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) 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 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.

Thursday, May 22, 2014

Message in a bottle

Walking to the waters edge with messages-in-a-bottle

Christine and I were married on July 15, 2006 at Crescent Beach on the Strait of Juan de Fuca. As part of our ceremony we asked those in attendance to write short messages about the day, or our marriage, or really whatever they wanted. We stuck all of those messages in two wine bottles, corked them, and sealed them with melted wax. Then, at the end of the ceremony, we walked to the waters edge and flung them into Crescent Bay:

I recall that some of our friends and loved ones were a bit surprised: We weren't going to read them first? We didn't, and I think in our minds, we just wanted the ocean to hold all of those messages of love and inspiration for us. But now we have a chance to read at least some of them, 8 years later...

One of the bottles lying on Arcadia Beach in Oregon. Photo by Christine Webber

On April 28th we received an email from Christine Webber, who was travelling through Oregon and happened to stop at the beach. And, incredibly, she found one of our bottles on the beach (see her wonderful blog post about the bottle here). Unbelievable! I am a big fan of messages in bottles and have sent many of them into the ocean throughout my life. When I was young and my dad would go to sea with the Navy I would sometimes send bottles with him to throw overboard once they were clear of the coast. But never has one actually come back.

The bottle, freshly tossed ashore by Neptune. Photo by Christine Webber

What journey did that bottle take? In the past I may have let that question rest and perhaps even might have chalked it up to some mythic intent of the ocean...but now I am all about lets dig into this a bit. We tossed the two bottles into Crescent Bay it was the middle of July, and during most of the summer the Strait of Juan de Fuca is characterized by an outward directed residual flow. This is characteristic of estuaries, and the Strait of Juan de Fuca is indeed part of the massive estuary that we know as the Salish Sea:

Map of the Salish Sea & Surrounding Basin, Stefan Freelan, WWU, 2009

The residual flow is the mean longer-term (i.e. over weeks) flow, which averages out the back-and-forth currents associated with tidally-generated currents. Here, for example, is a beautiful animation of surface salinity in the Salish Sea derived from a numerical hydrodynamic model...and if you watch this a few times you can start to see the residual flow laid over top of the fact this animation is sped up so much that the oscillating tidal currents are barely even perceptible:

Numerical model by the MoSSea Program

Work by Thomson and others (2007) estimated that those outward directed residual surface currents in the Strait of Juan de Fuca can average an astonishing 0.5 m/s...or just shy of 1 knot. This suggests the possibility that it only took the bottle a few days to make its way out of the Strait of Juan de Fuca, since it is ~200 km from Crescent Bay to the shelf edge off the coast of Washington or Vancouver Island.

How about from there? This is where things get fun...I turned to a tool called OSCURS (Ocean Surface Current Simulator). Oceanographic models are generally fairly elaborate constructs, and may require both considerable expertise and computing power to run. I view OSCURS as something like an oceanographic model for the people, since it is very simple and runs online. And its got some chops - its driven by measured surface pressure, and has been used to understand and model the movement of everything from fish larvae to debris in the ocean. And when I plugged in a starting point outside the mouth of the Strait of Juan de Fuca, set it up with the appropriate start and end date, and played a bit with the parameters (which let you sort of "tune" the model for the type of item drifting on the ocean's surface), I got the following:

OSCURS trajectory for a drifting object released from the mouth of the Strait of Juan de Fuca on 20 July 2006.

Now, you can see that OSCURS is far from perfect. Somehow this bottle is supposed to end up deep in the Yukon Territory? Furthermore, by tweaking the parameters I can make this bottle end up inside China:

But at the very least OSCURS allows one to dream of the things that this bottle may have experienced on its 8-year journey. Even if (and this is a possible, and even probable, path) it washed up on Crescent Beach a few hours after our wedding, sat in the high intertidal undisturbed for almost 8 years, and was finally dislodged and sailed down the coast by the California Current just the spring, its still amazing that it made the journey at all and is now back in our possession.

Tuesday, April 15, 2014

An updated Elwha river mouth timelapse

A year or so ago I posted a timelapse of the Elwha River mouth using both historical aerial photography and Andy Ritchie's PlaneCam orthoimages of the Elwha system. In preparation for a few talks, and a paper in prep, and to help me wrap my brain around the changes we are seeing these days, I updated the timelapse a bit. Enjoy:

Monday, April 7, 2014

Tracking shorelines

The map above motivates me. This is a screen grab from the NANOOS Beach and Shoreline Change site, showing shoreline monitoring sites in Washington State. Kudos to NANOOS for including data on shoreline change in their incredible site (which is a compendium of all things related to oceanography data) - but the map makes it clear that we in Washington State are dropping the ball when it comes to understanding trends related to shoreline morphology.

Proposed locations of shoreline monitoring on the Olympic Peninsula

As part of my program I've proposed and am developing a small scale shoreline monitoring program for the Olympic Peninsula. Why small-scale? Well because its just me, and this is a big area. But something is better than nothing. Working with a bunch of partners (Olympic National Park, the Quileute Tribe, the North Olympic Peninsula Skills Center Natural Resources Program, the Quilayutte Valley School District, Pacific Coast Salmon Coalition, the North Pacific Coast Marine Resources Committee, US Coast Guard, the Jamestown S'Klallam Tribe, the Lower Elwha Klallam Tribe and the US Fish and Wildlife Service) I've been able to either start developing or collecting data on a bunch of the proposed sites in the map above.

The partnership with the QV School District, the Skills Center, the MRC and the Pacific Coast Salmon Coalition is particularly valuable because it has allowed us to get students involved:

Students surveying Rialto Beach, Olympic National Park

A growing body of evidence supports the idea that engagement in research experiences early in students' academic career provides positive benefits, so this is a great opportunity to use this program to support Olympic Peninsula students. Why do it at all though? Well - my primary motivation regarding monitoring shoreline morphology is that we expect shorelines to change in increasingly unusual ways due to climate change. Here, for example, is a schematic describing one model of how shorelines respond to sea level rise:

In general, we expect shorelines to move landward under rising seas, and this will likely be associated with steepening and coarsening of the beach. This has all sorts of ecological implications - but my primary motivation here is how that will change the beach's protective capacity. Beaches are barriers - protecting human communities from the ocean, and it is likely going to become more difficult for beaches to provide those buffering services to communities in the coming decades.

The figure above is from an analysis of climate-related vulnerabilities for the Olympic Coast National Marine Sanctuary, and is designed to show the potential change to the water level histogram (this is the distribution of all water levels that the coast experiences over a longer time a few months or more) due to both sea level rise, storms and changes to the outer coast wave climate. The point is that under climate change projections, the upper part of the beach will come into contact with the ocean much more frequently, which could promote flooding and erosion.

However, one thing is already clear from working on the outer coast...beaches change dramatically all of the time:

Above, for example, are two beach profiles from Rialto Beach, one collected in the Fall of 2012 and the other in the spring of 2013. These (preliminary) data suggest that over the winter the beach built outwards by ~10 m! For those that know this coast this is hardly surprising, indeed there is significant beach change observable in the much shorter record captured by this time lapse video shot around Mosquito Creek (this was shot to document the removal of the Misawa Dock associated with the Tohoku tsunami debris). But characterizing the rates and patterns of change in advance is crucial to being able to pick out erosion signals that are unusual in the future.