ice of the Arctic Ocean (and the Southern Ocean around Antarctica) is that sea ice is a product of Ice Age eras. Our planet has had a tendency historically to flip between two global climate equilibrium states with dramatically different regional weather and seasonal patterns. The Ice Ages and the Hot House “Jurrasic Park” climates have been the two long-term dominating climate regimes in Earth’s history. One characterized by huge ice sheets and low sea levels, the other characterized by no ice sheets, no sea ice and high sea levels. Human civilization has flourished in the latest interglacial period in the Ice Age era because the climate has remained largely stable for roughly 10,000 years (-1 to +0.5 degrees C relative to mid-20th century climate) and mild enough to for extensive agriculture and settlements.

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Estimated temperature of Planet Earth from 550 million years ago to the end of the 20th century.

But now, because of Anthropogenic Global Warming (AGW) from climate change, we are leaving that stability in the geologic blink of an eye.

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Projected rise in global temperature of 4 degrees C/8 degrees F (relative to mid-20th century) during the 21st century relative to the past 10,000 years.

Probably the most important regulars of climate during Interglacials are the “refrigerators” of the north and south…the Arctic Ocean sea ice and Antarctic Ice Sheet (also Greenland Ice Sheet). However, as temperatures warm because of human carbon dioxide emissions trapping heat in the global climate system, that heat warms the atmosphere and ocean, attacking the sea ice by providing excess latent heat of melting. For the Arctic, this reduces the sea ice extent and volume decade after decade. Eventually, it will get to a point, where sea ice will become so thin and tenuous, it will undergo collapse to what has been called a “blue ocean” event with 1,000,000 sq km or less ice at a minimum in September (2012 extent minimum record was 3.41 million sq km). The 2016 and 2017 extent minimums were in the top 10 with 4.14 and 4.64 million sq km, 2nd and 8th respectively. 8 of the top 10 warm season minimum extents (in km) have occurred since 2010 in the now 39 year record. The Arctic Ocean and lower atmosphere are warming and becoming more like the high latitude North Atlantic. Eventually sea ice is expected to disappear completely in the warm season in the Arctic. Some climate scientists have suggested over the past several years that the “blue ocean” event resulting from a collapse of sea ice extent could occur between 2015-2020 or so as multi-year ice has nearly gone extinct, leaving thin ice vulnerable to quick melting and battering waves from cyclones. Computer models have been terrible at dealing with the end of sea ice in the Arctic, suggesting it would stick around into the second half of this century.

Discussion – Weather and Climate Implications:

So why does loss of sea ice matter? Sea ice regulates the climate of the world in multiple ways. It acts as large white surface which reflects most of the shortwave solar radiation from the sun (high albedo). As a result, it keeps the Arctic and Northern Hemisphere (and world) cooler than otherwise. It’s wide physical presence means heat entering the Arctic Ocean goes into melting the ice in the warm season (latent heat of melting; heat goes into phase change of water from solid to liquid) instead of heating the ocean and atmosphere dramatically (sensible heat to change temperature). Losing sea ice ends its presence as a climate regulator, allowing for more abrupt warming of the atmosphere-ocean system and increasing moisture content in the atmosphere (water vapor is an additional greenhouse gas; and increased clouds may reflect some radiation, but also can limit cooling in darkness). In addition, the Arctic Ocean will warm as it is a dark surface (low albedo). Increasing ocean warming in the marginal seas of the Arctic Ocean is already leading to increased methane emissions from the shallow continental shelves (as subsea permafrost thaw the clathrates) and more rapid warming will lead to an increase in emissions of methane and carbon dioxide from land permafrost (see discussion by Arctic climate scientist Dr. Peter Wadhams of Cambridge University on YouTube). Methane is over 100 times more powerful greenhouse gas than carbon dioxide on a timescale of several years (it dissipates far faster in the atmosphere, but sudden releases can increase warming quickly). And all of these feedbacks will much more quickly destroy the sea ice extent through further warming for a longer period in the warm season until ice disappears completely.

Increased warming of the Arctic also has impacts on mid-latitude weather. There has been research suggesting that the jet stream can be strongly influenced by Arctic warming and sea ice extent (see discussion by Dr. Jennifer Francis on YouTube). This can include a weakening of the upper-level jet stream which depends on the temperature difference between the upper-level mid-latitudes and polar atmosphere (known in meteorology as “baroclinic instability”). This weakening can lead to the jet stream developing high-amplitude waves more frequently, allowing for powerful upper-level ridges of high pressure to develop and cause blocking of the progressive westerly flow. This blocking can cause more frequent stagnant weather for locations, developing droughts in some areas through prolonged dryness, long periods of heavy precipitation in other regions as well as places of very abnormally warm temps (greater extreme summer heat) vs. colder temperatures (but the warmth always significantly outpaces the cold). Increased warming of the atmosphere in general also increases rainfall rates. In addition, paradoxically, while parts of the mid-latitudes may go through below normal temps and cold weather, the powerful ridging can produce extremely abnormally warm temperatures over the Arctic regions, intensifying the warming of the far north.

An identical pattern to this has largely set up over the Northern Hemisphere November into December.

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Powerful high-amplitude ridges over the Eastern Pacific and North Atlantic. Pattern relatively stagnant at this time.
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Reanalysis of the average temperature of Earth and specified regions over the last 30 days (1981-2010 baseline…add 0.7 C to compare to late 19th century). Note extensive, persistent anomalous warmth of the Arctic.

These effects may overall lead to more abrupt warming of the world as a whole as well as (more importantly) changes in rainfall and snowfall patterns, relevant for crops and food security from increasing summer extremes (heat stress and heavy rainfall) and water resources (snow pack, groundwater, etc). Also relevant for forest health (destruction by increasing wildfires as well as bug infestations killing hundreds of millions of trees in the Western US). And a running theme in stories on climate change recently? “Faster than expected” or “Faster than previously thought”. The importance of Arctic sea ice cannot be overstated and, unfortunately, this major tipping point…which I would consider a “keystone” tipping point because of what effects it can have down the line on other parts of the climate system…seems to be on the brink. It has been 2.6 million years since significant sea ice did not regularly exist in the warm season in the Arctic Ocean.

The statistics of weather has already changed significantly because of global warming with far more extreme heat events, drought periods and heavy precipitation events than in the mid-20th century (see presentation by Dr. Aaron Thierry on shift to more extreme weather conditions; starts 12:30 min, recommend watching through 20:30 min; also see discussion of climate change on increasing extreme events by Dr. Stefan Rahmstorf). Going past tipping points far earlier than expected by climate models will increase the likelihood for far more extreme weather events as weather patterns and circulations change (in some cases difficult to predict ways). Clearly, the world still needs adequate mitigation and adaptation measures to deal with these rapid and possibly abrupt changes.

For more info into how climate change influenced global extreme weather events in 2016, see the latest report (issued today) by the American Meteorological Society with attribution studies on last year’s significant events.

–Meteorologist Nick Humphrey

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La Nina Pattern Begins in the Pacific Ocean

A weak La Nina atmosphere-ocean pattern has fully developed in the Pacific Ocean. This phenomenon is part of the cool phase of the El Nino Southern Oscillation (ENSO). It is characterized by abnormally low surface pressure in the Western side of the Pacific Basin and abnormally high pressure on the Eastern side. This causes an enhancement of the easterly trade winds, causing significant upwelling of cold water along the equatorial coast of South America, with a build up of very warm water in the Western Pacific.

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Schematic of La Nina oceanic ocean-atmosphere pattern in the Pacific and expected jet stream behavior and temperature/precipitation impacts in the US/Canada during a La Nina winter.

ENSO patterns, as shown above can cause noticeable changes in the seasonal weather patterns over North America, particularly during the winter months. The jet stream can become more amplified, leading to a Pacific jet producing cooler and wetter than normal conditions over the Pacific Northwest, extending into the northern tier states. Meanwhile, the “Sun Belt” of the US can see abnormally warm, dry conditions.

The caveat of all this is is the strength of the La Nina versus the degree of influence other atmospheric patterns have on the seasonal climate variability. Other patterns include the North Atlantic Oscillation (NAO-surface pressure variability between the semi-permanent Icelandic Low and Azores High), Arctic Oscillation (AO-pressure anomalies between Arctic and mid-latitudes, closely related to NAO), and the Madden-Julian Oscillation (which can speed the development and enhance the effects of a El Nino or La Nina phase), among others on various timescales.

So what does it mean for our winter in the US? Well, as of now, the NWS Climate Prediction Center is generating winter temperature/precipitation forecasts accounting for the development of La Nina, with a strong latitudinal effect on temperature and precipitation. Below/above in the north and above/below in the south, respectively.

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In the meantime, long-range forecasts show the North Atlantic Oscillation becoming “negative” later in November (characterized by a south to north pressure gradient between the Azores high over Portugal and the Icelandic to the north). This pattern is favorable for an amplified upper-level jet stream wave pattern over North America and the North Atlantic and intrusions of cold air deep into the eastern half of the US. So in the shorter term colder than normal conditions may be possible for these areas this month (as has already occurred this week).

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When it comes to these “teleconnections”…the various cycles of variability within the annual climate regime of Earth…they can most definitely give us a head’s up on to what to expect in general. A canvas of how the weather may be behave over the course of days to weeks and months. But we must keep track of how these different cycles interact with each other and how they vary individually in terms of strength and mode. One curiosity is the strength and persistence of the La Nina. If it was fairly weak, it is more likely to be dominated by other teleconnections at times during the course of the winter, versus if it intensifies and produces more persistent effects on the upper-level air patterns.

Overall, the expected winter pattern is good news for drought-stricken areas in the northern tier such as Montana and the Dakotas. We will have to watch areas along the southern tier for potential further drought development. And as mentioned, November and at least early December could feature a more amplified jet stream so that even areas in the Southeast which may end up with an above average winter overall may see serious impacts from cold because of Arctic intrusions (something for citrus growers to watch out for in Florida, for example).

–Meteorologist Nick Humphrey

Key Findings of the US Government’s Climate Science Special Report

Today, the US Global Climate Change Research Program released the Climate Science Special Report, Vol. 1 of the Fourth National Climate Assessment mandated by Congress to provide the latest scientific basis and impacts from climate change on the United States. Climate science continues to evolve, but in the direction of more significant realization of how humans have influenced the climate thus far, as well as how much more influence will come in the not to distant future.

Below are some of the headline findings provided in the rather powerful report (be prepared for a lot of INTENSE info):

    1. Earth’s average temperature has increased by 1 degree C (1.8 F) during the 1901-2016 period. This is faster than any rate known in the last 1,700 years.                 2017TempUpdate_Top10_Global_F_en_title_lg
    2. The average temperature of the contiguous United States has also increased by 1 degree C (1.8 F) during the 1901-2016 period. Satellite and surface observations are consistent in the detection of this rapid rise in temperature. With no change in the rate of greenhouse gas emissions, the CONUS is expected to experience a more abrupt average rise in temperature of 3.2-6.6 degrees C (5.8-11.9 F) between now and 2100.                                                                                 
      figure6_1
      Change in average surface temperature (annual and seasonal) for the period 1986-2016 since the period 1901-1960 (contiguous US; 1925-1960 for Alaska and Hawaii). Data from NOAA.

      figure6_8
      Projected changes in the coldest and warmest daily temperatures (°F) of the year in the contiguous United States. Changes are the difference between the average for mid-century (2036–2065) and the average for near-present (1976–2005) under the higher emissions scenario (RCP8.5). Maps in the top row depict the weighted multimodel mean whereas maps on the bottom row depict the mean of the three warmest models (that is, the models with the largest temperature increase). Maps are derived from 32 climate model projections that were statistically downscaled using the Localized Constructed Analogs technique. Increases are statistically significant in all areas (that is­­, more than 50% of the models show a statistically significant change, and more than 67% agree on the sign of the change). Data by NOAA.
    3. Temperature extremes in the United States are trending significantly toward record high temperatures over record low temperatures. This trend is expected to continue with the number of below freezing days also continuing to decline and days above 32 degrees C (90 F) continuing to rise.
      figure6_5
      Data by NOAA.

      figure6_9
      Projected changes in the number of days per year with a maximum temperature above 90°F and a minimum temperature below 32°F in the contiguous United States. Changes are the difference between the average for mid-century (2036–2065) and the average for near-present (1976–2005) under the higher scenario (RCP8.5). Maps in the top row depict the weighted multimodel mean whereas maps on the bottom row depict the mean of the three warmest models (that is, the models with the largest temperature increase). Maps are derived from 32 climate model projections that were statistically downscaled using the Localized Constructed Analogs technique. Changes are statistically significant in all areas (that is, more than 50% of the models show a statistically significant change, and more than 67% agree on the sign of the change).
    4. The global influence of natural variability is limited to small fraction of observed climate trends. Solar output and the Earth’s internal natural variability have contributed only marginally to the observed changes in the climate system over the past century. There is no convincing evidence for natural cycles in the observational record that could explain the changes in the climate system.                                                                                                                                                         
    5. Heavy precipitation events have increased across the US since 1901. The highest increase over the Northeast and the second highest increase over the Midwest.                                                                                                                                2017ClimateExtremes_Downpours_3_en_title_lg
    6. Northern Hemisphere spring snow cover, North American maximum snow depth and Western US snow-liquid equivalent have all declined since the early 20th century. At current rates of decline and assuming no change in water resource management, chronic, long-duration hydrological drought conditions are possible for portions of the United States by 2100.                                                                                                                                                                                               
    7. Global mean sea-level has risen 7-8 inches (~0.2 m) since 1900 with 3 of those inches since 1993. Relative to the year 2000 is very likely global mean sea-levels will rise up to 0.6 ft (0.18 m) by 2030, 1.2 ft (0.38 m) by 2050 and 4.3 ft (1.3 m)+ by 2100. A more rapid degradation of the West Antarctic Ice Sheet may mean physically possible sea level rise theoretically exceeding 8 ft (2.4 m) by 2100 (confidence is low on this).                                                                                                                2016StateOfClimate_SLR_en_title_lg
    8. The global ocean has absorbed more than 93% of the heat caused by global warming since the mid-20th century. The oceans have warmed by about 0.7 degrees C (1.3 F) during the 1900-2016 period. Assuming no emissions changes, warming of the oceans by an average of 2.7 degrees C (4.9 F) is expected by 2100.                                                                                                                                       2016StateOfClimate_HeatStorage_en_title_lg
    9. The global ocean continues to undergo rapid acidification because of dissolved carbon dioxide from atmospheric emissions. The rate of acidification is unparalleled in the past 66 million years (since the Cretaceous-Paleogene Impact Event). At the current rate, the pH of the global ocean may decline from its current average of 8.1 to as low as 7.8 by the end of the century. Seawater with pH <8 can be corrosive to shellfish, plankton and coral which depend on carbonate structures for their shells, backbones and skeletons. The greatest change in acidity will be in Arctic Ocean.

      figure13_5-1200
      Predicted change in sea surface pH in 2090–2099 relative to 1990–1999 under the higher scenario (RCP8.5), based on the Community Earth System Models–Large Ensemble Experiments CMIP5 (Figure source: adapted from Bopp et al. 2013 ).
    10. The Arctic is warming at a rate approximately twice as fast as the global average with a rapid decline in sea ice volume and extent since satellite observations began in 1979. At the current rate of warming, the Arctic Ocean will be effectively ice-free in the month of September by the 2040s.                       

      siv_annual_max_loss_and_ice_remaining
      Arctic Sea Ice Volume since 1979. Note gradual and accelerating collapse of sea ice volume. Arctic may fall below 1,000 cubic kilometers at some point in the month of September in as early as several years to a decade or so. This will happen when the yearly sea ice maximum and loss of what remains equal.
    11. Global warming has contributed “significantly” to ocean-atmosphere variability in the North Atlantic Ocean; as a result these changes have contributed to the observed upward trend in North Atlantic hurricane activity since the 1970s. North Atlantic hurricanes are expected to increase in intensity (maximum sustained wind potential) with increasing precipitation rates during the 21st century.                                    2017Hurricanes_Info_en_title_lg

      figure9_2-1200
      Tracks of simulated Saffir–Simpson Category 4–5 tropical cyclones for (a) present-day or (b) late-21st-century conditions, based on dynamical downscaling of climate conditions from the CMIP5 multimodel ensemble (lower scenario; RCP4.5). The tropical cyclones were initially simulated using a 50-km grid global atmospheric model, but each individual tropical cyclone was re-simulated at higher resolution using the GFDL hurricane model to provide more realistic storm intensities and structure. Storm categories or intensities are shown over the lifetime of each simulated storm, according to the Saffir–Simpson scale. The categories are depicted by the track colors, varying from tropical storm (blue) to Category 5 (black; see legend). (Figure source: Knutson et al. 2015; © American Meteorological Society).
    12. Large forest fires in the Contiguous US and Alaska have increased since the early-1980s. This increase is expected to continue with “profound” impacts on ecosystems.                                                                                                                           2016Wildfires_temp_WEST_en_title_lg

Some other findings of note:

-For the period 1901-2016, the Dust Bowl Era (mid-1930s) remains the most extreme era for heat. This is thought to be largely the result of significant land-surface feedbacks caused by precipitation deficits and poor land management leading to reduced vegetation and strong surface heating (which in turn promoted further drying and land degradation). However, we are on a path to eclipse this period in US climate history in the coming decades, particularly as colder conditions (more found in 1930s winters for example) continue to decline in a warming climate and extreme heat continues to increase.

-The Climate report explains (as has been explained in previous scientific literature) the period of so-called “global cooling” which occurred from the mid-1940s to mid-1960s: aerosol particles generated by WWII and post-war industrial production (esp. coal power plants) which reflected some solar radiation into space temporarily slowing long-term global warming, even as carbon dioxide concentration in the atmosphere continued to increase.

-The report notes that annual precipitation has decreased over the West, Southwest and Southeast, while increases have occurred over the Plains, Midwest and Northeast. They specifically mention an increase in mesoscale convective systems (organized clusters of thunderstorms which dump significant rainfall) over the Plains and Midwest since 1979. Mesoscale convective systems are expected to increase in frequency and intensity during the 21st century.

-While tornado climatology related to climate change has been difficult to understand because of the reliability of storm reports before the 1990s, scientists involved in the report have concluded one interesting aspect…there is moderate confidence in a decrease in tornado days (day when tornadoes of any number are confirmed), as tornadoes are increasing on those days. Greater volatility in tornado occurrence year-to-year as well as a trend toward an earlier first occurrence during the year have been observed. Studies looking at the ingredients for severe storms with all modes of potential activity (tornadoes, hail, wind) suggest an increased frequency and intensity of severe storms over areas prone to them in the US in a warmer world, but confidence on details is low.

-This report concluded that observed drought and precipitation increases (1901-2016) cannot be confidently attributed human-induced global warming. The Dust Bowl Era remains the benchmark period for extreme drought conditions. However recent negative trends in soil moisture are believed to be attributable to warming temperatures. Although soil moisture projections in climate models are still considered in their “elementary” stages in the science, based on what is known, there appears to be a signal for further decreases in soil moisture over portions of the US (particularly West and Plains) by the end of this century, increasing the risk of chronic hydrological drought.

-I find the key finding #11 I listed particularly important. There has been much debate between scientists (particularly more observational minded meteorologists vs. climatologists) about whether there has been truly observable increase in N. Atlantic hurricane activity seasonally beyond the natural variability, given the limited period of reliable satellite record and intensity measurements. This statement is given MODERATE confidence given that global warming has caused increases in sea-surface temperatures, oceanic heat content and natural cycles on multi-annual and multidecadal time scales involve changes in not only these thermodynamic variables but also dynamic ones in response (vertical wind shear, position/intensity of monsoon troughs, development of tropical waves into organized TCs).

Additional Thoughts:

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Climate change will likely be one of the most difficult challenges the world will face this century (at least). Why? Why should we care?

When it comes to effects on people (which is what people care about), at the end of the day, what matters for the livelihood of people rich or poor? Food, water, living space. If these become challenged, you get human suffering (from economic to health threats) and geopolitical problems. The potential for significant drying and increasing chronic hydrologic droughts from loss of snowpack will lead to increasing populations in demand for resources seriously straining water resources. Crops around the world will face increasing difficulties from heat stress, prolonged droughts mixed with periods of more intense heavy rainfall events. Acidification and warming may threaten marine food resources already strained by overfishing around the world. Living space will become slowly threatened by sea level rise in low-lying areas and island nations…and more readily in the coming decades…by repeated far more extreme heat waves than previously in already hot, humid environments where cooling is not readily available, and possibly by diseases as ecosystems shift to different places, along with pests (which will also impact crops potentially).

Climate change isn’t just about warming, it’s about cascading impacts on the whole of the climate system. Without a drastic global shift to a low-carbon energy sources and the advancement of technology to remove carbon dioxide from the atmosphere, we are in store for a very challenging period in human history. This isn’t worse-case/best case or any of this. This is simply the path that we are on, no over-dramatic statements nor downplaying needed or tolerated. Hopefully we via our governments make the right choices.

–Meteorologist Nick Humphrey

Five Year Anniversary of Landfall of Superstorm Sandy

Five years ago today (October 29, 2012), the post-tropical remnants of what was Hurricane Sandy made landfall on the New Jersey coastline as a hurricane-force windstorm, causing destructive straight-line winds and historic, damaging surge from the North Atlantic extending from the Jersey coast north into the New York City Metro Area, with historic flooding of lower Manhattan.

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Image of extremely large Hurricane Sandy by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite on October 28, 2012. Sandy would become the largest tropical cyclone on record in the North Atlantic Basin.
Sandy produced widespread wind gusts of 75-90 mph across portions of New York and New Jersey with heavy rainfall totals of 7-10 inches across parts of New Jersey, Delaware, and Maryland. Storm surge was Sandy’s main cause of significant damage, with wind damage and flooding rainfall additional impacts. The post-tropical “superstorm” caused a 10-13 ft storm surge which damaged and destroyed homes and businesses along the Jersey Shore and Hudson Waterfront, with a record 13.88 ft water rise reported at Battery Park in Lower Manhattan.

Damage_from_Hurricane_Sandy_to_house_in_Brooklyn,_NY
Damage by Super Storm Sandy in Brooklyn, NY (“Proud Novice” on Wikipedia).
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Super Storm Sandy damage in Mantoloking, NJ taken on October 30, 2012. (US Air Force).
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The flooded Brooklyn-Battery subway tunnel in NYC on October 30, 2012 (“vcohen” on Wikipedia).
Sandy’s expansive storm surge was more intense by multiple factors. As it came poleward, it grew significantly in size, a typical phenomenon for tropical cyclones moving into the mid-latitudes. However, Sandy’s weakening and mid-latitude interactions caused it become the largest North Atlantic tropical cyclone on record, producing a huge fetch (extensive wind over long stretch of open water). This fetch allowed for the building of significant ocean waves and piling up of water toward the shallow continental shelf of the Atlantic coast of the US. And although Sandy weakened somewhat and became “non-tropical”, this did not matter as the very large wind field remained and forward momentum of the very heavy ocean could not settle down in time before pounding the coastline with destructive surge.

In addition, Sandy made landfall at high tide, enhancing the storm’s ability to flood dry land areas and cause direct damage with battering waves. I will also note that this “flood reach” was even greater because of climate change-induced sea level rise. Global sea levels have risen 9 inches since 1880 and while the Intergovernmental Panel on Climate Change (UN) continues to indicate a likely sea level rise of up to 3.2 ft by 2100, many other reputable scientists have suggested the possibility of multi-foot sea level rise occurring this century as the result of exponential glacial melt feedbacks in Greenland and Antarctica. Perhaps as high as 6.5-16.5 feet by 2100 (see references #1-2 below). This, of course would be catastrophic for vulnerable coastal cities for both livability but initially for any places already exposed to storm surges. New York City is one most at risk.


Sea level rise has also been locally enhanced along the Northeast US Coast because of abnormally warm waters building offshore for years, leading to increased thermal expansion of the water surface upward. This may also be a result of climate change-induced weakening (#3) of the Atlantic Meridional Overturning Circulation (AMOC). While Superstorm Sandy wasn’t “caused” by climate change, it was part of an increasing regime of more extreme weather events (and events with with more extreme hazard variables) and a prelude to what will be far more frequent in the coming decades.

Sandy was retired after the 2012 Hurricane Season, causing 233 deaths from the Caribbean to the United States and producing an incredible $75 billion in damages (only 2nd to Hurricane Katrina). An incredible and devastating meteorological event which we can hope we continue to recover from and our country will be better prepared to mitigate against next time.

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Surface analysis at 5 pm EDT October 29, 2012 showing Superstorm Sandy just offshore the coast of New Jersey pounding the Mid-Atlantic to New England. The intense pressure gradient (shown by the isobars) caused areas of gale and storm force winds over the Great Lakes because of the expanse of the storm.
Scientific References (for the nerds like me!):

1- Hansen et al. 2016. (scientific technical)

2- New science suggests the ocean could rise more — and faster — than we thought (Washington Post/Oct 17)

3. Youtube video of conference presentation (2016) by Dr. Stefan Rahmstorf on weakening AMOC. Can also refer to (#1) on this issue as it relates to potential effect on ice sheet dynamics.

Hurricane Ophelia Undergoing Extratropical Transition as it races for Ireland and the UK

Update at 6:50 pm CDT Sunday:

Ophelia appears to have nearly completed the process to Post-Tropical based on satellite imagery, with the whole arrangement of frontal boundaries and more asymmetric wind field and lack of any significant tropical characteristics outside of some convection (thunderstorm activity) northeast of the center. Ophelia is still a hurricane-force cyclone (likely top sustained winds 75-85 mph) and impacts still expected to quickly increase over Ireland Monday morning with rain, damaging winds and dangerous surf and coastal flooding.

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Hurricane Ophelia…at least it was still considered one at 11 am AST…is quickly transitioning to a hybrid post-tropical cyclone. I made up a schematic using current infrared satellite imagery. You can clearly see the transitioning hurricane becoming surrounded by cold, dry air on its’ back side, with its own warm, moist tropical air mass contributing to warm air advection ahead of it. And you can the developing frontal structure…cold front developing offshore Portugal and warm frontal cloud structure fanning out far to the north of the low center and offshore Ireland. The cyclone itself should be fully post-tropical in the next few hours, if it can’t be considered so already. Impacts (moderate to heavy rain and damaging winds) begin their arrival  Monday morning. My forecast for Ireland (written last night) can be found HERE.

Surreal view…a major hurricane near Western Europe.

Incredible views today…

Hurricane Ophelia set two records: 1) The highest latitude major hurricane on record in the North Atlantic Basin, set beginning at 35.9 N and 2) the most easterly major hurricane on record in the basin, set beginning at 26.6W. It will likely weaken below major hurricane force by Sunday morning as it begins to undergo transition into a frontal cyclone from its interaction with the jet stream and further reduction of sea surface temperatures below 72 degrees F/22 degrees C. However, it will be one for the record books.

Fortunately, Ireland and the United Kingdom will not need to worry about a major hurricane hitting them. They will need to worry about a likely damaging windstorm from a post-tropical hybrid cyclone. The post-tropical incarnation will develop frontal characteristics as it initially weakens, but its strong inner warm-core will continue to release some heat into the system, re-intensifying it as it becomes fully embedded in the mid-latitude westerlies and races into Ireland and the UK Monday afternoon and evening. My updated forecast for Ireland is below. Still expecting winds capable of downing trees and causing major power disruptions. The forecast for intense winds is high in confidence as computer models hone in on the center of the storm either coming ashore the southern tip of Ireland or just grazing the western shore. This is favorable for a “big blow” over the entire island. Residents need to be prepared to stay indoors and stay safe during the day Monday.

Ireland Forecast for Post-Tropical Cyclone Ophelia:

 

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Forecast zones (North and South) used for my forecast.

 

Monday Morning (After 7 am local time): For the southern half of the island, wind gusts of 40-50 mph (64-80 km/h) will develop during the morning, increasing to 60-85 mph (97-137 km/h) by mid to late morning from the coast, northward. The strongest gusts will be along the coastal areas, especially the south shores where isolated gusts may approach 100 mph (161 km/h). For the northern half of the island, wind gusts to 40 mph will develop mid morning , increasing to 50-60 mph late morning, from south to north.

Monday Afternoon (After noon): For the south, wind gusts of 60-85 mph (97-137 km/h) early afternoon with isolated to 100 mph/161 km/h along the south/southeast shores). For the north, wind gusts of 50-60 mph (80-97 km/h) early afternoon will increase to 60-85 mph by mid afternoon with isolated gusts to 100 mph along the northeast shores, spreading from south to north into the late afternoon.

Monday Night (after 5 pm local time): For the south, wind gusts will gradually decrease to 40-55 mph (64-89 km/h) during the early evening from south to north. For the north, wind gusts will gradually decrease to 40-55 mph during the mid to late evening (after 7 pm) from south to north.

Sea conditions will be hazardous all around Ireland with wind gusts in excess of 100 mph (161 km/h) likely in the south coastal waters and in the Irish Sea.

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High-resolution Swiss model showing the tightly-packed circulation of then Post-Tropical Cyclone Ophelia reaching coastal Ireland midday Monday. Damaging winds will be spreading throughout the Irish Republic and Northern Ireland by this time. Shown for illustration of the overall forecast scenario.

Hurricane Ophelia now a very rare Category 3 storm south of Azores

Hurricane Ophelia has strengthened into a Category 3 hurricane with maximum sustained winds of 115 mph as it moves south of the Azores. It is moving over prime atmospheric conditions, even as it overcomes waters of only 25 degrees C/77 degrees F. In normal tropical environments, tropical cyclones need water temperatures of 26 degrees C/79 degrees F to maintain themselves and warmer to significantly strengthen. However, the colder temperatures in the upper-atmosphere associated with the mid-latitude troposphere is providing Ophelia with ample atmospheric instability (warm, moist air rising into cold air aloft intensifying thunderstorm activity). In addition, mid-latitude dynamics are playing a role…the approaching frontal system and associated upper-level trough of low pressure approaching Ophelia is giving the system a “poleward outflow jet” to pull air away from the system and allow the surface low to strengthen.

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Meteorological Analysis of Category 3 Hurricane Ophelia. Favorable dynamic and thermodynamic set up allowing system to strengthen at high latitude, over cooler waters for hurricane maintenance. With that said, water temps under Ophelia are running 2-3 degrees C above normal, also allowing it to have its unusual intensity near Western Europe.

See my previous post from late last night for my wind forecast for Ireland. Strong winds should begin to impact the island midday Monday (local time), with stormy conditions lasting into Monday night. The southeastern Azores will see some gusty winds and 1-3 inches of rain as it passes by this evening and night.

–Meteorologist Nick Humphrey