Precipitation trends

[sidd]

We expect increase in precip intensity due to anthro climate change. An Australia-wide study sees storms shrinking in both area and duration together with increases in peak rainfall rate.

doi:  10.1002/2016GL068509

A previous study by some of the same authors is at

DOI: 10.1038/NGEO2456

This will stress stormwater systems leading to more frequent flooding, an especial concern to coastal and floodplain infrastructure. Weather models are not (yet ?) good enuf to model these effects, and i doubt they will improve very quickly.

[abbottisgone]

 I am in Perth and we talk about long term trends of decreasing rainfall patterns in the Southwest of Western Australia.

 This must be simply a peculiarity to our little bit of Australia, is that correct?

[sidd]

i think the paper argues that it rains in smaller areas for shorter times but with greater intensity. I dont think it says much about total rainfall.

[sidd]

Realclimate has a post on climate signals, and a reference to a very useful (open access) paper by Benestad on precipitation trends. He finds that the total area where precipitation occurs has shrunk

"A linear trend analysis indicates a change in the estimated rainfall area from 25% to 23% over the 1998–2016 period. The trend is statistically significant at the 1% level."


The total atmospheric water content remained approximately constant over 1998-2016 according to the ERA-Interim, whereas the global mean rate of evaporation increased from 1400 to 1500 giga-tons (table 1). The total 50 ◦ S–50 ◦ N precipitation increased slightly from 1122 giga-ton/day to1152 giga-ton day −1 according to the TRMM data and 1300–1308 giga-tons according to ERA-Interim "

The odd part is we see from the supplementaries that total precipitation has remained constant over land, but increased over ocean. Very intersesting paper. Read the whole thing.

doi: 10.1088/1748-9326/aab375

sidd

[Alexander555]

If China creates more rain, is there not going to be a place that will get less rain ?

http://www.scmp.com/news/china/society/article/2138866/china-needs-more-water-so-its-building-rain-making-network-three

[mitch]

On China rain--by the time that the air mass gets to the Tibetan Plateau there is basically no way to add much additional water vapor. If the cloud seeding actually works, which I question, it will dry the air mass and make it less likely to rain downstream. However, this dry air mass will be interacting with wet ones coming from off the ocean over China. 

Ultimate answer is that it is complicated to what extent it will affect rainfall in other regions.

[bligh8]

It’s a hard rain that’s fallen…
Note in the first graph there’s no upper limit,  just grater than 75%
Half or more of the Ocean beaches are under caution for high level of bacteria.
The run off has turned the Ocean brown for what appears to be several miles to seaward.

[vox_mundi]

Researchers Find Precipitation Thresholds Regulate Carbon Exchange

... Our results suggest that the short-term carbon balance of ecosystems may be more sensitive to respiration losses than previously thought and that model simulations may underestimate the positive carbon–climate feedbacks associated with respiration.

... Ecosystems either soak up carbon through photosynthesis—a negative feedback that could reduce future warming—or release it through respiration—a positive feedback that could enhance future warming. Understanding how climate change might impact ecosystem photosynthesis and respiration is critical for predicting future carbon dynamics.

Liu's team discovered that whether ecosystems across the U.S. uptake carbon or release it is dependent on water availability. The primary control switches from production to respiration at an annual precipitation threshold between 30 and 35 inches in the contiguous United States. The carbon balance of ecosystems in the dry West is very sensitive to photosynthesis. In contrast, the carbon balance of more mesic Eastern U.S. ecosystems is more sensitive to carbon lost through respiration.

However, climate models do not reflect this precipitation threshold. Liu and his co-authors determined that these models are far too sensitive to photosynthesis and not sensitive enough to respiration, suggesting the Earth's ecosystems may lose more carbon to the atmosphere in the future as surface temperatures continue to warm.

"This study suggests we know more about the negative feedback loop and less about the positive one."

Zhihua Liu et al, Precipitation thresholds regulate net carbon exchange at the continental scale, Nature Communications (2018)

[bligh8]

Older homes in this area NJ were built with porous cinder block, these changing rainfall patterns dry/very wet are contracting expanding the Marlboro clay substrate, changing the static pressure loads on  home foundations = Step cracking then horizontal cracking….a new industry has come alive….vertical carbon fiber straps epoxied to foundation walls in an effort to stabilize the walls.  It el work for a while…. maybe.

[sidd]

Re: "vertical carbon fiber straps epoxied to foundation walls in an effort to stabilize the walls. "

This might need a different thread, but i doubt epoxy/carbon fiber. I have stabilized failing concrete block wall in basements in clay, and it takes large steel members, lots of digging and most important fix the drainage because it is hydrostatic pressure as well as clay swell/shrink that kills you. Sometimes pile driving is involved.

My experience with epoxy/carbon strap is that it mebbe ok above grade where you can see failure, but below grade moisture degrades the epoxy , and believe it or not, things eat away at it. Then it fails invisibly. But perhaps they have better and more toxic epoxy.

sidd

[TerryM]

The few times I've worked with expansive clay it seemed like a force of nature. I patched what I could & sold the house.
Terry

[johnm33]

In London I occasionally came across a house/terrace that had a land drain, remote [low mts.] from the buildings, that fed into a sump before discharging into the main drain. Usually a couple of feet below the clay the foundation brick courses were laid on. Unless they were damaged by trees they controlled the water table locally. These days a bore hole and pump might serve the same purpose.

[bligh8]

Re: "vertical carbon fiber straps epoxied to foundation walls in an effort to stabilize the walls. "

This might need a different thread, but i doubt epoxy/carbon fiber. I have stabilized failing concrete block wall in basements in clay, and it takes large steel members, lots of digging and most important fix the drainage because it is hydrostatic pressure as well as clay swell/shrink that kills you. Sometimes pile driving is involved.

My experience with epoxy/carbon strap is that it mebbe ok above grade where you can see failure, but below grade moisture degrades the epoxy , and believe it or not, things eat away at it. Then it fails invisibly. But perhaps they have better and more toxic epoxy.

sidd

Their installing these straps on basement interior walls (not mine).  I've installed 120ft of subsurface piping to carry water away from the house....so far, so good.  I meant to move this to 'Places becoming less livable"  hit the wrong button.  In Ocean Grove the 200 yr old homes have brick foundations using beach sand for mortar …..0pps.  They simply build new support walls using block inside the basement w/a false front.


bligh

[bligh8]

Re: "vertical carbon fiber straps epoxied to foundation walls in an effort to stabilize the walls. "

This might need a different thread, but i doubt epoxy/carbon fiber. I have stabilized failing concrete block wall in basements in clay, and it takes large steel members, lots of digging and most important fix the drainage because it is hydrostatic pressure as well as clay swell/shrink that kills you. Sometimes pile driving is involved.

My experience with epoxy/carbon strap is that it mebbe ok above grade where you can see failure, but below grade moisture degrades the epoxy , and believe it or not, things eat away at it. Then it fails invisibly. But perhaps they have better and more toxic epoxy.

sidd

Sidd...the carbon fiber straps were to be installed inside of the basement walls....but not by me.

This conversation belongs else ware…..but thanks.

bligh

[bligh8]

Overlooked Trends in Observed Global Annual Precipitation Reveal Underestimated Risks

Abstract....open access

Numerous human and environmental systems are sensitive to the spatial and temporal distribution of precipitation, including agriculture, water supply, and ecosystems. Trends in observed precipitation form an important line of evidence to understand how changes may increase system vulnerabilities. Linear trends reported in US and global climate assessments reflect changes in mean annual precipitation. Mean trends may not reflect changes across other quantiles in the precipitation probability distribution, including the tails (very high and low precipitation levels), leading to systematic mischaracterization of climate risk. Here we reanalyze global annual precipitation using quantile regression to reveal overlooked trends. We find trends in the tails inconsistent with the mean in 44.4% of land area and 40.7% of rainfed agricultural regions. Previously undetected trends offer a more accurate view of the changing climate. This work enables reappraisals of risk aggregated over thresholds in human and environmental systems, enabling revaluation of threats and identification of appropriate adaptation strategies.

https://www.nature.com/articles/s41598-018-34993-5

bligh

[Red]

Currently, half of the world's measured precipitation that falls in a year falls in just 12 days, according to a new analysis of data collected at weather stations across the globe.

By century's end, climate models project that this lopsided distribution of rain and snow is likely to become even more skewed, with half of annual precipitation falling in 11 days.
These results are published in Geophysical Research Letters, a journal of the American Geophysical Union.
Previous studies have shown that we can expect both an increase in extreme weather events and a smaller increase in average annual precipitation in the future as the climate warms, but researchers are still exploring the relationship between those two trends.


Read more at: https://phys.org/news/2018-11-world-annual-precipitation-falls-days.html#jCp

[bligh8]

I might imagine it's like this across much of New England.   The ground simply does not have the time between rain events to dry-out .. it's like walking on a wet sponge.

[bligh8]

>


The role of the permanent wilting point in controlling the spatial distribution of precipitation

https://www.pnas.org/content/115/22/5692#sec-1
Significance
One basic distinction between land and ocean is that the land can dry out. We show that this is of fundamental importance for the precipitation distribution over land as it brings precipitation from the precipitating region to the nonprecipitating region. This process prevents the land–atmosphere system from sustaining precipitation over the same region and thus acts against drought or the formation of desert. Paradoxically, although dry atmospheres are known to hamper moist convection, drying the soil to its permanent wilting point generates circulations that are strong enough to overcome this inhibition. Our findings help understand why tropical rain bands broaden poleward over land, the more so the drier the soils are.

Abstract
Convection-permitting simulations on an idealized land planet are performed to understand whether soil moisture acts to support or impede the organization of convection. Initially, shallow circulations driven by differential radiative cooling induce a self-aggregation of the convection into a single band, as has become familiar from simulations over idealized sea surfaces. With time, however, the drying of the nonprecipitating region induces a reversal of the shallow circulation, drawing the flow at low levels from the precipitating to the nonprecipitating region. This causes the precipitating convection to move over the dry soils and reverses the polarity of the circulation. The precipitation replenishes these soils with moisture at the expense of the formerly wet soils which dry, until the process repeats itself. On longer timescales, this acts to homogenize the precipitation field. By analyzing the strength of the shallow circulations, the surface budget with its effects on the boundary layer properties, and the shape of the soil moisture resistance function, we demonstrate that the soil has to dry out significantly, for the here-tested resistance formulations below 15% of its water availability, to be able to alter the precipitation distribution. We expect such a process to broaden the distribution of precipitation over tropical land. This expectation is supported by observations which show that in drier years the monsoon rains move farther inland over Africa.

Physically, the ability of soil moisture to store water and lose water in interaction with the atmosphere affects the partitioning between sensible and latent heat flux and through this the precipitation distribution in two potentially opposing ways. First, a change in the Bowen ratio affects the stability of the atmosphere and hence the triggering of convection. The most common response is that an increase in soil moisture favors the triggering of convection (18, 19) and hence increases precipitation. Following this argument, soil moisture maintains precipitation in the precipitating region. Second, the spatially localized nature of convective precipitation leads to the development of soil moisture gradients. Gradients in soil moisture lead to gradients in sensible heat flux, which can thermally induce a shallow circulation with surface flow from the wet to the dry region. This circulation can lead to the triggering of convection over the dry region (20, 21), a phenomenon that has been in particular observed in the Sahel region (22), although its signature has been deciphered globally (23). Following this second argument, soil moisture brings precipitation to the nonprecipitating region.

The below are all extracts from within the paper.


Soil Moisture Brings Precipitation to the Nonprecipitating Region
We use a simple formulation for the land surface in our simulations, a formulation that retains the two key characteristics of soil moisture (Materials and Methods): its spatial and temporal variability through the action of precipitation and evaporation as well as its nonlinear control on the surface fluxes via the use of a resistance formulation (Eq. 5). This model version is compared with a version where the soil moisture resistance is set to zero, mimicking the situation of an infinite supply of water.
In our simulations, convection rapidly develops and produces precipitation with a daily mean of around 4.6 mm⋅d−1. The spatial distribution of precipitation (Fig. 1) indicates that in both model versions convection organizes as time proceeds. That convection spontaneously begins to self-aggregate into a large convective structure is a well-known feature from past RCE simulations, as noted previously. Interactive soil moisture leads to little difference between the simulations up to around day 60. The monthly mean precipitating area, calculated from days 25 to 55, occupies 76% of the domain in both simulations. Hence, during this time period, the precipitation distribution is fully controlled by the atmosphere. This is consistent with values of the atmospheric resistance rara that are much larger than values of the soil moisture resistance rsrs, for instance 100 times larger at noon.

The Spatial Distribution of Precipitation Is Fully Determined by Shallow Circulations
We investigate the processes determining the spatial distribution of precipitation, in particular those leading to its homogenization by soil moisture. We focus on the simulation with interactive soil moisture around day 60.
The self-aggregation of convection, before day 60, is due to a shallow circulation (Fig. 2A) that spins up in the boundary layer due to the distinct radiative heating profiles of the nonprecipitating and the precipitating region
The circulation maintains the convection aggregated in one band with minimal changes in direction (Fig. 3A). Around day 60, however, the circulation pattern drastically changes and begins to converge into the previously nonprecipitating region (Figs. 2B and 3A), called the desiccated region.



Following the altered circulation pattern, precipitation starts falling on the desiccated region of the domain around day 60 (Figs. 2 and 3) and the two circulation forcings work hand in hand. As the precipitation replenishes the soil moisture, the surface forcing disappears in less than 10 d (Figs. 2 B and C and 3C). The radiatively driven circulation nevertheless maintains the new precipitation distribution until dry enough areas form in other parts of the domain and steal the precipitation (Fig. 2 C and D). This results in a permanent back and forth between the radiatively driven circulation, which wants to organize the convection in one place, and the soil moisture-induced circulation, which wants to disorganize the convection

Summary
Letting radiation, convection, and soil moisture interact with each other in an initially homogeneous land–atmosphere system indicates that the fundamental role of soil moisture is to bring precipitation from the precipitating to the nonprecipitating region.

much more within paper…..which I assume is still dry.

[vox_mundi]

The 3 Highest-Volume U.S. Rainfall Events on Record Have Happened in the Past 3 Years
http://www.desdemonadespair.net/2018/12/the-three-highest-volume-us-rainfall.html
https://www.wunderground.com/cat6/3-Highest-Volume-US-Rainfall-Events-Record-Have-Happened-Past-3-Years

Preliminary research by precipitation expert Dr. Kenneth Kunkel of the North Carolina Institute for Climate Studies, announced in September, found that the three highest-volume rainfall events in the U.S. in the last 70 years have occurred since 2016: Hurricane Harvey in Texas/Louisiana in 2017, Hurricane Florence in North Carolina in 2018, and a March 2016 storm in Louisiana. It is highly unusual to get three such extreme events in one three-year period, and the odds of this occuring were increased by global warming, which boosts the amount of water vapor in the air and increases the frequency and intensity of heavy precipitation events.

Dr. Kunkel’s ratings were based on four-day rainfall totals over an area of 14,000 square miles (an area 40% larger than the state of Maryland). Harvey delivered an average of 25.6 inches of rain over an area of 14,000 square miles, while Florence was a somewhat distant second place, with an average of 17.5 inches of rain over a like-sized area.



See the top 10 ...

[bligh8]

https://phys.org/news/2018-12-global.html

The long dry: global water supplies are shrinking


"A global study has found a paradox: our water supplies are shrinking at the same time as climate change is generating more intense rain. And the culprit is the drying of soils, say researchers, pointing to a world where drought-like conditions will become the new normal, especially in regions that are already dry.


"The study – the most exhaustive global analysis of rainfall and rivers – was conducted by a team led by Professor Ashish Sharma at Australia's UNSW (University of New South Wales) in Sydney. It relied on actual data from 43,000 rainfall stations and 5300 river monitoring sites in 160 countries, instead of basing its findings on model simulations of a future climate, which can be uncertain and at times questionable.


'Blue water' vs 'green water'


"For every 100 raindrops that fall on land, only 36 drops are 'blue water' – the rainfall that enters lakes, rivers and aquifers – and therefore, all the water extracted for human needs. The remaining two thirds of rainfall is mostly retained as soil moisture – known as 'green water' – and used by the landscape and the ecosystem.
As warming temperatures cause more water to evaporate from soils, those dry soils are absorbing more of the rainfall when it does occur – leaving less 'blue water' for human use.
"It's a double whammy," said Sharma. "Less water is ending up where we can store it for later use. At the same time, more rain is overwhelming drainage infrastructure in towns and cities, leading to more urban flooding."

[Sigmetnow]

Africa's Sahel belt has experienced a 50-percent hike in record dry months in recent decades
http://news.trust.org/item/20181213131425-l9z76/

[TerryM]

A few very basic questions.


As a volume of air is heated it expands though mass remains constant.
If we began at 50% humidity, then heated our mix, the mass of water vapor remains constant even as the volume of air and water vapor increase and the humidity index drops.
As humidity drops the delta between wet bulb and dry bulb temperature increases.


If no water is added to or precipitated from or mix, can the dry bulb temperature ever drop simply as the result of heating the atmosphere?
If we began with fully humidified air, (100% humidity), wet bulb temperatures must be equal to dry bulb temperatures prior to heating.
If we began with fully desiccated air, (0% humidity), the delta between wet and dry bulb temperatures is already maximized prior to heating.


100% humidity air must produce the greatest possible delta between wet and dry bulb temperatures after heating.


Would heating a 0% humidity atmosphere by 1C raise the dry bulb temperature by 1C.


If our experiments took place over open water, would atmospheric humidity remain ~constant due to increased evaporation?


I managed to work out some of my questions merely by writing them down.


Thanks
Terry

[Sebastian Jones]

I love your questions Terry!
In my experience, wet bulb temps are more useful for describing how the air feels than for describing the amount of heat in the air. Therefore, no, dry bulb temperature could not fall as the temperature rises....but it might feel that way! We feel the opposite when the temperature is dropping in winter- because the amount of water vapour remains constant, the relative humidity rises as the temperature falls and it feels colder than it really is....I think!

[mitch]

My experience in College Station Texas:  At night in summer the air would cool down nearly to the dewpoint, about 70 deg F, so would be near 100% relative humidity.  Late afternoon the temperature would be around 103 deg F, and the relative humidity would be about 30%. The air was fed from the Gulf of Mexico, so there was plenty of water vapor.

[Sleepy]

Stumbled over these two beautiful precipitation animations:
https://twitter.com/Climatologist49/status/1125790157284696065

Added below (optimized for size, sorry mac users).

[bligh8]

Position and orientation of the westerly jet determined Holocene rainfall patterns in China

Abstract .. Open access

Proxy-based reconstructions and modeling of Holocene spatiotemporal precipitation patterns for China and Mongolia have hitherto yielded contradictory results indicating that the basic mechanisms behind the East Asian Summer Monsoon and its interaction with the westerly jet stream remain poorly understood. We present quantitative reconstructions of Holocene precipitation derived from 101 fossil pollen records and analyse them with the help of a minimal empirical model. We show that the westerly jet-stream axis shifted gradually southward and became less tilted since the middle Holocene. This was tracked by the summer monsoon rain band resulting in an early-Holocene precipitation maximum over most of western China, a mid-Holocene maximum in north-central and northeastern China, and a late-Holocene maximum in southeastern China. Our results suggest that a correct simulation of the orientation and position of the westerly jet stream is crucial to the reliable prediction of precipitation patterns in China and Mongolia.

https://www.nature.com/articles/s41467-019-09866-8#Fig1

[bligh8]

Larger Increases in More Extreme Local Precipitation Events as Climate Warms

 05 June 2019 https://doi.org/10.1029/2019GL082908

Abstract
Climate models project that extreme precipitation events will intensify in proportion to their intensity during the 21st century at large spatial scales. The identification of the causes of this phenomenon nevertheless remains tenuous. Using a large ensemble of North American regional climate simulations, we show that the more rapid intensification of more extreme events also appears as a robust feature at finer regional scales. The larger increases in more extreme events than in less extreme events are found to be primarily due to atmospheric circulation changes. Thermodynamically induced changes have relatively uniform effects across extreme events and regions. In contrast, circulation changes weaken moderate events over western interior regions of North America and enhance them elsewhere. The weakening effect decreases and even reverses for more extreme events, whereas there is further intensification over other parts of North America, creating an “intense gets intenser” pattern over most of the continent.

The above is something were watching unfold across the central US

Plain Language Summary
Climate models project that extreme precipitation events will intensify during the 21st century at large spatial scales, with several studies suggesting that the most extreme events will exhibit the highest rate of intensification. Identification of the causes of this phenomenon nevertheless remains tenuous, partly because estimating long‐term changes in precipitation extremes is difficult, particularly for precipitation extremes at impact‐relevant spatial scales. Robustly estimated changes in precipitation extremes at small spatial scales can only be obtained from large extreme precipitation data sets from large ensemble simulations. We employ a large ensemble regional climate simulation experiment performed for North America. The large volume of output from this experiment allows us to confidently obtain statistical evidence that precipitation intensification occurs more rapidly with warming for more extreme events at impact‐relevant spatial scales, and secondly, to determine the causes for this phenomenon. The effect of atmospheric moisture increases caused by greenhouse gas warming is found to be similar for extreme precipitation events of different intensities, ranging from 2‐ to 50‐year events. In contrast, atmospheric circulation change due to greenhouse gas warming tends to reduce the effect of the atmospheric moisture increases on less intense events rather than intensifying the effect on more extreme events.

bligh

[bligh8]

U.S. hydrologic design standards insufficient due to large increases in frequency of rainfall extremes

Daniel B. Wright  Christopher D. Bosma  Tania Lopez‐Cantu
First published: 12 July 2019 https://doi.org/10.1029/2019GL083235

Abstract
Evidence for intensifying rainfall extremes has not translated into “actionable” information needed by engineers and risk analysts, who are often concerned with very rare events such as “100‐year storms.” Low signal‐to‐noise associated with such events makes trend detection nearly impossible using conventional methods. We use a regional aggregation approach to boost this signal‐to‐noise, showing that such storms have increased in frequency over much of the conterminous United States since 1950, a period characterized by widespread hydrologic infrastructure development. Most of these increases can be attributed to secular climate change rather than climate variability, and we demonstrate potentially serious implications for the reliability of existing and planned hydrologic infrastructure and analyses. Though trends in rainfall extremes have not yet translated into observable increases in flood risks, these results nonetheless point to the need for prompt updating of hydrologic design standards, taking into consideration recent changes in extreme rainfall properties.

Plain Language Summary
Numerous studies have shown that heavy rainfall in the United States and elsewhere is becoming more common and more severe in a warming climate. These studies have not shown, however, how the most extreme rainfall events are changing, since these storms are so rare that they are difficult to assess using conventional techniques, which generally focus on changes at individual geographic locations. We instead use a simple aggregation technique to “pool” multiple observations within a region. This “pooling” allows us to show that rainfall events that exceed common engineering design criteria, including 100‐year storms, have increased in frequency in most parts of the United States since 1950—a period of widespread infrastructure construction. We show that in most locations, these increases are likely due to climate warming. We also show that much of the existing and planned hydrologic infrastructure in the U.S. based on published rainfall design standards is and will continue to underperform its intended reliability due to these rainfall changes.

This paper is paywalled.... an frankly supports what we already know.

[bligh8]

Recent increase in catastrophic tropical cyclone flooding in coastal North Carolina, USA: Long-term observations suggest a regime shift
https://www.nature.com/articles/s41598-019-46928-9

Hans W. Paerl, Nathan S. Hall, Alexandria G. Hounshell, Richard A. Luettich Jr., Karen L. Rossignol, Christopher L. Osburn & Jerad Bales
Scientific Reports volume 9, Article number: 10620 (2019)...open access

 Abstract

Coastal North Carolina, USA, has experienced three extreme tropical cyclone-driven flood events since 1999, causing catastrophic human impacts from flooding and leading to major alterations of water quality, biogeochemistry, and ecological conditions. The apparent increased frequency and magnitudes of such events led us to question whether this is just coincidence or whether we are witnessing a regime shift in tropical cyclone flooding and associated ecosystem impacts. Examination of continuous rainfall records for coastal NC since 1898 reveals a period of unprecedentedly high precipitation since the late-1990’s, and a trend toward increasingly high precipitation associated with tropical cyclones over the last 120 years. We posit that this trend, which is consistent with observations elsewhere, represents a recent regime shift with major ramifications for hydrology, carbon and nutrient cycling, water and habitat quality and resourcefulness of Mid-Atlantic and possibly other USA coastal regions.

" In addition to their devastating societal and economic impacts, storms associated with this increased frequency are having major ramifications for carbon and nutrient cycling in coastal estuaries and thus represent “hot moments” in coastal biogeochemistry7. In fact, recent work shows that these extreme events caused unprecedented nutrient- and organic matter-laden freshwater discharges to nutrient-sensitive receiving coastal waters, including the USA’s 2nd largest estuarine complex and a key fishery and recreational resource, the Albemarle-Pamlico Sound (APS) (Fig. 1), which drains ~ 40% of North Carolina’s and 10% of Virginia’s coastal plain regions via 5 major rivers8,9."

"Overall, our analysis indicates that; 1) we are experiencing a regime shift in the intensity and quantity of rainfall associated with these events, and 2) this shift has led to unprecedented large loads of nutrients and orgenic matter with major implications for biogeochemical cycling, primary production and overall water quality conditions in the receiving APS and adjacent coastal waters. Furthermore, our observations are consistent with similar observations elsewhere and with predicted hydrologic, nutrient and carbon flux changes taking place in a warming climate1,2,3,4,5,6."

"The receiving waters of the APS have a surface area of 5,335 km2 and drain five major watersheds (Neuse, Tar-Pamlico, Roanoke, Chowan, and Pasquotank Rivers). These watersheds cover an area ~80,000 km2, total freshwater discharge of ∼21 km3 yr−1, and drain about 40% of North Carolina’s and 10% of Virginia’s surface area. Because tidal exchange with the coastal Atlantic Ocean is restricted to three narrow inlets, the APS has a relatively long water residence time of ~1 yr14; this provides suspended algae (phytoplankton) and vascular plants ample time to assimilate nutrients, resulting in high productivity per unit nutrient input. These characteristics are key to the PS serving as a highly productive nursery, supporting ~80% of US mid-Atlantic commercial and recreationally caught finfish and shellfish species11. However, it also makes the system sensitive to nutrient-over enrichment, resultant eutrophication and nuisance algal blooms12,15. The long residence time also enables ample time for photochemical and/or microbial degradation of organic matter16."

"With less than a 2% chance of three such events occurring in a twenty-year period23, either North Carolina has been very unlucky, or the historical record used to define the storm statistics is no longer representative of the present climatic regime. This analysis suggests that the occurrence of three extreme floods resulting from high rainfall tropical cyclone events in the past 20 years is a consequence of the increased moisture carrying capacity of tropical cyclones due to the warming climate

"Thus, evidence is accumulating that we may also be seeing changes to the “system state” of coastal waters in terms of their ability to capture or release CO2 37,38. Such changes caused by an increased frequency of extreme storm events are ostensibly reorganizing coastal carbon cycles

"Considering these extreme precipitation events and their hydrologic and biogeochemical consequences in totality, it is clear that they are unparalleled in the past 120+ years of recorded tropical cyclones in coastal North Carolina (Fig. 3). The potential exists for receiving waters globally to undergo unprecedented perturbations to nutrient and carbon cycling, fisheries habitat and sustainability due to increasing frequency of extreme precipitation events; all of which are still to be determined. With roughly 40% of the world’s population within 100 km of the coast, development inland, as well as along the coastline, will exacerbate the perturbations caused by this type of regime shift.....more within the paper