Emergence of Arctic Extremes

: Recent increases in extreme events, especially those near and beyond previous records, are a new index for Arctic and global climate change. They vary by type, location, and season. These record-shattering events often have no known historical analogues and suggest that other climate surprises are in store. Twenty-six unprecedented events from 2022, 2023, and early 2024 include record summer temperatures/heatwaves, storms, major Canadian wildfires, early continental snow melt, Greenland melt, sea temperatures of 5–7 ◦ C above normal, drought in Iceland, and low northern Alaskan salmon runs. Collectively, such diverse extremes form a consilience, the principle that evidence from independent, unrelated sources converge as a strong indicator of ongoing Arctic change. These new behaviors represent emergent phenomenon. Emergence occurs when multiple processes interact to produce new properties, such as the interaction of Arctic amplification with the normal range of major weather events. Examples are typhon Merbok that resulted in extensive coastal erosion in the Bering Sea, Greenland melt, and record temperatures and melt in Svalbard. The Arctic can now be considered to be in a different state to before fifteen years ago. Communities must adapt for such intermittent events to avoid worst-case scenarios.


Introduction
Emergence occurs when a complex entity has properties or behaviors that its parts do not have on their own, and emerge when they interact as a wider whole; emergence concerns new properties of a system.The physical state of the Arctic (atmosphere, ocean, sea ice, and land) can now be considered as a different state to before fifteen years ago, based on the emergence of environmental extremes that are beyond previous records.Classically, tracking the state of the Arctic follows Arctic-wide or regional temperature increases, permafrost thaw, and year-to-year losses in sea-ice extent.Now, individual Arctic extremes are often record-shattering [1][2][3].Such extremes represent new major indicators of climate change, as they show conditions beyond previous observations [4].They are beyond those of temperature increases projected by climate models; such models may not resolve the interaction of physical and ecological processes due to inadequate spatial resolution and lack of sufficient process interactions.These new states cannot easily be assigned occurrence probabilities because they have no historical analogues.Arctic changes are statistically nonstationary.Recent extremes suggest that other Arctic climate surprises may be in store.It is far from obvious how to even pose the question of the future states.We look beyond trends to the increasing collection of extreme events.
Such events vary in type, location, and season.For example, Thoman et al. [5] reported six major recent Arctic extreme events that occurred during summer 2023: summer air temperatures shattering records, early continental snow melt, unprecedented Canada wildfires, Greenland snow melt, Barents, Kara, Laptev, and Beaufort Seas temperatures of 5-7 • C above normal in August, and extreme low northern Alaskan salmon runs.These multiple types, and additional Arctic data, form a consilience, the principle that evidence from independent, unrelated sources can converge on strong conclusions.That is, when multiple sources of evidence agree, the conclusion for change is strengthened.The Arctic emerges as being in a physical state beyond previous indicators and processes, and these multiple Arctic changes serve as an indicator of global change.Such consilience is shown by a compilation of recent observations.The term extreme event is understood in one of two ways, based on how rare it is compared to the past, or based on how large the impacts are.One approach to uncertainty is resolvable based on probability distributions.Formally, the distribution can be generated from historical data or model simulations.Climate change can have different effects on the probability of extreme values of the distribution.For example, a simple shift of the entire distribution toward a warmer climate leads to fewer extreme cold weather events and more hot weather and extreme hot weather events.Alternatively, increased temperature variability without a shift in the mean could lead to more extreme cold and heat events, with lower probability of mid-range temperature events.At the opposite pole of uncertainty from historical randomness are genuine unknown unknowns, termed radical uncertainty.These are states to which one cannot attach probabilities because one cannot a priori conceive of these states.They often have no historical analogue situations.They are not likely to be the result of a long tail event arising from a low-probability outcome from a known frequency distribution, but as a result that was not previously expected.The probability distribution approach has dominated decision science.In fact, statistical extrapolation methods do not conceivably have the information required to specify their future distribution of events, and consequences are uncertain.An alternative is to plan for outcomes that are better and avoid outcome that are worse.Many aspects of climate science are in this situation of having a low amount of prior knowledge, and being comparatively data-poor in terms of what is actually attempted to be predicted.The observed record provides only a limited sample of what is possible, and is, moreover, affected by nonstationarity.
The future is, thus, inherently unpredictable, especially after rare events that are beyond previous records.Given the short record of events of the last half decade and their contrast with earlier years, statistical tests are less useful.Going forward depends on rationality and logic.Information is incomplete; there is limited prior knowledge available to make future projections.Using statistical methods that lack physical reasoning and prior knowledge-"letting the data speak for itself"-is a pathway for disaster [6].An alternative is to continue observations, scenario building, and plan to avoid negative outcomes.

Data Sources
Extreme events in the Arctic are noted by [1,3,7,8].Updates through 2022 and 2023 are given by Benestad et al. and Thoman et al. [5,9].Overland [8] included 2017-2022 records from the Local Environmental Observer (LEO) Network that are provided by a solicited group of observations from local residents, news articles, and topic experts; in addition to weather, they note species declines and changes in species range.Benestad et al.'s [9] 2022 summary is based on an inquiry collection contributed from meteorological services connected to the Arctic.The number of recorded events for 2022 was sixty-eight.Examples were summer heatwaves in Greenland, Finland, Svalbard, Iceland, Alaska, and Canada.There were rain events in Alaska and Norway and low sea ice in Russia in March.There were cold events in Russia and the Yukon in December.Not all events set new records.Typhoon Merbok in September 2022 had northwest Pacific Ocean temperatures enhancing the storms strength, and it further propagated through the Bering Sea, impacting Alaskan shorelines.A summary of unprecedented weather extremes is provided in Table 1, showing 26 major events in 2022, 2023, and early 2024.The events noted by Thoman et al. [5] are verified by the Arctic Regional Climate Centre network (ArcRCC) Arctic Climate Forum (ACF), and the Table is updated through the ArcRCC Fall 2023 and Spring 2024 Reports.

Emergence through Natural Weather Variability Interacting with Arctic Amplification
A conceptual model ties slow and fast timescale processes into joint causal accounts [8].Many new extremes affecting ecosystems and communities are forced by the interaction of atmosphere, ocean, and other Arctic changes.Fluctuations can result in impacts outside of resilience boundaries.The conceptual model in Figure 1 combines ongoing natural weather events, with global warming/Arctic amplification (AA, temperature increases, loss of sea ice and permafrost) from greenhouse gases increases-a thermodynamic response (a push).A natural range of atmospheric and oceanic dynamics (a pulse), e.g., blocking weather patterns, storms, jet stream meanders, and upper ocean heat content, provides an enhancement to the AA push, resulting in new extremes.AA provides the regional precursors for major extreme impacts.The result is a large number of types and seasonal and regional differences of extreme events.Ecosystem and human impacts result from weather and climate extremes, such as the timing of species reproduction and migration.

Greenland Snow Loss as an Example of Atmospheric Events Combining with Arctic Amplification
The interaction of atmospheric circulation anomalies with the surface mass balance

Greenland Snow Loss as an Example of Atmospheric Events Combining with Arctic Amplification
The interaction of atmospheric circulation anomalies with the surface mass balance of the Greenland ice sheet is an example of an application of the conceptual model and emergence, of relevance for Greenland's contribution to sea level rise [10].Unprecedented atmospheric conditions relative to 1948-2018 occurred in the summer of 2019 over Greenland, promoting new record or close-to-record values of surface mass balance, runoff, and snowfall.The connection of higher atmospheric 500 hPa geopotential heights over Greenland representing stronger southerly winds, and glacial runoff representing melt, has a correlation of 0.85, with 2019 providing a major example (Figure 2A,B).Summer 2019 was characterized by the persistence of large-amplitude jet stream meanders with changed storm tracks and reduced snowfall that enhanced melt.The summer atmospheric 500 hPa geopotential height pattern from 2019 was five standard deviations above its 1981-2010 mean.Figure 2A shows a high correlation between runoff as a proxy for melt, and the strength of the atmospheric weather pattern (year 2019 in red dot).Figure 2B shows the summer 2019 air temperature response.Further, in August 2021, the Greenland Summit station had rainfall for the first time [11,12], accompanied by extensive surface melt.As in 2019, meteorology contributed to 2021 conditions through a storm track route referred to as an atmospheric river (AR), contributing heat transfer from condensation and air temperature advection.The frequency of ARs reaching Greenland is increasing [13], driven by south-north-oriented jet-stream Further, in August 2021, the Greenland Summit station had rainfall for the first time [11,12], accompanied by extensive surface melt.As in 2019, meteorology contributed to 2021 conditions through a storm track route referred to as an atmospheric river (AR), contributing heat transfer from condensation and air temperature advection.The frequency of ARs reaching Greenland is increasing [13], driven by south-north-oriented jet-stream patterns [14].Following in September 2022, exceptional heat and rainfall occurred from a series of atmospheric transport events from the south [15].Temperatures in September were the highest on record, up to 8 • C higher than average.The ice sheet saw record melting, with 23% of its area impacted [15].

Bering Sea Ecosystem and Sea-Ice Loss
An unprecedented event was extreme sea-ice minimums during winter 2018 and 2019.Sea-ice loss events initiated a series of marine environmental and ecological changes through a connected chain of events though southerly winds and warmer temperatures [16].Ecological shifts were a reorganization of the regional Bering Strait marine ecosystem, with impacts on coastal communities.In the years after 2021, the Bering Sea has returned to more typical climate conditions, highlighting the intermittency of such extremes going forward.Even though low sea ice will not occur every year, residents are on notice of possible reoccurrence of extreme low sea ice and warm temperature years over the next decades with ecological and societal impacts.

Temperatures in Northern Svalbard
The average June 2022 temperature at Svalbard Airport Longyearbyen was 6.0 • C, which is 2.4 • C above average and the warmest ever recorded [17].The warming is linked, in both space and time, to the reduction in Barents Sea sea ice and increased sea surface temperature (SST); there is a negative correlation between surface air temperature (SAT) and sea ice at multiple meteorological stations of −0.94 in autumn and −0.97 in winter.The northern Barents Sea highlights high temperatures of the 21st century, with a warming rate that is greater and longer lasting than during the earlier 20th-century warming.Figure 3 shows the spatial distribution of the annual rate of temperature change for the Barents Sea during 2001-2020 for two atmospheric reanalyzes of SAT [18].A factor for warm temperatures in northern Svalbard was the increased presence of low sea-level pressure over the north-central Barents Sea combined with the long-term SAT warming trend (Figure 3), which cause easterly warm winds to the north of the low-pressure center.Northeasterly wind circulation contributes the most to extreme Svalbard warming [17].A significant pulse of warm air starting on 15 July 2022 produced Svalbard's highest recorded melt volume on 17 July.Temperature measurements taken at Svalbard Airport from June, July, and August show that the Arctic Archipelago experienced a record hot summer in 2022.

Typhoon Merbok
The remnants of typhoon Merbok impacted western Alaska on 17 September 2022.Ocean waves reached 15 m in the Bering Sea and storm surge water levels at Nome, Alaska, were 3.2 m, the largest since November 1974 (Figure 4) [19].A 1000-mile shoreline of Alaska's west coasts from Bristol Bay to beyond Bering Strait were impacted.Merbok formed in the northwest Pacific Ocean.There were extreme sea temperatures, with Merbok traveling over waters on the Russian side of the Bering Sea that were the warmest on record going back nearly 100 years.With warmer ocean water there is more evaporation moisture entering into the atmosphere that feeds the energy of the storm.Merbok was the strongest storm that has occurred in autumn.There have been stronger storms but they typically occur in October and November.Later in the season, sea ice can provide some protection to coastal shores, but in September, a full wave action and storm surge impacted the coast.The main new features of Merbok were the early season occurrence and the warm Pacific Ocean/western Bering Sea sea temperatures.
the north-central Barents Sea combined with the long-term SAT warming trend (Figure 3), which cause easterly warm winds to the north of the low-pressure center.Northeasterly wind circulation contributes the most to extreme Svalbard warming [17].A significant pulse of warm air starting on 15 July 2022 produced Svalbard s highest recorded melt volume on 17 July.Temperature measurements taken at Svalbard Airport from June, July, and August show that the Arctic Archipelago experienced a record hot summer in 2022.

Typhoon Merbok
The remnants of typhoon Merbok impacted western Alaska on 17 September 2022.Ocean waves reached 15 m in the Bering Sea and storm surge water levels at Nome, Alaska, were 3.2 m, the largest since November 1974 (Figure 4) [19].A 1000-mile shoreline of Alaska s west coasts from Bristol Bay to beyond Bering Strait were impacted.Merbok formed in the northwest Pacific Ocean.There were extreme sea temperatures, with Merbok traveling over waters on the Russian side of the Bering Sea that were the warmest on record going back nearly 100 years.With warmer ocean water there is more evaporation moisture entering into the atmosphere that feeds the energy of the storm.Merbok was the strongest storm that has occurred in autumn.There have been stronger storms but they typically occur in October and November.Later in the season, sea ice can provide some protection to coastal shores, but in September, a full wave action and storm surge impacted the coast.The main new features of Merbok were the early season occurrence and the warm Pacific Ocean/western Bering Sea sea temperatures.

Consilience and Emergence from an Arctic Dataset
The evidence for consilience is provided by Table 1.It shows 26 unprecedented weather events during 2022, 2023, and early 2024.Although I cannot provide an earlier comparison baseline for extreme events, the sources for Table 1 note their unprecedented nature.Such events tend to be short-lived, occur in multiple regions, and are multivariate.Arctic data meet the criteria for both emergence and consilience.Consilience is the principle that evidence from independent, unrelated sources can converge on a strong conclusion.That is, the conclusion for Arctic change is strengthened.Emergence occurs when a

Consilience and Emergence from an Arctic Dataset
The evidence for consilience is provided by Table 1.It shows 26 unprecedented weather events during 2022, 2023, and early 2024.Although I cannot provide an earlier comparison baseline for extreme events, the sources for Table 1 note their unprecedented nature.Such events tend to be short-lived, occur in multiple regions, and are multivariate.Arctic data meet the criteria for both emergence and consilience.Consilience is the principle that evidence from independent, unrelated sources can converge on a strong conclusion.That is, the conclusion for Arctic change is strengthened.Emergence occurs when a complex entity has properties or behaviors where its parts interact as a wider whole, such as AA with natural meteorological and oceanographic variability.Based on the range of extreme events shown in this and earlier papers, the Arctic emerges as being in a physical state beyond previous indicators.These multiple Arctic changes also serve as an indicator of global change.Some changes represented by events are nearly complete, such as the Atlantification of the Barents Sea, e.g.warming, salinification, and longer-term ecosystem shifts due to temperature increases.Most Arctic regions are subject to intermittent events.Unpredictable, unprecedented behaviors are seen as emergent phenomena.
The use of emergence here is meant as a system change based on a new set of environmental extremes.It differs from some previous uses of the term by Arctic scientists.These authors use the term emergence in the context of Arctic amplification to mean that the anthropogenically forced surface temperature signal is larger than the noise from internal variability [20,21], which is different to saying that the Arctic has fundamentally new behavior.

Impact-Based Projections
The increase in future uncertainty due to lack of robust extrapolation does not mean that planning is less important.For adaptation, a way forward to future extremes is through scenario/narrative approaches [6].For example, proposed impacts on the ecosystem are extrapolated backwards through species life histories to identify causal factors for change (e.g., temperature, storms, sea ice, permafrost).Such impacts could include wildfires, flooding, ecosystem shifts, biological pests, change in snow water equivalent, storm intensity, fisheries, and marine mammals' seasonal life histories.Such approaches emphasize the identification of potential major impacts and their causes, and strategies that are adaptable and robust.Such approaches should include equitable and ethical engagement of Indigenous Peoples and Indigenous Knowledge.

Summary
The latest IPCC assessment determined that "It is unequivocal that human influence warmed the atmosphere, ocean and land".Particularly for large-scale changes, there are robust anthropogenic signals that have been identified through multiple lines of evidence.Accompanied by a rapid loss of Arctic sea ice in recent decades, the winter Arctic has warmed three times faster [22,23] than the global mean, based on observed data since 1980 [24].In addition to these trends, multiple unprecedented extreme events now add valuable, additional information to the climate change story.Thus, when the natural range of meteological variability is combined with AA, they provide a mechanism for unprecedented Arctic extremes.
Listed are a collection of recent extreme events in the Arctic during recent years (Table 1).Arctic data meet the criteria for consilience of Arctic change.Most Arctic regions are now subject to intermittent extreme events.The recent emergence of new states is different for previous climatology, with unpredictable behavior.The observed record provides a limited sample of what is possible, and recent observations are manifestly nonstationarity.
Moving forward, information necessary to guide communities for adaptation responses requires continuing monitoring every year, physical reasoning, and judicious use of existing process knowledge.It is important to adopt policies and strategies that are robust to alternative futures.Such futures cannot be calculated, only framed by identifying critical impacts and applying a sense of how these factors have interacted in the past and might interact in the present and future, undertaking planning to avoid worse outcomes.

9 Figure 1 .
Figure 1.Conceptual model of extremes combines Arctic amplification interacting with internal atmosphere and ocean processes that then can impact ecosystems.Reprinted from [8].

Figure 1 .
Figure 1.Conceptual model of extremes combines Arctic amplification interacting with internal atmosphere and ocean processes that then can impact ecosystems.Reprinted from [8].

Figure 2 .
Figure 2. (A) Correlation of the 500 hPa pressure pattern over Greenland, with the runoff as a proxy for snow melt.Modified from Tedesco and Fettweis [10].The red dot is the 2019 data point.(B) 2 m air temperatures obtained from the MAR model forced by the reanalysis NCEP/NCAR reanalysis for June-August 2019.Reprinted from Tedesco and Fettweis [10].

Figure 2 .
Figure 2. (A) Correlation of the 500 hPa pressure pattern over Greenland, with the runoff as a proxy for snow melt.Modified from Tedesco and Fettweis [10].The red dot is the 2019 data point.(B) 2 m air temperatures obtained from the MAR model forced by the reanalysis NCEP/NCAR reanalysis for June-August 2019.Reprinted from Tedesco and Fettweis [10].

Figure 3 .
Figure 3.The spatial pattern of changes in surface air temperature in the Barents Sea area for 2001-2020 [18].(c,f) Annual SAT trends (°C/decade) derived from CARRA and ERA5 reanalysis.Reprinted from [18].

Figure 3 .
Figure 3.The spatial pattern of changes in surface air temperature in the Barents Sea area for 2001-2020 [18].(c,f) Annual SAT trends ( • C/decade) derived from CARRA and ERA5 reanalysis.Reprinted from [18].Climate 2024, 12, x FOR PEER REVIEW 7 of 9

Figure 4 .
Figure 4. Typhoon Merbok spins off the Alaskan coast.Credit: NOAA National Weather Service.

Figure 4 .
Figure 4. Typhoon Merbok spins off the Alaskan coast.Credit: NOAA National Weather Service.

Funding:
NOAA Arctic Research Program, Global Ocean Monitoring and Observing.Data Availability Statement: Data available from referenced sources.

Table 1 .
List of unprecedented weather events in 2022, 2023, and early 2024.