Tuesday, August 26, 2014

Sub-tidal observations of sea star wasting disease

A piece of a sea star, apparently Pycnopodia helianthoides, observed at approximately 45 foot depth in Port Angeles harbor on 20 August 2014

The Elwha sub-tidal SCUBA surveys that I participate in are designed first and foremost to help us understand how the Elwha dam removal influences the marine biological community in the nearshore areas adjacent to the Elwha River mouth. This year, though, we were also interested in any observations that might help us to understand how Sea Star Wasting disease is influencing sub-tidal sea stars in the central Strait of Juan de Fuca. Much of what has been reported on recently from the central Strait of Juan de Fuca is based on intertidal observations.

The synopsis: We definitely observed apparently infected stars (mostly, if not all, Pycnopodia helianthoides). We also observed plenty of apparently health stars (including Pycnopodia helianthoides), in some cases right next to, or near, dying stars. Some photos and video are below, collected at the sites shown on the map below, between 5 and 20 August 2014.

Our next step, hopefully, will be to use our baseline data from as far back as 2008 to test the hypothesis that some sea star species have declined in density in the past year at our sub-tidal sites in the Strait of Juan de Fuca.

Video shot at site D2 showing a dead or dying Pycnopodia helianthoides.

An apparently healthy Pycnopodia helianthoides from site D2.

Video shot at site F2 showing both an apparently healthy Dermasterias imbricata and a dead or dying Pycnopodia helianthoides.

An apparently healthy Pycnopodia helianthoides at site E2

A dead or dying Pycnopodia helianthoides photographed at the site marked "PA Harbor". This was near to the sea star leg shown in the photograph at top of this post, though it wasn't clear if the two photos were of parts of the same star.

An apparently healthy Evasterias troschelii at site J1

Wednesday, August 6, 2014

Nuisance Flooding and sea level rise

Nuisance flooding in Port Orchard, WA on January 6, 2010. Photo by Ray Garrido, courtesy of Washington Department of Ecology.

NOAA just released a brilliant analysis of patterns of "nuisance flooding" along the US coast. The report analyzes hourly water level records from 45 tide gauges around the country that:

1) have at least 30 years of more-or-less continuous water level data

2) have a "minor flood" elevation threshold defined by the National Weather Service.

The report also defines "nuisance" flooding as coastal water elevations that exceed that "minor flood" elevation as it is set by the National Weather Service, and are typically associated with "minor coastal flooding impacts". So we are talking about stuff like is shown in the photo above from Port Orchard...not just the catastrophic flooding associated with events like Superstorm Sandy or Hurricane Katrina. It turns out that this sort of nuisance flooding, while it doesn't get much media attention, happens all the time:

Average number of days per year with nuisance flooding for 2007-2009 for 45 US tide gauges. Figure 2 from Sweet et al 2014.

In the report they analyzed a variety of different components of flooding, including trends over time (expressed both as cumulative hours of flooding during the year, as well as individual days that flooding occurred), seasonal patterns (i.e. when during the year flooding tends to occur), and the contribution of various factors (astronomic tides, changes in mean sea level and non-tidal residuals) to driving total water levels that result in nuisance flooding. Here is an example for Charleston, SC which, like many east coast sites, has experienced fairly dramatic changes in patterns of nuisance flooding over the last century:

Figure from Appendix 2 of Sweet et al 2014 showing (top left)nuisance flood events (cumulative hours and impacted days) per meteorological year plotted with annual mean sea level, (bottom left) return level interval curves, (top right) maximum water levels (black) per calendar day over the 1980‐2009 period decomposed into a low‐frequency MSL cycle (blue dot), predicted tide (blue; no Sa and Ssa harmonic fits) and nontidal residual (NTR; green), and (bottom right) average nuisance flood events (shared y-axis) by calendar month over 1980‐2009.

I was particularly interested in the fundamental analysis in the upper left, and in particular the cumulative hours of the meteorological year (May of a year to April of the next, so winter is included) during which a minor flood threshold is exceeded. In their analysis only two of Washington's tide gauges were included. Seattle and Toke Point in the mouth of Willapa Bay. Here is Seattle:

A few things jump out - in most cases the rising occurrence of nuisance flooding is related to rising relative sea level, as is seen in the Charleston SC example above, as well as in Seattle. This isn't surprising - rising relative sea level means that the average level of the water is rising relative to the land, so flooding should occur. I was able to replicate their analysis process using data downloaded from NOAA, and also added a 10-year running average of the number of hours per year for which water level exceeded the nuisance flood threshold:

and ran it for Toke Point:

here, over the period of measurement (starting in 1979) there has been little to no systematic trend in relative sea level. Perhaps as a result, there is not clear pattern related to changing nuisance flood frequency.

I found only one other station that included enough hourly data to make this analysis worthwhile - Neah Bay - and applied Seattle's nuisance flood elevation threshold:

here, FALLING relative sea level has apparently resulted in a pattern of falling nuisance flood frequency. You can also start to see an apparent relationship between the average flood frequency (the black line), and annual mean sea level. Here is what it looks like for Seattle when they are plotted together:

This is a potentially useful tool, since it gives us a way to assess how many extra hours of flooding to expect for a given amount of relative sea level rise. I haven't done any formal analysis on this, but loosely it looks like relative sea level rise of about 10 cm leads to maybe about an extra hour of flooding over the course of the year, on average, in Seattle.

Sadly, most other stations in Washington don't have enough available hourly data to make this analysis worthwhile. Here is Port Angeles, for example:

There are a few interesting things here - the high water levels associated with the 1998 El Nino really stand out, but that year didn't see water levels exceeding the nuisance flood threshold. The big year for that was 2005, even though average sea level that year was almost 10 cm lower than in 1998. This is probably because of the importance of other factorss, including chance, in driving flooding in our area. Our large tidal ranges and complex tidal signal mean that a variety of factors have to line up to drive water level up into the nuisance flood realm - something along the lines of a big storm with low pressure, aligning with a spring tide period and a high tide. Rising relative sea level in the background really helps to exceed the nuisance flood threshold more frequently. Overall, in this case though, the record really isn't long enough to detect trends given all the variability.

Its also worth nothing that the "nuisance flood" threshold used here is somewhat arbitrary. In the NOAA report its an elevation that the National Weather Service has identified as being associated with "minor coastal flooding impacts". But if your home, or some important piece of infrastructure, is below that threshold, then you would see flooding more frequently then is suggested by this analysis. But the overall patterns should still hold up...

Friday, August 1, 2014

Evolution at the Elwha River delta in pictures

I am a big fan of timelapse as a tool for visualizing coastal change. I had the opportunity today to recover photos from a camera that has been looking down at the Elwha River delta since 2011, and put together this annual time series to capture the scale of change. These images were all captured when the water level was between 0.9 and 1.0 m relative to MLLW (as measured in Port Angeles), which makes it easier for the eye to register change, as compared to when the tidal signal is included in the time lapse. Here is an example of what I mean.

Here is today's view:

and this one from 2013 - same day of the year, same water level:

and then the earliest one I will show here, from 2012 (since there really isn't any detectable change between summer 2011 and 2012 in these photos:

Note in the above that the photo timestamp is incorrect. This is, in fact, from 2012.

and here are all three together:

The photo from summer 2013 is a bit mis-leading, since it suggests a relatively small scale of change. But again, the August 2013 photo from above is taken at a water level of ~1m above MLLW. Here is one shot when water level was 0.0 m MLLW (at 6am on 2 August 2013):

You can see here that the scale of change was quite dramatic, but the new delta deposits hadn't built up in elevation to the extent that they have by this point.

A few other views from today:

Thursday, July 24, 2014

Views from the Strait of Juan de Fuca

Pterygophora californica, in the stiff "breeze" that is all too common at Elwha dive sites

This week marked the beginning of another year of sub-tidal surveys designed to track the response of the marine biological community to the removal of the Elwha Dams. And for the most part, after two years of (not surprisingly) pretty poor visibility, reasonably good visibility is back, with some sites that I had the chance to dive providing visibility in excess of 20 feet. Which also means that we are collecting more good photography and video. So here, all shot at sites around the Elwha delta and fresh off the SD card, are a few for you to enjoy.

Pterygophora californica stipe, hosting its own micro-community

Urticina columbiana in the surge

Terebellid worm

the enchanting Balanus nubilus

the cryptic Saxidomus gigantea

Metacarcinus gracilis - I always need to check twice to make sure its not a Dungeness

Pagarus armatus, with a diver in the background

a multi-species cluster: Eudistylia vancouverii, Schizobranchia insignis and (possibly) Eudistylia polymorpha

Probably Citharichthys, utilizing the newly sandy habitat at our site 4SP1 near the mouth of the Elwha

Tuesday, July 1, 2014

An El Nino winter on the coast?

NOAA,s Climate Prediction Center is projecting a strong probability of El Nino conditions developing this summer and persisting at least through winter. Should this happen, and particularly, should strong El Nino conditions develop, it could mean a winter of frequent coastal flooding and possible shoreline erosion in the inland waters of Washington State.

First off, what is an El Nino? At its root, El Nino is related to a relaxation of the trade winds that girdle the globe at near-equatorial latitudes.

A nice short description of global atmospheric circulation and the trade winds by Dr. Keith Meldahl of Mira Costa College

This relaxation of the trade winds, in the simplest sense, allows warm equatorial ocean water that is typically forced to the western side of the Pacific basin to "slosh" back to the east. And this has a variety of important consequences on our coast on the eastern side of the Pacific Ocean basin, including increased sea water temperatures and sea level. Sea water temperatures influence things like ocean productivity and the occurrence and distribution of organisms. In our area, El Nino tends to be associated with some pretty interesting appearances of rare or anomalous organisms.

The water level consequences, though, are what I want to focus on here. El Nino are associated with elevated mean water levels. For example, here are the average mean monthly water levels (relative to MLLW) for Port Angeles and Neah Bay (top panel below) as reported by NOAA's Center for Operational Products and Services:

So there are a variety of patterns of interest in the top panel - first you can see that mean sea level (this is the average of all recorded water levels over every month) varies over the course of a year, with higher sea levels in winter versus summer (on the order of ~20 cm higher in winter for Port Angeles and Neah Bay). This is why we tend to see more flooding in winter versus summer in our area, even though the astronomical tides reach very similar elevations in the two season. Your eye might also be able to register the pattern of falling relative sea level in Neah Bay on this graph, that is probably due in large part to vertical uplift of the earth's surface there.

The bottom panel shows the same data, but with the average seasonal water level pattern removed from the data in the top panel (and also only shows the time period for which the two datasets overlap)...so this essentially shows you how much mean water level is different from the long-term average. And this is where the two strong El Ninos in the record, in 1983 and 1998, really pop out (I've also circled them in blue). So during both of those events the PNW experienced multiple months of water levels that were ~ 30 cm above average...thats over a foot! That matters, especially in the winter when it gets added to the typically ~20 cm of elevated water level. The coastal impacts of the 1983 and 1998 El Nino are poorly documented in Washington State, but even the weak El Nino in 2010 caused concern in our area.

As of yet the strength of the El Nino that appears likely to develop isn't clear...but given the relative sea level rise patterns in Puget Sound, any extra mean water level added on top of rising seas is bound to get some notice.

Tuesday, June 24, 2014

Learning more about Discovery Bay

Students from the UW MeSSAGE program log a core pulled from the Discovery Bay salt marsh

Discovery Bay on the Strait of Juan de Fuca in Washington State is one of the most important sites in this area from a coastal hazards standpoint. Why? Because written in the sediments of the salt marsh at the head of the bay is a record of multiple tsunamis, that are manifested as sand layers sandwiched between layers of peat:

Tsunami sand layer in the bank of Salmon Creek, which cuts through the salt marsh at the head of Discovery Bay

I've visited the Discovery Bay marsh on multiple occasions, and written in more detail about the background of the site and tsunami risk in Washington State in general. On 20 June 2014, though, I had my first opportunity to go out, in partnership with students and faculty from the UW MeSSAGE Program, Carrie Garrison-Laney (a graduate student at UW), and Ron Tognazzini (a retired earthquake engineer) and actually collect some data at the marsh in an effort to better understand the site and how it has been impacted by tsunamis.

Carrie Garrison-Laney, a UW graduate student focused on tsunami sedimentology, talks to a group of students from the UW MeSSAGE Program after the field day.

Having that many people on the marsh allowed us to really spread out and core a variety of sites around the marsh:

Core sites in the Discovery Bay marsh on 20 June 2014

At each sites students pulled cores of the marsh - in some cases the cores were 3 meters long - and then painstakingly described the stratigraphy of each core in terms of grain size and sedimentology. Additionally, a few samples were collected for carbon-14 analysis. The goal - improve our understanding of the dates of events recorded in the sediment, and also potentially understand something about the dynamics of events by trying to connect layers across the entire marsh.

A coring team at work

A potential tsunami layer exposed in the core barrel after being pulled from the marsh

Thursday, May 29, 2014

A new pulse of tsunami debris?

A piece by King 5 news from 26 May 2014 investigating reports of another pulse of debris on SW Washington beaches

Recent media reports suggest that a new pulse of debris - some of it probably from the Tohoku tsunami, is littering beaches in Washington. There is the implication in these reports that this, finally, could be the leading edge of the massive wave that has been feared all along...but for the reasons below I am going to argue that this probably isn't the case.

Animation, based on numerical ocean modelling, of debris transport in the North Pacific following the March 2011 Tohoku Tsunami. Courtesy of the International Pacific Research Center

First off, if you watch the model results above (get the full suite of model animations here), you note that they suggest that as of right now, the highest concentration of debris appears to be far off the coast of California and Oregon, but that there are episodic "tongues" that are advected up towards the coast of Washington, B.C. and even Alaska. This is perhaps most obvious if you break out individual windage classes shown combined in the video above. Here, for example, are results from the "2% windage class" alone (see this white paper on how the modellers defined the various windage classes":

These model results are consistent with observations from our coast. Debris has seemed to arrive in pulses, and my overall impression based on the last three years is that late spring/early summer is a very likely time to see pulses of debris. Here is a media report, for example, from June 2012 investigating a general increase in the debris load, and June 2012 was when a large dock washed up on Oregon's Agate Beach. I reported on a June 2012 pulse in a talk given as part of the Olympic National Park's Perspective series based on the monitoring and clean-up work done by Russ Lewis on the SW WA coast...here is the slide:

Early summer of 2013 was quieter, but not without some apparent pulses. Here is the report from Russ from June 12 2013, "There was an uptick in long range debris overnight as there was a noticeable number of plastic bottles, small chunks of s-foam, some light bulbs, a few small fishing floats, larger plastics and also some local stuff in the mix such as rope, plastic bags". Why might late spring/early summer be associated with pulses of debris? It likely relates to the seasonal variation in near coastal winds, and its influence on currents along the west coast of the U.S.

Part of what motivated me to write this blog was my own brush with a suspected debris item, found May 14th banging around on the rocks in the high intertidal zone at San Juan County Park on the west side of San Juan Island. Its not clear to me what this was back before it was marine debris:

but when I flipped it over it was carrying the signature of a long ocean voyage - a heavy load of Lepas anatifera, also known as the Pelagic Gooseneck Barnacle:

and the evidence that it came from Asia? Clusters of large mussels that I have tentatively identified as being Mytilus galloprovincialis:

This species is native to the Mediterranean but is raised widely in Asia for food. This species occurred on the dock that washed up on Washington's coast a year and a half ago, and while it does occur as an invasive in Puget Sound, in combination with the Pelagic Gooseneck barnacles it suggests the possibility of Asian origin.